Next Article in Journal
The Relationship of Anthropometric Characteristics and Motor Abilities with Vortex Throwing Performance in Young Female Track-and-Field Athletes
Previous Article in Journal
Industrial Site Selection: Methodologies, Advances and Challenges
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Applied Sciences
Volume 15
Issue 21
10.3390/app152111380
applsci-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Ultra-Deep Oil and Gas Geological Characteristics and Exploration Potential in the Sichuan Basin

by
Gang Zhou
1,
Zili Zhang
1,
Zehao Yan
2,*,
Qi Li
2,
Hehe Chen
2 and
Bingjie Du
2
1
Petro China Southwest Oil & Gasfield Company Exploration and Development Research Institute, Chengdu 610041, China
2
School of Ocean Sciences, China University of Geoscience, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(21), 11380; https://doi.org/10.3390/app152111380
Submission received: 4 August 2025 / Revised: 6 October 2025 / Accepted: 7 October 2025 / Published: 24 October 2025
Browse Figures
Review Reports Versions Notes

Abstract

Judging from the current global exploration trend, ultra-deep layers have become the main battlefield for energy exploration. China has made great progress in the ultra-deep field in recent decades, with the Tarim Basin and Sichuan Basin as the focus of exploration. The Sichuan Basin is a large superimposed gas-bearing basin that has experienced multiple tectonic movements and has developed multiple sets of reservoir–caprock combinations vertically. Notably, the multi-stage platform margin belt-type reservoirs of the Sinian–Lower Paleozoic exhibit inherited and superimposed development. Source rocks from the Qiongzhusi, Doushantuo, and Maidiping formations are located in close proximity to reservoirs, creating a complex hydrocarbon supply system, resulting in vertical and lateral migration paths. The structural faults connect the source and reservoir, and the source–reservoir–caprock combination is complete, with huge exploration potential. At the same time, the ultra-deep carbonate rock structure in the basin is weakly deformed, the ancient closures are well preserved, and the ancient oil reservoirs are cracked into gas reservoirs in situ, with little loss, which is conducive to the large-scale accumulation of natural gas. Since the Nvji well produced 18,500 cubic meters of gas per day in 1979, the study of ultra-deep layers in the Sichuan Basin has begun. Subsequently, further achievements have been made in the Guanji, Jiulongshan, Longgang, Shuangyushi, Wutan and Penglai gas fields. Since 2000, two trillion cubic meters of exploration areas have been discovered, with huge exploration potential, which is an important area for increasing production by trillion cubic meters in the future. Faced with the ultra-deep high-temperature and high-pressure geological environment and the complex geological conditions formed by multi-stage superimposed tectonic movements, how do we understand the special geological environment of ultra-deep layers? What geological processes have the generation, migration and enrichment of ultra-deep hydrocarbons experienced? What are the laws of distribution of ultra-deep oil and gas reservoirs? Based on the major achievements and important discoveries made in ultra-deep oil and gas exploration in recent years, this paper discusses the formation and enrichment status of ultra-deep oil and gas reservoirs in the Sichuan Basin from the perspective of basin structure, source rocks, reservoirs, caprocks, closures and preservation conditions, and provides support for the optimization of favorable exploration areas in the future.

1. Introduction

With years of oil and gas exploration and development, discovering hydrocarbon resources at shallow and intermediate depths has become increasingly challenging. As a result, ultra-deep oil and gas exploration has become a global focus [1], representing the inevitable path for future hydrocarbon development. Significant breakthroughs have been made worldwide, including major discoveries in ultra-deep reservoirs in the Gulf of Mexico, deep-water basins along the East African continental margin, and the Santos Basin in South America [2,3]. In Europe, ultra-deep exploration has primarily targeted deep- and ultra-deep-water regions, with substantial reserves confirmed in the Eastern Mediterranean [4]. To date, 129 ultra-deep oil and gas fields have been discovered globally, demonstrating vast potential for proven and prospective reservoirs. China has also entered the ultra-deep exploration phase, achieving significant successes [5,6], with current efforts concentrated in the Sinian to Lower Paleozoic formations of the Sichuan and Tarim Basins [7]. In western China’s petroliferous basins, conventional deep reservoirs are buried at depths of 4500–6000 m, while ultra-deep reservoirs exceed 6000 m [8]. Compared to international counterparts, China’s ultra-deep reservoirs are generally deeper and pose greater exploration challenges.
The Sichuan Basin is a large superimposed gas-bearing basin developed on a craton [9,10]. From the Sinian to Middle Triassic, it was dominated by marine carbonate deposition, with thicknesses ranging from 4000 to 7000 m. Among China’s three major cratonic basins, the Sichuan Basin exhibits distinct advantages in depositional duration, development time, and sediment thickness [11]. Multi-stage mound–shoal complex bodies of Sinian–Lower Paleozoic age are well-developed in the Deyang–Anyue Rift Trough, Central Sichuan Paleo-Uplift, and its slope zones. The basin contains numerous ultra-deep target formations, with major gas fields already discovered, including Puguang, Yuanba, Anyue, Longgang, and Chuanxi [12]. These discoveries highlight its substantial resource potential, low exploration maturity, and promising future prospects.

2. Geological Background

2.1. Regional Setting and Stratigraphic Fill Patterns

The Sichuan Basin has long been situated in the transitional zone between the Laurasia and Gondwana [13]. As a sedimentary basin developed on the northwestern margin of the Yangtze Craton, it exhibits a distinct rhombic structure bounded by the Longmenshan, Daliangshan, Daloushan, Qiyueshan, Dabashan, and Micangshan, all of which have subjected the basin to intense compressional forces from multiple orogenic belts (Figure 1).
Additionally, the basin has been influenced by multiple tectonic events, including the Chengjiang, Tongwan, Caledonian, Yunnan, Dongwu, Indosinian, Yanshan, and Himalayan movements (Figure 2). These superimposed tectonic phases have resulted in differential evolution across different regions: foredeep depressions developed in the western and northern Sichuan Basin, fold-thrust structures dominate the eastern and southern regions, while the central Sichuan area remained a stable uplift zone [14]. This structural differentiation has led to a vertically stratified and laterally zoned geological architecture in the ultra-deep strata of the Sichuan Basin, with varying structural styles across different regions, thereby forming diverse hydrocarbon accumulation assemblages [1].
Applsci 15 11380 g001
Figure 1. Location of Sichuan Basin on Yangtze Craton [15].
Figure 1. Location of Sichuan Basin on Yangtze Craton [15].
Applsci 15 11380 g001
Applsci 15 11380 g002
Figure 2. Stratigraphic and Tectonic Cycle Correlation of Sichuan Basin [16].
Figure 2. Stratigraphic and Tectonic Cycle Correlation of Sichuan Basin [16].
Applsci 15 11380 g002

2.2. Tectonic Evolution and Stratigraphic Fill Characteristics of Ultra-Deep Strata

Since the Neoproterozoic, the Sichuan Basin has undergone six major tectonic cycles: the Yangtze, Caledonian, Hercynian, Indosinian, Yanshan, and Himalayan. The Sinian to Upper Paleozoic strata were primarily shaped by the Yangtze, Caledonian, Hercynian, and Indosinian cycles.
  • Yangtze Cycle
The Yangtze Cycle represents a late Proterozoic orogenic phase, subdivided into three tectonic episodes: the Jinning, Chengjiang, and Tongwan movements (Figure 2) [17]. The crystalline basement formed during the Meso-Neoproterozoic was folded and uplifted during the Jinning Movement, forming the folded basement of the Upper Yangtze Craton. Subsequent Chengjiang Movement resulted in an unconformity between the Sinian and pre-Sinian basement, finalizing the basement configuration [18].
The Tongwan Movement, consisting of three episodic phases during the Sinian–Early Cambrian, significantly influenced ultra-deep hydrocarbon accumulation [19]. It created unconformities between the second and third members of the Sinian Dengying Formation, the fourth member of the Dengying Formation and the Cambrian Maidiping Formation, and between the Maidiping and Qiongzhusi Formations [20]. Regional uplift exposed the carbonate platforms of the Deng-2 and Deng-4 members to meteoric dissolution, forming extensive high-quality weathering crust reservoirs. In the late Neoproterozoic, the Proto-Tethyan continental rift extended into the craton, forming the embryonic Deyang–Anyue Rift Trough, which led to the widespread distribution of the Dengying Formation platform margin along its eastern flank. During the second phase of the Tongwan Movement, differential uplift between the Weiyuan and Longnüsi areas created ~70 m of erosional disparity. Inherited basement faulting between the Gaoshi-1 and Wei-28 wells facilitated continued rift trough development, infilled with high-quality source rocks from the Doushantuo, Deng-3, Maidiping, and Qiongzhusi Formations, laying the foundation for ultra-deep reservoirs [21,22].
2.
Caledonian Cycle
The Caledonian Movement occurred from the Cambrian to the end of the Silurian (Figure 2), marked by the closure of the Proto-Tethys Ocean and a shift from regional extension to compression. Basement faulting within the Upper Yangtze Block caused relative uplift in the Leshan–Anyue–Nanchong area, forming the incipient Central Sichuan Paleo-Uplift, which continued developing during the Ordovician–Silurian. High-energy Cambrian mound–shoal reservoirs were distributed around this paleo-uplift [23]. During this period, the Deyang–Anyue Rift Trough entered a filling stage. A major transgression during Qiongzhusi Formation deposition deposited thick, high-quality source rocks within the trough. In the early Canglangpu Formation, incomplete infilling created a “western erosion, eastern deposition” pattern, with carbonate platform deposits dominating the east. High-energy platform margin facies in the Canglangpu Formation formed excellent reservoirs directly overlying the Qiongzhusi source rocks [24].
3.
Hercynian Cycle
During the Devonian–Permian Hercynian period, the tectonic–sedimentary evolution of the Sichuan Basin was predominantly characterized by marine transgression and expansion. Early continental rift activities, coupled with the expansion of the Paleo-Tethys Ocean, triggered subsidence along the basin margins. Based on pre-existing structures, the Songpan–Garze Marine Basin developed in the west, the South Qinling Marine Basin in the north, the Western Hunan–Hubei Marine Basin in the east, and the Southern Sichuan Marine Basin in the south, forming a sedimentary pattern of alternating troughs and platforms. Under this background, the Carboniferous strata in northwestern and eastern Sichuan entered a phase of marine sedimentation. Late Hercynian extension along the Longmen Shan Fault formed multi-phase Permian rift troughs, with high-quality carbonate platform reservoirs distributed along their margins. A major transgression during early Middle Permian Maokou Formation deposition was followed by regional regression in the late Maokou-2 to Maokou-3 periods, enhancing hydrodynamic conditions [25]. This facilitated the development of grain shoal reservoirs in the Maokou-2 member, which, together with the Qixia Formation, constitute key ultra-deep exploration targets [26].
By the Late Triassic, the basin transitioned to terrestrial deposition. Rapid Yanshanian uplift of the Longmen, Micang, and Daba Mountains induced foredeep subsidence, accumulating thick continental strata in western and northern Sichuan. The Himalayan Movement, the most intense orogenic phase, significantly reshaped hydrocarbon distribution [27]. While it reactivated deep faults in the northwestern thrust belt, causing paleo-reservoir disruption, foreland areas (e.g., Shuangyushi) and southeastern slopes remained less affected.

3. Database and Methodology

3.1. Data Source

The data results presented in this paper, including those pertaining to source rocks and resource volumes, as well as interpreted cross-sections and planar maps, are primarily derived from the latest research and statistical findings by the Exploration and Research Institute of PetroChina Southwest Oil & Gasfield Company on favorable deep to ultra-deep exploration intervals in the Sichuan Basin. Supplementary data were obtained through a review of published literature and the IHS Energy Reserves Bulletin.

3.2. Deep and Ultra-Deep Oil and Gas Resource Potential

According to the 2019 petroleum resource assessment under China’s Thirteenth Five-Year Plan by PetroChina, the total resources of deep conventional natural gas in major basins are estimated at 23.65 trillion cubic meters. Of this, the Sichuan Basin accounts for 8.28 trillion cubic meters, representing 35% of the total. The overall conventional natural gas resources in the Sichuan Basin amount to 14.33 trillion cubic meters, with deep to ultra-deep resources contributing 9.68 trillion cubic meters, or 67.56% of the basin’s total.
In 2024, based on current research regarding geological conditions, resource potential, and data availability, Huang et al. [28] identified 40 prospective exploration plays across four major domains: Marine Carbonate Rocks, Foreland Thrust Belt, Deep Shale Gas, as well as Clastic Rocks and Complex Lithostratigraphy. Using the optimization module within the CNPC’s resource planning information platform UPLAN, they ranked these plays by considering three dimensions—risk, attractiveness, and economic viability. The top 15 plays are listed in Table 1. Among these, the Marine Carbonate Rocks domain contains seven plays, demonstrating a significant numerical advantage and representing a critical future exploration target. The Sichuan Basin hosts four plays within the Marine Carbonate Rocks domain, all of which are highly ranked, making it a key area for achieving theoretical innovations and breakthroughs in oil and gas resource exploration.
The Sichuan Basin demonstrates robust exploration potential, evident in both its substantial oil and gas reserves and promising future exploration plays, making it a practical domain for achieving the next trillion-scale reserves. The overall reservoir-forming conditions of deep to ultra-deep oil and gas reservoirs in the western Sichuan region are well understood. In the northwestern part of the basin, ultra-deep trillion-scale oil and gas fields at depths of 6000–8000 m have been discovered in the Sinian Dengying Formation (Z2dy). Exploration breakthroughs have also been made in the Cambrian Canglangpu (∈1c) and Longwangmiao formations (∈1l). The ultra-deep oil and gas reservoirs of the Lower Permian are mainly distributed in western Sichuan, primarily within the Qixia (P2q) and Maokou (P2m) formations, with resources exceeding one trillion cubic meters. The Changxing Formation (P3c), mainly distributed in western and northern Sichuan, serves as a favorable reservoir from the Late Permian, with a resource potential of 700 billion cubic meters. Large gas fields such as Longgang and Yuanba have been discovered on the western side of the Kaijiang–Liangping Paleo-Trough, with confirmed reserves reaching 300 billion cubic meters. The specific favorable areas and resource potentials for each reservoir are detailed in Table 2.

3.3. Development of Source Rocks in the Sichuan Basin

The Sichuan Basin has abundant ultra-deep oil and gas resources, largely due to the extensive distribution and substantial thickness of marine source rocks, coupled with excellent source–reservoir configurations. In the northwestern part of the basin, the ultra-deep strata develop eight sets of source rocks: the Lower Sinian Doushantuo (Z1ds) Formation, the Upper Sinian third member of the Dengying Formation (Z2dy3), the Lower Cambrian Qiongzhusi Formation (∈1q), the Lower Silurian Longmaxi Formation (S1l), the Middle Devonian (D2), the Middle Permian Maokou Formation (P2m), and the Upper Permian Longtan (P3l), Wujiaping (P3w), and Dalong (P3d) Formations [18]. These represent numerous high-quality source rock intervals. The areal extent of mudstone and shale with Total Organic Carbon (TOC) content exceeding 1.0% reaches 10–16 × 104 km2. The distribution of these thick source rocks is controlled by paleo-rift troughs and their subsequent infilling and leveling patterns. Within the Deyang–Anyue paleo-rift zone, the cumulative thickness of the Maidiping (∈1m) and Qiongzhusi Formations source rocks reaches 340–600 m. Although source rocks within platform facies are generally thinner, the Doushantuo, Qiongzhusi, and Upper Permian source rocks are widely distributed across the Sichuan Basin, serving as the major source rocks that form the foundation for the ultra-deep reservoirs in the region [5] (Table 3).

4. New Insights into Exploration in the Central–Northern Sichuan Basin

Ultra-deep carbonate exploration faces three key challenges: (1) the effectiveness and scale of hydrocarbon generation in source rocks, (2) the effectiveness and scale of ancient carbonate reservoirs, and (3) the preservation and scale of hydrocarbon accumulations after multi-cycle tectonic evolution. The marine carbonate rocks in the Sichuan Basin are characterized by prolonged development, multiple stratigraphic intervals, great depositional thickness, and deep burial [29]. Taking the marine carbonate rocks of the Sinian Dengying Formation in the Sichuan Basin as an example, the period from the Cambrian to the end of the Early Triassic constituted a phase of slow burial, resulting in the descent of the top boundary of the Dengying Formation by varying depths of 1–5 km. From the Late Middle Triassic onward, following the Yanshanian and Himalayan tectonic movements, the top boundary gradually reached depths of 6–8 km below the surface. Driven by tectonic adjustments, the ultra-deep marine carbonate strata underwent a significant high-temperature and high-pressure evolution process [27]. Furthermore, the scale and quality of ultra-deep carbonate reservoirs are collectively controlled by meteoric freshwater dissolution, porosity preservation during the shallow-burial stage, as well as the dissolution and cementation effects of hydrothermal fluids associated with tectonic activities under deep-burial conditions [30,31]. Within the basin, numerous exploration intervals are vertically stratified, primarily controlled by sedimentary facies, with secondary influences from karstification and fault-related modifications [32], demonstrating significant exploration potential [33]. High-quality source rocks are widely distributed near Sinian–Lower Paleozoic reservoirs. Excellent source–reservoir configurations and stable deep geological environments further ensure the large-scale formation of ultra-deep gas accumulations.

4.1. Widespread Distribution of Multi-Layered Ultra-Deep Source Rocks with Superior Hydrocarbon Generation Conditions

Marine source rocks in the Sichuan Basin are extensively distributed, with their deposition controlled by the structural characteristics of depocenters generated through rifting and associated tectonic processes [34]. In the ultra-deep strata of northwestern Sichuan, eight sets of source rocks have been identified: the Lower Sinian Doushantuo Formation, Upper Sinian Deng-3 Member, Lower Cambrian Qiongzhusi Formation [18], Lower Silurian Longmaxi Formation, Middle Devonian, Middle Permian Maokou Formation, and Upper Permian Longtan, Wujiaping, and Dalong Formations. Among these, organic-rich mudstones and shales (TOC > 1.0%) cover an area of 10–16 × 104 km2. Thick source rocks are primarily distributed within rift troughs and infill sequences, such as the 340–600 m thick Maidiping and Qiongzhusi source rocks in the Deyang–Anyue Rift. Although platformal source rocks are thinner, the Doushantuo, Qiongzhusi, and Upper Permian source rocks are widely developed across the basin, serving as the primary hydrocarbon contributors and forming the basis for ultra-deep reservoirs [5] (Table 1).
Two sets of Sinian source rocks—the Doushantuo Formation and Deng-3 Member—are in direct contact with the reservoir units of the Deng-2(Z2dy2) and Deng-4(Z2dy4) Members, ensuring excellent source–reservoir connectivity (Figure 3). The Doushantuo source rocks, as the first sedimentary cap overlying the Dengying reservoirs, directly supply hydrocarbons to the overlying high-quality Deng-2 platform margin reservoirs. Laterally, the Doushantuo source rocks are mainly buried below 8000 m, concentrated in the Deyang–Anyue Rift Trough in northern and eastern Sichuan (Figure 4a). Following the Tongwan Movement II regression, a regional transgression during Deng-3 deposition led to dark mudstone and clastic-dominated sedimentation. The Deng-3 source rocks are primarily distributed in the central–northern part of the Deyang–Anyue Rift Trough, covering >3 × 104 km2 [35], with TOC contents of 0.50–4.73% (avg. 0.87%), classifying them as medium-quality source rocks. Although their gas generation intensity (2 × 108–12 × 108 m3/km2) [36] is moderate, their direct contact with the Deng-2 and Deng-4 reservoirs ensures efficient hydrocarbon migration and contributes significantly to the gas accumulation.
The Cambrian Qiongzhusi Formation source rock is the most widely distributed and highest hydrocarbon-generating dark shale source rock in the ultra-deep strata of the Sichuan Basin. These source rocks are generally buried below 6000 m, with depths exceeding 8000 m in northwestern and eastern Sichuan. The distribution of the source rocks is controlled by the Deyang–Anyue rift trough (Figure 4b), with thickness and TOC content significantly better in the interior of the rift trough than in the exterior, and better in the northern part of the trough than in the southern part [1]. In the northwestern Sichuan region, the Qiongzhusi Formation has an average TOC content of 1.87% and a thickness of 300–700 m (Table 3), exhibiting extremely high hydrocarbon generation potential, with gas generation intensity reaching 20 × 108–200 × 108 m3/km2, making it one of the highest quality source rocks in the entire Sichuan Basin.
During the depositional period of the Upper Ordovician Wufeng Formation to the Silurian Longmaxi Formation, rapid sea level rise resulted in a deep-water shelf depositional environment in the basin, forming a set of organic-rich black shale deposits [37]. Due to the inherited activity of the Central Sichuan Paleo-Uplift, the source rocks of the Silurian Longmaxi Formation were eroded within the paleo-uplift range. Source rocks are distributed throughout the remaining area of the basin, with TOC content greater than 2% and thickness ranging from 0 to 200 m (Table 3). In the eastern and northern Sichuan areas, the burial depth exceeds 6000 m (Figure 5a)
During the Late Permian, under the influence of the Dongwu Movement, the paleogeographic pattern featured high topography in the southwest and low topography in the northeast, transitioning from land to marine environments from southwest to northeast [38]. The Upper Permian Longtan Formation argillaceous source rocks deposited during this period have great thickness, high organic matter abundance, and wide distribution in the basin (Figure 5b), serving as the main source rocks for the Permian system [39]. Vertically, faults connect the Cambrian-Permian reservoirs, forming excellent migration pathways (Figure 3). Large and medium-sized gas fields such as Longgang, Yuanba, and Shuangtan in the northwestern Sichuan region have exhibited natural gas derived from Permian source rocks.
According to conventional geological theory, as burial depth increases, source rocks gradually enter the peak hydrocarbon generation stage due to rising formation temperature, thus implying a minimum depth requirement for effective petroleum exploration. However, continuous breakthroughs in ultra-deep exploration have repeatedly surpassed previous depth limits for commercial oil discoveries [2]. Due to the unique geothermal environment in the Sichuan Basin, the hydrocarbon generation potential of ultra-deep source rocks has not been strongly affected by excessive burial depth or old geological age. The geothermal gradient in the Sichuan Basin ranges from 17.7–33.3 °C/km, with terrestrial heat flow values around 53.2 mW/m2, placing it in the transitional zone between “cold basins” and “hot basins” [40]. This characteristic significantly increases the lower limit of hydrocarbon generation depth for source rocks, forming the basis for large-scale oil and gas preservation at depths of up to 10,000 m. The eastern, northern, and western Sichuan Basin exhibit the lowest geothermal gradients, with temperatures at 10,000-m depths generally below 220 °C—the lowest in the basin. For Type I/II organic matter or kerogen, the lower limit of thermal degradation (primary cracking) for gas generation can extend to Ro = 3.5%, corresponding to a gas generation depth of up to 12,500 m. Additionally, the cracking of residual hydrocarbons within source rocks and liquid hydrocarbons outside source rocks serves as an important pathway for gas generation in high-overmature shale gas and deep conventional gas reservoirs [7], indicating substantial hydrocarbon generation potential.
Taking the Cambrian Qiongzhusi Formation source rock—the main hydrocarbon source for the Sinian Dengying Formation gas reservoir in the Anyue Gas Field—as an example, it primarily generated oil before the Late Triassic. From the Late Triassic to Cretaceous, organic matter entered a gas-dominated generation stage. By the end of the Cretaceous, formation temperatures reached their peak, marking a critical period for natural gas accumulation. A total of four Hydrocarbon charging event have been identified. The relatively late formation of natural gas, coupled with its alignment with multiple tectonic events and accumulation factors, ultimately determines the effectiveness and scale of ultra-deep hydrocarbon reservoirs [41].

4.2. Large-Scale and Inherited Stacked Development of Multiple Sinian–Lower Paleozoic Mound–Shoal Complexes in Ultra-Deep Strata

The Sinian–Lower Paleozoic platform margin mound–shoal complexes are extensively developed in the Sichuan Basin. Multiple stages of high-quality mound–shoal facies reservoirs are vertically superimposed, forming several favorable zones such as the slope belt of the paleo-uplift in the northwestern Sichuan Basin, permian platform margin belt in sichuan basin, synclinal area in the eastern–southern sichuan basin, and reef-bank complex in the northern rift depression of the Sichuan basin (Table 1). This provides advantageous conditions for ultra-deep oil and gas accumulation [42].
From the developmental characteristics of each stage of mound–shoal complexes, the Sinian–Lower Paleozoic platform margin mound–shoal complexes are extensively developed in the Sichuan Basin, forming multiple large-scale reservoir intervals. In the northwestern Sichuan region, thick mound–shoal complexes of the Deng-2 and Deng-4 members are distributed along the eastern margin of the Deyang–Anyue Rift Trough. The platform margin facies belt of the Dengying Formation extends northwestward into the open marine environment, with the platform margin zone gradually increasing in width, thickness and areal extent compared to the central Sichuan area (Figure 6). During the early Cambrian Canglangpu Formation deposition, uplift occurred in the western part of the basin forming paleo-land, while the rift trough deepened with deep-water shelf facies developing in its interior. Oolitic dolomite shoals of shallow-water shelf facies were deposited along its eastern margin, and these shallow-water shelf mound–shoal deposits continued to develop towards the eastern margin of the basin. In the Middle Cambrian, the underwater paleo-uplifts developed in central–western Sichuan, with grain shoal facies dolomites of the Longwangmiao Formation widely distributed around the high parts of paleo-uplifts [43]. During Devonian–Carboniferous deposition, the northwestern Sichuan area developed a land-attached rimmed platform with bioclastic shoal facies dolomites distributed in belts, forming conditions for large-scale reservoir development. In the Permian, multiple phases of rift troughs developed in the Sichuan Basin, with four superimposed platform margin belts (Qixia–Maokou–Wujiaping–Changxing) developing in northwestern Sichuan (Figure 6).
In terms of reservoir characteristics, core samples reveal the concurrent development of closely spaced honeycomb-like micropores and large dissolution pores/vugs, with the diameters of dissolution caves reaching 2–3 cm and exhibiting an irregular distribution (Figure 7). The ultra-deep reservoirs in the Sichuan Basin are fracture–cavity types. They formed when the primary pores of early microbial frameworks in mound–shoal facies were altered by meteoric freshwater, deep hydrothermal fluids, and acidic fluids [44]. From the Sinian to Middle Triassic, marine carbonate rocks dominate, with most dolomites formed through dolomitization of limestone. Dolomitization enhances porosity preservation during burial, preserving primary pores, but also makes it more prone to fracturing. Uncemented fractures provide excellent fluid migration channels that connect isolated primary pores, forming highly efficient transport systems that significantly improve permeability in ultra-deep environments. Within platform and platform margin facies, reservoirs mainly consist of microbial mounds/shoals composed of algal dolomite, inter-shoal depressions of granular/crystalline dolomite, and shallow shoals. Among these, primary pores in platform margin facies formed under high hydrodynamic conditions show the best quality. In addition to inherited primary pores, the shallow water depth and large sea-level fluctuations in platform and platform margin facies led to syndepositional–quasi-syngenetic dissolution pores formed during intermittent exposure. Subsequent modifications by tectonic movements (Tongwan, Xingkai, and Caledonian) created karst weathering crust reservoirs through superimposed post-depositional exposure. These combine with dissolution pores from burial-stage hydrothermal/acidic fluids and tectonic fractures from deep geological movements to form high-quality fracture–cavity reservoirs [5]. Although primary pores are rarely preserved intact, they provide initial migration pathways for corrosive fluids. The secondary pores—mainly including intergranular dissolution pores expanded and reformed from primary pores, and newly formed intragranular dissolution pores—are the most dominant pore types in the northern Sichuan region [6]. The secondary porosity created through these dissolution enhancement processes on primary pores constitutes the dominant reservoir space in the region.
There are distinct differences in reservoir characteristics between the northwestern and central Sichuan regions. In central Sichuan, reservoirs are jointly controlled by sedimentary facies distribution and karstification processes. Reservoir development is primarily governed by mound–shoal complexes, with superimposed karst modification creating enlarged dissolution pores that now constitute the main reservoir spaces (Figure 8a,b) [7]. In contrast, northwestern Sichuan shows stronger influence from syndepositional to quasi-syndepositional karstification in addition to late-stage weathering crust karst effects. During this early stage, the bedrock had lower maturity, having experienced only shallow burial or relatively short burial duration. This early-stage condition allowed the formation of high-quality fluid migration channels within the bedrock itself. Karst fluids dissolved the internal bedrock matrix, creating three-dimensional network-like dissolution spaces that ultimately developed into interconnected dissolution networks (Figure 8c–f).

4.3. Stable Geological Environment and Well-Developed Structural-Lithologic Traps in Northwestern Sichuan’s Ultra-Deep Strata Create Superior Accumulation Conditions

The northwestern Sichuan Basin has undergone multiple tectonic events including the Yangtze, Caledonian, Hercynian, Indosinian, Yanshanian, and Himalayan cycles. Before the Himalayan movement, the basement remained tectonically stable for prolonged periods, with the basin’s structural mechanisms controlled by peripheral orogenic belts rather than deep lithosphere and mantle processes, representing a unique superimposed basin evolution model [45]. This distinctive evolutionary pattern provided essential conditions for preserving ultra-deep hydrocarbon reservoirs. During the Himalayan movement, the Longmen Shan orogenic belt remained tectonically active, forming three structural zones in northwestern Sichuan from west to east: the nappe orogenic belt, nappe front, and nappe uplift zone [46,47]. Deep major faults in the piedmont nappe zone led to the severe dispersion of paleo-reservoirs, hindering hydrocarbon accumulation. In contrast, ultra-deep reservoirs in northwestern Sichuan were primarily found in the nappe front, nappe uplift zone, and slope environments, which are more distant from the orogenic belt. These areas maintained overall stable deep structural conditions (Figure 9) that persist to this day, establishing the foundation for ultra-deep hydrocarbon accumulation.
Applsci 15 11380 g008
Figure 8. Comparison of Reservoir Microcharacteristics in Central–Northern Sichuan Basin (a) Well GS16, 5463.93 m, algal framework dolomite with saddle dolomite cement in interframework dissolution pores; (b) Well GS16, 5464.69 m, micritic dolomite with saddle dolomite cement in intragranular dissolution pores; (c) Well W1, 219.5 m, micritic dolomite with bitumen-filled intragranular dissolution pores; (d) Well W1, 298.5 m, micritic dolomite with syndepositional to penecontemporaneous dissolution pores; (e) Well W1, 229.5 m, algal-framework dolomite with bitumen-filled interframework dissolution pores; (f) Well W1, 342 m, micritic dolomite with syndepositional to penecontemporaneous dissolution pores.
Figure 8. Comparison of Reservoir Microcharacteristics in Central–Northern Sichuan Basin (a) Well GS16, 5463.93 m, algal framework dolomite with saddle dolomite cement in interframework dissolution pores; (b) Well GS16, 5464.69 m, micritic dolomite with saddle dolomite cement in intragranular dissolution pores; (c) Well W1, 219.5 m, micritic dolomite with bitumen-filled intragranular dissolution pores; (d) Well W1, 298.5 m, micritic dolomite with syndepositional to penecontemporaneous dissolution pores; (e) Well W1, 229.5 m, algal-framework dolomite with bitumen-filled interframework dissolution pores; (f) Well W1, 342 m, micritic dolomite with syndepositional to penecontemporaneous dissolution pores.
Applsci 15 11380 g008
Applsci 15 11380 g009
Figure 9. Sichuan Basin Structural Characteristics and Hydrocarbon Reservoir Distribution Cross-section.
Figure 9. Sichuan Basin Structural Characteristics and Hydrocarbon Reservoir Distribution Cross-section.
Applsci 15 11380 g009
The discovery of the Shuangyushi area’s large, integrated ultra-deep gas field in the Qixia Formation confirms this conclusion. Under strong NW-directed compression during the early Indosinian movement, early extensional normal faults in Shuangyushi reversed into back-thrust faults, forming a series of anticlinal structures that constitute the main trap framework [48]. From Middle–Late Triassic to present, under continuous NW compression, pre-existing structural traps continued developing, with faulting ultimately ceasing in the Late Triassic. This formed composite structural-lithologic traps dominated by large thrust fault structures with subsidiary lithologic traps [36]. During the Himalayan movement, the Shuangyushi area’s position in the weakly deformed nappe front allowed faults to connect with underlying source rocks without compromising trap sealing integrity. This enabled stable preservation of early hydrocarbon accumulations to the present day, which is key to the large-scale accumulation of Qixia Formation gas in the Shuangyushi structure [49].
In the Sichuan Basin, lithologic traps are predominantly developed in the Sinian to Permian strata. Within the carbonate platform depositional environment, high-energy mound–beach complexes typically occur as isolated bodies. Dense Crystalline Dolostone deposited between these mound–beach complexes provide effective lateral sealing for reservoirs within the mounds. This geological phenomenon is widely observed in both platform and platform margin facies belts in the northern Sichuan region [30] (Figure 10). Additionally, structural traps formed by faults play a crucial sealing role in shoal reservoirs. During the deposition of the Dengying Formation, the Tongwan Movement generated numerous normal faults. Mound–shoal facies sediments developed along the uplifted sections of these faults, while the downthrown blocks accumulated Cambrian Qiongzhusi Formation source rocks, creating lateral contact between source and reservoir rocks. This configuration establishes lithologic barriers while also connecting source and reservoir strata [50]. Direct lithologic caprocks are vital for the formation of gas reservoirs. Additionally, regional caprocks that form stratigraphic traps are also critical for large-scale gas accumulation. The Central Sichuan Paleo-Uplift hosts two major regional shale caprocks: the Cambrian Qiongzhusi Formation and the Permian Longtan Formation. The Qiongzhusi Formation is 50–400 m thick, with a breakthrough pressure of 15–50 MPa, while the Longtan Formation is 60–160 m thick, with a breakthrough pressure of 15–30 MPa. Both provided effective sealing capacity during peak hydrocarbon generation [51].

5. Analysis and Prospects of Ultra-Deep Natural Gas Exploration Potential in Sichuan Basin

The evolution of Sichuan Basin has been primarily controlled by the thrust nappe belts of Longmen Mountain and Daba Mountain along its western and northeastern margins. The basin’s unique superimposed pattern has maintained long-term stability in its ultra-deep strata that persists to this day. The formation and inherited development of Deyang–Anyue Rift Trough and Central Sichuan Paleo-Uplift have significantly governed the filling of source rocks and the formation of Sinian–Lower Paleozoic mound–shoal facies reservoirs, resulting in direct contact between reservoirs and source rocks. This proximal reservoir–source configuration represents one of the critical factors for ultra-deep hydrocarbon accumulation [36].
According to CNPC’s statistical data, the favorable zones of the mound-beach facies in the Sinian Dengying Formation are primarily distributed on the eastern side of the Deyang–Anyue Rift Trough, with a burial depth ranging from 6000 to 8000 m (Figure 11a). In the Penglai area, 41 wells have confirmed reserves of 796.4 billion cubic meters. The reservoir formation conditions in the Northwestern Sichuan Region are more favorable, with a resource potential of 8.2 trillion cubic meters (Table 2). During the Cambrian, two phases of grain beach facies reservoirs developed in the Canglangpu and Longwangmiao formations of the northern Sichuan Basin, east of the Deyang–Anyue Intra-Cratonic Rift Trough (Figure 11b). In the northwestern Sichuan region, 15 wells have currently penetrated the Longwangmiao Formation. Among these, the Dongba 1 Well achieved a gas production rate of 200,000 cubic meters per day. The overall resource potential for this area is estimated at 0.4 trillion cubic meters (Table 2). The Canglangpu Formation has been penetrated by 15 wells. Among these, the Jiaotan 1 Well achieved a gas flow rate of 516,200 cubic meters per day. The estimated resource potential for this formation is 1.5 trillion cubic meters (Table 2). Favorable Devonian–Carboniferous beach facies reservoirs are primarily distributed along the western margin of the basin (Figure 12a) [52]. A total of 14 wells have penetrated the Guanwushan and Zongchanggou formations. Among these, the Shuangtan 3 Well achieved a test production rate of 116,000 cubic meters per day. The overall resource potential is estimated at approximately 1 trillion cubic meters (Table 2). The Lower Permian Qixia Formation is mainly distributed along the western margin of the basin (Figure 12b). In the northwestern Sichuan region, its burial depth generally exceeds 6000 m, with a resource potential of 0.78 trillion cubic meters (Table 2). The Lower Permian Maokou Formation primarily exhibits a NW-SE distribution trend across the basin. In northern Sichuan, it is buried below 6000 m, classifying it as a deep to ultra-deep reservoir, with a resource potential of 0.8 trillion cubic meters (Table 2). The Middle-Upper Permian reef-beach facies reservoirs are predominantly found in western and northern Sichuan. Discoveries include gas reservoirs in the Changxing and Feixianguan formations of the Longgang and Yuanba areas. The favorable reef-beach zone north of the Pengxi–Wusheng intra-platform depression covers an area of 1000 km2. This zone is sourced by dual hydrocarbon sources from the Cambrian and Silurian, with strike-slip faults facilitating migration between source and reservoir. Within this area, the Pengshen 2 Well encountered thick gas-bearing zones in the Changxing Formation. The overall resource potential for this play is estimated at 0.7 trillion cubic meters (Table 2).
The environments for hydrocarbon generation, reservoir formation, and accumulation in deep to ultra-deep exploration are significantly different from those in medium and shallow layers. Achieving breakthroughs in oil and gas exploration requires both theoretical innovation and technological advancement. Implementing the ten-thousand-meter drilling program in the Sichuan Basin is a crucial pathway for discovering large-scale strategic replacement resources, innovating ultra-deep petroleum geological theories, and enhancing engineering technological capabilities. It represents a major initiative to implement the national and corporate deep-earth strategy and ensure energy security.

6. Conclusions

As a typical complex cratonic basin, the Sichuan Basin exhibits a tectonic evolution model that, while increasing the challenges of ultra-deep exploration, also provides a favorable environment for hydrocarbon preservation due to its unique geological conditions: (1) multiple sets of hydrocarbon source rocks, such as those in the Doushantuo, Qiongzhusi, Longmaxi, and Longtan formations, have a great maximum burial depth limit for hydrocarbon generation and are widely distributed at depths exceeding 6000 m, creating an advantage of “near-source hydrocarbon supply”, and (2) in the northwestern Sichuan region, multiple high-quality reservoir formations are vertically stacked and developed, including the Sinian Dengying Formation platform margin zone, Cambrian grain shoal facies, Devonian–Carboniferous reef–shoal facies, and Permian high-energy platform margin zones.
Current discoveries of ultra-deep oil and gas in the Sichuan Basin continuously reveal its resource potential, yet the following problems and challenges remain: (1) The reservoirs in the Sinian–Lower Paleozoic are highly heterogeneous, and there is a lack of effective means for quantitatively evaluating the extent and intensity of paleo-oil dismigration dispersal caused by tectonic activity. (2) The strong heterogeneity of Sinian–Lower Paleozoic reservoirs and the complexity of resource distribution make target selection difficult.
In response to the above challenges, promoting the collaborative innovation of deep petroleum geology theory and engineering technology is the essential path for future ultra-deep oil and gas exploration: (1) intensify research on the reservoir formation mechanisms of ultra-deep carbonate rocks to establish reservoir prediction models that couple karst and tectonic factors; (2) investigate the lower limit of hydrocarbon generation in ancient source rocks to refine the theory of ultra-deep accumulation; and (3) enhance the quality of deep seismic interpretation, implement measures to increase drilling speed and efficiency in deep layers, and develop logging technologies for high-temperature and high-pressure deep environments to support the rapid development of deep and ultra-deep oil and gas exploration.

Author Contributions

Conceptualization, Z.Z. and G.Z.; methodology, Z.Z.; validation, Z.Y., Q.L. and H.C.; formal analysis, Z.Y., Q.L. and H.C.; investigation, Z.Z. and G.Z.; resources, Z.Z. and G.Z.; data curation, Z.Y., Q.L. and H.C.; writing—original draft preparation, Z.Y. and Q.L.; writing—review and editing, Z.Y. and B.D.; visualization, Z.Y. and B.D.; supervision, Z.Z. and G.Z.; project administration, Z.Y., Q.L. and H.C.; funding acquisition, Z.Z. and G.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by China National Petroleum Corporation (CNPC) major science and technology projects (2023ZZ16YJ01), and National Natural Science Foundation of China (U2344209), and National Natural Science Foundation of China (No. 42306083), and Central Universities Basic Research Operating Expenses Project (No. 3-7-9-2024-06).

Data Availability Statement

Data is contained within the article.

Conflicts of Interest

Author Gang Zhou was employed by the company Petro China Southwest Oil & Gasfield Company Exploration and Development Research Institute. Author Zili Zhang was employed by the company Petro China Southwest Oil & Gasfield Company Exploration and Development Research Institute. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from China National Petroleum Corporation, National Natural Science Foundation of China and Central Universities Basic Research Operating Expenses Project. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.

References

  1. Huang, S.P.; Jiang, H.; Wang, T.S.; Wen, L.; Guan, S.W.; Zeng, F.Y.; Zhu, G.Y.; Tian, X.W.; Zhang, T.Y. Accumulation conditions and favorable exploration zones for natural gas in 8000 meters marine ultra-deep strata in the Sichuan basin. Acta Geol. Sin. 2023, 97, 1544–1560. [Google Scholar] [CrossRef]
  2. Chen, Z.; Li, W.; Wang, L.; Lei, Y.; Yang, G.; Zhang, B.; Yin, H.; Yuan, B. Structural geology and favorable exploration prospect belts in northwestern Sichuan Basin, SW China. Pet. Explor. Dev. 2019, 46, 413–425. (In Chinese) [Google Scholar] [CrossRef]
  3. Yu, H.; Juan, H.; Wen, Z. Distribution features and exploration potential of oil and gas in a deepwater area of the Gulf of Mexico Basin. Pet. Geol. Exp. 2015, 37, 473–478. [Google Scholar] [CrossRef]
  4. Zou, C.; Zhai, G.; Zhang, G.; Wang, H.; Zhang, G.; Li, J.; Wang, Z.; Wen, Z.; Ma, F.; Liang, Y.; et al. Formation, distribution, potential and prediction of global conventional and unconventional hydrocarbon resources. Pet. Explor. Dev. 2015, 42, 14–28. (In Chinese) [Google Scholar] [CrossRef]
  5. He, D.; Jia, C.; Zhao, W.; Xu, F.; Luo, X.; Liu, W.; Tang, Y.; Gao, S.; Zheng, X.; Li, D.; et al. Research progress and key issues of ultra-deep oil and gas exploration in China. Pet. Explor. Dev. 2023, 50, 1162–1172. [Google Scholar] [CrossRef]
  6. Jia, C. Key scientific and technological problems of petroleum exploration and development in deep and ultra-deep formation. J. China Univ. Pet. 2023, 47, 1–12. [Google Scholar] [CrossRef]
  7. Jia, C.; Zhang, S. The formation of marine ultra-deep petroleum in China. Acta Geol. Sin. 2023, 97, 2775–2801. [Google Scholar] [CrossRef]
  8. Dai, J.; Ni, Y.; Qin, S.; Huang, S.; Peng, W.; Han, W. Geochemical characteristics of ultra-deep natural gas in the Sichuan Basin, SW China. Pet. Explor. Dev. 2018, 45, 619–628. [Google Scholar] [CrossRef]
  9. He, D.; Li, D.; Zhang, G.; Zhao, L.; Fan, C.; Lu, Q.; Wen, Z. The formation and evolution of multi cycle superimposed basins in Sichuan Province. Geol. Sci. 2011, 46, 589–606. [Google Scholar] [CrossRef]
  10. Duan, J.; Mei, Q.; Li, B.; Liang, Z. The tectonic sedimentary evolution process of the Early Cambrian in the Sichuan Basin. Earth Sci. 2019, 44, 738–755. [Google Scholar] [CrossRef]
  11. Ma, Y.; He, Z.; Zhao, P.; Zhu, H.; Han, J.; You, D.; Zhang, J. New progress in the formation mechanism of deep-ultra-deep carbonate reservoirs. Acta Pet. Sin. 2019, 40, 1415–1425. (In Chinese) [Google Scholar]
  12. Guo, X.; Hu, D.; Huang, R.; Wei, Z.; Duan, J.; Wei, X.; Fan, X.; Miao, Z. Deep and ultra-deep natural gas exploration in the Sichuan Basin: Progress and prospect. Nat. Gas Ind. 2020, 7, 419–432. [Google Scholar] [CrossRef]
  13. Ren, J. Composition, structure, evolution and dynamics of Chinese mainland. Acta Geol. Sin. 1994, Z2, 5–13. (In Chinese) [Google Scholar]
  14. Shi, S.; Wang, Y.; Chen, C.; Liu, J.; Peng, P. Influence of tectonic evolution processes on burial, thermal maturation and gas generation histories of the Wufeng-Longmaxi shale in the Sichuan Basin and adjacent areas. Int. J. Coal Geol. 2024, 295, 104642. [Google Scholar] [CrossRef]
  15. Wei, G.; Li, J.; She, Y.; Zhang, G.; Shao, L.; Yang, G.; Guan, H.; Yang, S.; Lin, J.; Wang, R. Distribution law of large gas fields in China and the next exploration direction. Nat. Gas Ind. 2018, 38, 12–25. [Google Scholar] [CrossRef]
  16. Zhang, Z.; Zhao, L.; Zhang, D.; Li, Q.; Chen, H.; Wen, L.; Zhang, B.; Zhou, G.; Zhong, Y.; Wenzheng, L. Diagenetic evolution and cementation mechanism in deep Carbonate reservoirs: A case study of Dengying Fm. 2 in Penglai, Sichuan Basin, China. Mar. Pet. Geol. 2024, 170, 107084. [Google Scholar] [CrossRef]
  17. Shi, S.; Yang, W.; Zhou, G.; Jiang, H.; Meng, H.; Wu, S.; Zhang, Y.; Lu, W.; Bai, Z. Impact of Tethyan domain evolution on the formation of petroleum systems in the Sichuan super basin, SW China. Pet. Explor. Dev. 2024, 51, 1183–1201. [Google Scholar] [CrossRef]
  18. Yang, W.; Wei, G.; Wu, S.; Xie, W.; Jin, H.; Zeng, F.; Hao, C.; Bai, Z.; Su, Y.; Li, R. Regional unconformities and their controls on hydrocarbon accumulation in Sichuan Basin, SW China. Pet. Explor. Dev. 2023, 50, 573–587. [Google Scholar] [CrossRef]
  19. Chen, H.; Wang, S.; Mansour, A.; Qin, Q.; Ahmed, M.S.; Cen, Y.; Liang, F.; He, Y.; Fan, Y.; Gentzis, T. Key Characteristics and Controlling Factors of the Gas Reservoir in the Fourth Member of the Ediacaran Dengying Formation in the Penglai Gas Field, Sichuan Basin. Minerals 2025, 15, 98. [Google Scholar] [CrossRef]
  20. Wang, Z.; Jiang, H.; Wang, T.; Lu, W.; Gu, Z.; Xu, A.; Yang, Y.; Xu, Z. Paleo-geomorphology formed during Tongwan tectonization in Sichuan Basin and its significance for hydrocarbon accumulation. Pet. Explor. Dev. 2014, 41, 338–345. [Google Scholar] [CrossRef]
  21. Li, H.K. Study on Geological Structure and Superimposed Characteristics of Sichuan Basin. Ph.D. Thesis, Chengdu University of Technology, Chengdu, China, 2020. [Google Scholar] [CrossRef]
  22. Ma, K.; Wen, L.; Zhang, B.; Li, Y.; Zhong, J.; Wang, Y.; Peng, H.; Zhang, X.; Yan, W.; Ding, Y.; et al. Segmented evolution of Deyang-Anyue erosion rift trough in Sichuan Basin and its significance for oil and gas exploration, SW China. Pet. Explor. Dev. 2022, 49, 274–284. [Google Scholar] [CrossRef]
  23. Luo, B.; Yang, Y.; Luo, W.; Wen, L.; Wang, W.; Chen, K. Controlling factors of Dengying Formation reservoirs in the central Sichuan paleo-uplift. Pet. Res. 2017, 2, 54–63. [Google Scholar] [CrossRef]
  24. Yu, Y.; Long, W.; Gang, Z.; Weiyun, Z.; Haitao, L.; Zezhang, S.; Jing, Z.; Jiali, T.; Xingwang, T.; Jiutao, Y.; et al. New fields, new types and resource potentials of hydrocarbon exploration in Sichuan Basin. Acta Pet. Sin. 2023, 44, 2045–2069. [Google Scholar] [CrossRef]
  25. Liu, S.; Yang, Y.; Deng, B.; Zhong, Y.; Wen, L.; Sun, W.; Li, Z.; Jansa, L.; Li, J.; Song, J.; et al. Tectonic evolution of the Sichuan Basin, Southwest China. Earth-Sci. Rev. 2021, 213, 103470. [Google Scholar] [CrossRef]
  26. Xie, W.; Wen, L.; Wang, Z.; Hao, Y.; Xin, Y.; Wu, S.; Li, W.; Yao, Q.; Ma, S.; Chen, Y. Permian-Middle Triassic marine unconventional resource types and favorable exploration directions in Sichuan Basin. Nat. Gas Geosci. 2024, 35, 961–971. [Google Scholar] [CrossRef]
  27. Deng, K.L. Formation and Evolution of Sichuan Basin and Domains for Oil and Gas Exploration. Nat. Gas Ind. 1992, 12, 7–12. (In Chinese) [Google Scholar]
  28. Huang, F.; Wang, S.; Li, M.; Ouyang, J.; Liu, C.; Liu, H.; Zeng, F.; Fan, J.; Jia, P. Progress and implications of deep and ultra-deep oil and gas exploration in PetroChina. Nat. Gas Ind. 2024, 44, 86–96. [Google Scholar] [CrossRef]
  29. Hu, Y.; Peng, X.; Li, Q.; Li, L.; Hu, D. Progress and development direction of technologies for deep marine carbonate gas reservoirs in the Sichuan Basin. Nat. Gas Ind. B 2020, 7, 149–159. [Google Scholar] [CrossRef]
  30. Zheng, H.; Ma, Y.; Chi, G.; Qing, H.; Liu, B.; Zhang, X.; Shen, Y.; Liu, J.; Wang, Y. Stratigraphic and Structural Control on Hydrothermal Dolomitization in the Middle Permian Carbonates, Southwestern Sichuan Basin (China). Minerals 2019, 9, 32. [Google Scholar] [CrossRef]
  31. Qiao, Z.; Yu, Z.; She, M.; Pan, L.; Zhang, T.; Li, W.; Shen, A. New progress in the genesis of ancient ultra-deep marine carbonate reservoirs in China. Acta Paleogeogr. 2023, 25, 1257–1276. [Google Scholar] [CrossRef]
  32. Zhu, G.; Jiang, H.; Huang, S.; Ma, D.; Zhang, M.; Chen, W.; Guan, S.; Fan, J.; Zeng, F. New Progress in China’s Marine Oil and Gas Accumulation Theory and Prediction of 10,000-meter-deep Super-large Oil and Gas Areas. Acta Pet. Sin. 2025, 46, 816–842. [Google Scholar] [CrossRef]
  33. Wang, Z.; Zhao, Z.; Huang, F.; Shi, Y.; Xu, Y.; Zhang, S. Ultra-deep hydrocarbon accumulation conditions and exploration potential in sedimentary basins of Central-Western China. World Pet. Ind. 2024, 31, 33–48. [Google Scholar] [CrossRef]
  34. Tenger; Liu, W.; Qin, J.; Zheng, L.; Fu, X.; Shen, B.; Lu, L.; Wang, J. Dynamic transformation mechanism for hydrocarbon generation from multiple sources in deep-buried marine carbonates in the northeastern Sichuan Basin: A case study from the Puguang gas field. Acta Petrol. Sin. 2012, 28, 895–904. [Google Scholar]
  35. Du, J.; Wang, Z.; Zou, C.; Xu, C.; Shen, P.; Zhang, B.; Jiang, H.; Huang, S. Discovery of intrrcratonie rift in the Upper Yangtze and its coutrol effect on the formation of Anyue giant gas field. Russ. Geol. Geophys. 2020, 61, 478–494. [Google Scholar] [CrossRef]
  36. Li, J.; Tao, X.; Bai, B.; Huang, S.; Jiang, Q.; Zhao, Z.; Chen, Y.; Ma, D.; Zhang, L.; Li, N.; et al. Geological conditions, reservoir evolution and favorable exploration directions of marine ul-tra-deep oil and gas in China. Pet. Explor. Dev. 2021, 48, 52–79. [Google Scholar] [CrossRef]
  37. Ma, X. Exploration of the Enrichment Law and Scale Effective Development of Shale Gas in the Southern Sichuan Basin. Nat. Gas Ind. 2018, 38, 240–249. [Google Scholar] [CrossRef]
  38. Liang, X.Q.; Zhou, Y.; Jiang, Y.; Wen, S.N.; Fu, J.G.; Wang, C. Difference of sedimentary response to Dongwu Movement: Study on LA-ICPMS U-Pb ages of detrital zircons from Upper Permian Wujiaping or Longtan Formation from the Yangtze and Cathaysia blocks. Acta Petrol. Sin. 2013, 29, 3592–3606. [Google Scholar]
  39. Chen, J.; Li, W.; Ni, Y.; Liang, D.; Deng, C.; Bian, L. Permian source rocks and their natural gas exploration potential in Sichuan Basin (1) Spatial distribution characteristics of source rocks. Nat. Gas Ind. 2018, 38, 1–16. [Google Scholar] [CrossRef]
  40. Xu, M.; Zhu, C.Q.; Tian, Y.T.; Rao, S.; Hu, S.B. Borehole temperature logging and characteristics of subsurface temperature in Sichuan Basin. Chin. J. Geophys. 2011, 54, 1052–1060. (In Chinese) [Google Scholar] [CrossRef]
  41. Yang, Y.; Yang, Y.; Yang, G.; Song, J.; Wen, L.; Deng, C.; Xia, M.; Ran, Q.; Duan, G.; Luo, B.; et al. Gas accumulation conditions and key technologies for exploration & development of Sinian and Cambrian gas reservoirs in Anyue gasfield. Pet. Res. 2018, 3, 221–238. [Google Scholar] [CrossRef]
  42. Ma, X.; Yang, Y.; Wen, L.; Luo, B. Distribution and exploration direction of medium- and large-sized marine carbonate gas fields in Sichuan Basin, SW China. Pet. Explor. Dev. 2019, 46, 1–13. (In Chinese) [Google Scholar] [CrossRef]
  43. Jin, M.; Zeng, W.; Tan, X.; Li, L.; Li, Z.; Luo, B.; Zhang, J.; Liu, J. Characteristics and controlling factors of beach-controlled karst reservoirs in Cambrian Longwangmiao Formation, Moxi-Gaoshiti area, Sichuan Basin, NW China. Pet. Explor. Dev. 2014, 41, 712–723. [Google Scholar] [CrossRef]
  44. Jiang, Y.; Gu, Y.; Zhu, X.; Xu, W.; Xiao, Y.; Li, J. Hydrothermal dolomite reservoir facies in the Sinian Dengying Fm, central Sichuan Basin. Nat. Gas Ind. B 2017, 4, 287–293. [Google Scholar] [CrossRef]
  45. Wei, G.; Yang, W.; Du, J.; Xu, C.; Zou, C.; Xie, W.; Wu, S.; Zeng, F. Tectonic features of Gaoshiti-Moxi paleo-uplift and its controls on the formation of a giant gas field, Sichuan Basin, SW China. Pet. Explor. Dev. 2015, 42, 283–292. [Google Scholar] [CrossRef]
  46. Xiao, D.; Wen, L.; Zhang, Y.; Xie, C.; Tan, X.; Cao, J. Natural gas accumulation in the basin–mountain transition zone, northwestern Sichuan Basin, China. Mar. Pet. Geol. 2021, 133, 105305. [Google Scholar] [CrossRef]
  47. Xiao, D.; Cao, J.; Luo, B.; Zhang, Y.; Xie, C.; Chen, S.; Gao, G.; Tan, X. Mechanism of ultra-deep gas accumulation at thrust fronts in the Longmenshan Mountains, lower Permian Sichuan Basin, China. J. Nat. Gas Sci. Eng. 2020, 83, 103533. [Google Scholar] [CrossRef]
  48. Zheng, C.; Zhang, B.; Li, R.; Yin, H.; Wang, Y.; Hu, X.; Chen, X.; Liu, R.; Zeng, Q.; Sun, Z.; et al. Facies-controlled prediction of dolomite reservoirs in the Middle Permian Qixia Formation in Shuangyushi, northwestern Sichuan Basin. Energy Geosci. 2024, 5, 100230. [Google Scholar] [CrossRef]
  49. Yang, Y.; Jiang, P.; Zhang, B.; Di, X.; Hua, W.; Cheng, L.; Ya, Z.; Xiao, C.; Ran, L.; Ya, L. Formation of ultra-deep integrated giant gas field in Qixia Formation of Shuangyushi structure in the foothill complex structural belt of Longmen mountain. Nat. Gas Ind. 2022, 42, 1–11. [Google Scholar] [CrossRef]
  50. Wei, G.; Xie, Z.; Yang, Y.; Li, J.; Yang, W.; Zhao, L.; Yang, C.; Zhang, L.; Xie, W.; Jiang, H.; et al. Formation conditions of Sinian–Cambrian large lithologic gas reservoirs in the north slope area of central Sichuan Basin, SW China. Pet. Explor. Dev. 2022, 49, 963–976. [Google Scholar] [CrossRef]
  51. Xie, W.; Chen, S.; Gan, H.; Wang, H.; Wang, M.; Vandeginste, V. Preservation conditions and potential evaluation of the Longmaxi shale gas reservoir in the Changning area, southern Sichuan Basin. Geosci. Lett. 2023, 10, 36. [Google Scholar] [CrossRef]
  52. Zhou, G.; Tian, X.; Wen, L.; Zhang, B.; Yang, D.; Yao, J.; Sun, Y.; Xiang, Z.; Zhou, L.; Tang, H. New evidence of Devonian-Carboniferous paleo-depression in the western Sichuan Basin and its implications for oil and gas geology. Nat. Gas Ind. 2023, 43, 1–11. [Google Scholar] [CrossRef]
Applsci 15 11380 g003
Figure 3. Superimposed Cross-section of Source Rocks in Northern Sichuan Region.
Figure 3. Superimposed Cross-section of Source Rocks in Northern Sichuan Region.
Applsci 15 11380 g003
Applsci 15 11380 g004
Figure 4. Thickness of Sinian–Cambrian Source Rocks in Sichuan Basin (a) Doushantuo Formation; (b) Qiongzhusi Formation.
Figure 4. Thickness of Sinian–Cambrian Source Rocks in Sichuan Basin (a) Doushantuo Formation; (b) Qiongzhusi Formation.
Applsci 15 11380 g004
Applsci 15 11380 g005
Figure 5. Thickness of Sinian–Cambrian Source Rocks in Sichuan Basin (a) Longmaxi Formation; (b) Upper Permian.
Figure 5. Thickness of Sinian–Cambrian Source Rocks in Sichuan Basin (a) Longmaxi Formation; (b) Upper Permian.
Applsci 15 11380 g005
Applsci 15 11380 g006
Figure 6. Composite Section of Ultra-Deep Reservoirs in the Northwestern Sichuan Basin.
Figure 6. Composite Section of Ultra-Deep Reservoirs in the Northwestern Sichuan Basin.
Applsci 15 11380 g006
Applsci 15 11380 g007
Figure 7. Core Photographs of Ultra-Deep Reservoirs in Sichuan Basin. (a) Well PT101, Sinian Deng-2 Member, Central Sichuan Basin, thrombolite dolomite with well-developed dissolution vugs; (b) Well PS6, Sinian Deng-4 Member, Central Sichuan Basin, thrombolite dolomite with needle-like dissolution pores; (c) Well PS11, Cambrian Longwangmiao Formation, Central Sichuan Basin, grainstone dolomite with dissolution pores; (d) Well ST3, Devonian Guanwushan Formation, Central Sichuan Basin, bioclastic shoal facies dolomite with dissolution pores; (e) Well ST3, Devonian Guanwushan Formation, Central Sichuan Basin, bioclastic shoal facies dolomite with dissolution vugs.
Figure 7. Core Photographs of Ultra-Deep Reservoirs in Sichuan Basin. (a) Well PT101, Sinian Deng-2 Member, Central Sichuan Basin, thrombolite dolomite with well-developed dissolution vugs; (b) Well PS6, Sinian Deng-4 Member, Central Sichuan Basin, thrombolite dolomite with needle-like dissolution pores; (c) Well PS11, Cambrian Longwangmiao Formation, Central Sichuan Basin, grainstone dolomite with dissolution pores; (d) Well ST3, Devonian Guanwushan Formation, Central Sichuan Basin, bioclastic shoal facies dolomite with dissolution pores; (e) Well ST3, Devonian Guanwushan Formation, Central Sichuan Basin, bioclastic shoal facies dolomite with dissolution vugs.
Applsci 15 11380 g007
Applsci 15 11380 g010
Figure 10. Cross-Section of Sinian–Upper Paleozoic Gas Reservoirs in Northern Slope Zone of Sichuan Basin [1].
Figure 10. Cross-Section of Sinian–Upper Paleozoic Gas Reservoirs in Northern Slope Zone of Sichuan Basin [1].
Applsci 15 11380 g010
Applsci 15 11380 g011
Figure 11. Superimposed Map of Key Geological Units and Burial Depth in Sichuan Basin (a) Sinian Dengying Formation; (b) Cambrian Canglangpu and Longwangmiao Formation.
Figure 11. Superimposed Map of Key Geological Units and Burial Depth in Sichuan Basin (a) Sinian Dengying Formation; (b) Cambrian Canglangpu and Longwangmiao Formation.
Applsci 15 11380 g011
Applsci 15 11380 g012
Figure 12. Superimposed Map of Key Geological Units and Burial Depth in Sichuan Basin (a) Devonian–Carboniferous; (b) Permian-Triassic.
Figure 12. Superimposed Map of Key Geological Units and Burial Depth in Sichuan Basin (a) Devonian–Carboniferous; (b) Permian-Triassic.
Applsci 15 11380 g012
Table 1. Statistics of Plays in Key Deep and Ultra-Deep Formations of CNPC.
Table 1. Statistics of Plays in Key Deep and Ultra-Deep Formations of CNPC.
Serial NumberThe Field of
Oil and Gas
Exploration		BasinProspective BlockFavorable AreaRemaining Resources Estimation for the BlockBlock Ranking
Oil/108 tGas/1012 m3
1Marine Carbonate RocksSichuan BasinSlope belt of the paleo-uplift in the northwestern Sichuan Basin0.8 2.51
2Permian Platform Margin Belt in Sichuan Basin0.2 23
3Synclinal Area in the Eastern-Southern Sichuan Basin2.2 0.54
4Reef-Bank Complex in the Northern Rift Depression of the Sichuan Basin0.1 0.27
5Tarim BasinManxi Diliang Fault Zone in the Fuman Area0.75.2 5
6Fault-Controlled Cambrian Platform Margin Belt in the Lunnan Area0.3 0.68
7Fault-Controlled Ordovician Platform Margin Belt in the Gucheng Area 0.1 0.3 10
10Foreland Thrust BeltTarim BasinKuche Foreland Thrust Belt1.17.22.82
11 Junggar Basin Deep Structural Assemblage in the Southern Junggar Basin1.3 2.16
12Deep Shale GasSichuan BasinSilurian Strata in Southern Sichuan Basin0.7 8.79
Table 2. Detailed Parameters and Resource Potential of Ultra-Deep Reservoirs in Sichuan Basin.
Table 2. Detailed Parameters and Resource Potential of Ultra-Deep Reservoirs in Sichuan Basin.
RegionStrataBuried Depth Range (m)Reservoir
Thickness (m)		Type of TrapDistribution Area
(km2)		Favorable Area
(km2)		Resource
Potential (1012 m3)
Eastern SichuanDengying Formation6000–800010–100tectonic22,80040000.3
>800010–100tectonic21,80060000.9
Cambrian
Longwangmiao Formation		6000–800010–60/18,00045000.4
>800010–40/16,00020000.2
Cambrian
Canglangpu Formations		6000–80008–50Lithology19,00042000.5
>80008–40Lithology12,00012000.2
Carboniferous
Huanglong Formation		6000–800010–30Tectonic–stratigraphy15,00020000.5
>800010–30Tectonic–stratigraphy20005000.5
Western Sichuan–Northern SichuanSinian
Dengying Formation		6000–8000Deng-4: 50–170
Deng-2: 50–350		Lithology11,50049003.3
>8000Deng-4: 70–200
Deng-2: 50–400		Tectonic–lithology25,70077004.9
Cambrian
Longwangmiao Formation		6000–800010–60Lithology16,20025000.3
>800010–40Lithology10,00011000.1
Cambrian
Canglangpu Formations		6000–800010–60Lithology16,00043001.1
>800010–50Lithology400010000.4
Devonian–Carboniferous Guanwushan and Zongchanggou Formation6000–800010–20Tectonic–stratigraphy650025001
>800010–20Tectonic–stratigraphy550020001
Permian
Qixia Formations		6000–800018–45Tectonic–lithology/3500 (Enclosure area)0.4
Permian
Maokou Formation		6000–8000Maokou-2 period: 10–35Tectonic–lithology/5400 (Enclosure area)0.8
Permian
Changxing and Feixianguan Formations		>6000Changxing Formation: 10–100
Feixianguan Formation: 10–30		Tectonic–lithology/2700 (Enclosure area)0.7
Table 3. Thickness and Total Organic Carbon (TOC) Content of Ultra-Deep Source Rocks in Sichuan Basin.
Table 3. Thickness and Total Organic Carbon (TOC) Content of Ultra-Deep Source Rocks in Sichuan Basin.
RegionStrataAverage Total Organic Carbon ContentThickness (m)
Eastern SichuanLongmaxi>2%200–600
Qiongzhusi1.5%50–200
Doushantuo4.76%20–100
Western Sichuan–Northern SichuanLongmaxi>2%0–200
Qiongzhusi1.87%300–700
Maidiping1.8%30–130
Doushantuo3.9%10–300
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Zhou, G.; Zhang, Z.; Yan, Z.; Li, Q.; Chen, H.; Du, B. Ultra-Deep Oil and Gas Geological Characteristics and Exploration Potential in the Sichuan Basin. Appl. Sci. 2025, 15, 11380. https://doi.org/10.3390/app152111380

AMA Style

Zhou G, Zhang Z, Yan Z, Li Q, Chen H, Du B. Ultra-Deep Oil and Gas Geological Characteristics and Exploration Potential in the Sichuan Basin. Applied Sciences. 2025; 15(21):11380. https://doi.org/10.3390/app152111380

Chicago/Turabian Style

Zhou, Gang, Zili Zhang, Zehao Yan, Qi Li, Hehe Chen, and Bingjie Du. 2025. "Ultra-Deep Oil and Gas Geological Characteristics and Exploration Potential in the Sichuan Basin" Applied Sciences 15, no. 21: 11380. https://doi.org/10.3390/app152111380

APA Style

Zhou, G., Zhang, Z., Yan, Z., Li, Q., Chen, H., & Du, B. (2025). Ultra-Deep Oil and Gas Geological Characteristics and Exploration Potential in the Sichuan Basin. Applied Sciences, 15(21), 11380. https://doi.org/10.3390/app152111380

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop