Search Results (8)

Intrabasinal low uplifts in lacustrine rift basins are key targets for sedimentological and petroleum geological research, as they can act as local source areas and exert critical controls on intrabasinal “source-to-sink” systems. Due to the discontinuous sediment supply, these systems often demonstrate the subtle and intermittent nature, and their roles in the development of depositional systems are usually overlooked. To clarify the controlling effect of intrabasinal local provenances on sedimentary system evolution, this study reconstructed the dynamic tectonic evolution of the Weixinan Low Uplift in the Beibuwan Basin, and systematically analyzed its control on “source-to-sink” systems and sedimentary filling using integrated high-resolution 3D seismic, core, well logging and geochemical data. Our results demonstrate that the activity of Fault 3 dominated the paleogeomorphic evolution of the Weixinan Low Uplift and its surrounding areas, which further governed the spatiotemporal development of the “source-to-sink” system and the distribution of sedimentary systems, with distinct evolutionary stages as follows: During the Ls2 Member stage (48.6–40.4 Ma), Fault 3 was inactive, the Weixinan Low Uplift was manifested as a gently dipping subaqueous slope under the influence of regional lacustrine transgression, and only small-scale braided river deltas were developed on the slope belt with weak sediment supply from the Qixi Uplift. During the Ls1 Member stage (40.4–33.9 Ma), the Ls13 Sub-member stage (lower Ls1 Member stage) was characterized by initiation of Fault 3 with segmented activity, triggering the formation of the Eastern Sub-sag of the Haizhong Sag and subaqueous uplift of the Weixinan Low Uplift; clastic sediments from the central Qixi Uplift were transported northeastward, developed braided river deltas and large-scale basin-floor lacustrine fans. In the Ls12 Sub-member stage (middle Ls1 Member stage), Fault 3 continued to propagate and was gradually linked, leading to further uplift of the Weixinan Low Uplift and expansion of the Haizhong Sag; Clastic materials from the central Qixi Uplift were almost entirely trapped in the Eastern Sub-sag of the Haizhong Sag. During the Ls11 Sub-member stage (upper Ls1 Member stage), further intensification of Fault 3 activity caused the Weixinan Low Uplift to be subaerially exposed and evolve into an intrabasinal local provenance, which supplied clastic sediments to surrounding sags and developed braided river deltas on the gentle slope belts and small-scale lacustrine fans on the lower slope. This study demonstrates that the tectonic evolution of the Weixinan Low Uplift has induced prominent changes in the basin paleogeomorphology, which in turn triggered dynamic shifts in the provenance and sediment transport pathways, and thus gave rise to complex local “source-to-sink” systems and depositional styles. Full article

The Sinian (Ediacaran) Dengying Formation in the northeastern Sichuan Basin exhibits a significant exploration potential. Nevertheless, the great burial depth of carbonates in the Dengying Formation and the scarcity of drilling data have imposed constraints on in-depth investigations into the evolution of lithofacies paleogeography as well as the primary controlling mechanisms. Through integrated analysis of field outcrops, core and well logging data, the evolution of the lithofacies and paleogeography of the Dengying Formation in the northeastern Sichuan Basin was reconstructed by using 3D stratigraphic forward modeling. The study area is predominantly characterized by platform margin facies and restricted platform facies, comprising four subfacies including microbial (algal) mound, grain shoal, intershoal sea, and intraplatform depression. The microbial (algal) mound and grain shoal subfacies are primarily developed along the western and eastern platform margins, exhibiting a near north–south trend. Scattered mound–shoal complexes and intershoal sea occur within the platform, with localized intraplatform depression zone. During the depositional stage of the Dengying Formation, three primary paleogeomorphic units were developed including the platform margin topographic high zone, intraplatform gentle slope zone, and intraplatform depression zone. During the Deng-1 and Deng-3 periods, sea level rise increased accommodation space, leading to a gradual decline in carbonate productivity and limited development of the mound–shoal complexes. In contrast, during the Deng-2 and Deng-4 periods, sea level decreased, water depth decreased, and carbonate productivity was enhanced, resulting in extensive development of the mound–shoal complexes. The simulation results indicate that carbonate-producing ecosystems thrive when wind blows from 270° W (80% frequency) or 15° N (60% frequency); with an effective water depth of 10–20 m, the elevated carbonate productivity is conducive to the growth of biogenic calcification. Comprehensive analysis suggests that paleogeomorphology, eustatic fluctuations, and paleowind fields collectively control the distribution and evolution of the lithofacies in the Dengying Formation in the northeastern Sichuan Basin. Paleogeomorphology governs the types and distribution of sedimentary facies belts as well as the spatial arrangement of lithofacies. Eustasy determines the magnitude of mound–shoals and their lateral migration. Three-dimensional stratigraphic forward modeling offers a novel approach for reconstructing paleogeographic evolution of carbonate platforms and analyzing key controlling factors, while also enhancing our ability to predict the distribution patterns of mound–shoal complexes. Full article

As a significant hydrocarbon-bearing sag in the Zhu I Depression of the Pearl River Mouth Basin, the Lufeng sag has long encountered exploration challenges owing to the dearth of comprehensive investigations on the source-to-sink system of the steep slope zone. To tackle this issue, this research utilizes paleogeomorphic reconstruction techniques to conduct a quantitative source-to-sink analysis and establish a hydrocarbon accumulation pattern in the steep slope zone of ductile deformation zones. The findings indicate that the longitudinal drainage systems developed during the intense rifting stage determine the proximal sedimentation. During the minor rifting stage, the area of the lacustrine basin contracted, and the pre-existing drainage systems converged into axial drainage systems. By the late rifting stage, the extent of the drainage system expands significantly, displaying distal sediment source characteristics. The tectono-geothermal regime governs the spatial scale of the source-to-sink system. Quantitative analysis reveals that the denudation and depositional areas in the ductile deformation zones notably exceed those in the brittle deformation zones, thereby creating favorable conditions for the large-scale development of sand bodies and hydrocarbon accumulation in the steep slope zone. These insights offer crucial guidance for future exploration in the steep slope zones of the fault basin. Full article

The Changling Depression, located in the southern part of the central depression zone of the Songliao Basin, is characterized by complex structures and has been shaped by multiple phases of tectonic activity. The strata in this region have undergone significant uplift and denudation, resulting in an incomplete understanding of the prototype basin and hindering progress in oil and gas exploration. To better understand the geological characteristics and exploration potential of the Changling Depression, this study begins with the reconstruction of denudation amounts. Using the stratigraphic trend extrapolation method, the denudation of strata during the faulting period of the Changling Depression is quantified. By combining the denudation thickness with the remaining strata thickness, the original strata thickness is restored. Employing MOVE 2018version and Petrel 2021version software, the paleogeomorphology of different geological periods is reconstructed. Through an analysis of the prototype basin’s structure, its evolution history, sedimentary filling patterns, and paleogeomorphological features, it is determined that the maximum depositional thickness and rate during the Huoshiling period occurred in the Shenzijing, Heidimiao, and Fulongquan areas, with strong central deposition that weakened toward the north and south. During the Shahezi period, depositional thickness and rates exhibited a pattern of weaker deposition in the south and stronger in the north. In the Yingcheng Formation–Denglouku Formation period, the basin entered a subsidence phase, with an expanded range of strata subsidence. During the Denglouku period, the Qianbei area experienced strong deposition, while the Heidimiao area saw even more pronounced deposition; in contrast, the Shenzijing area displayed very weak depositional activity. The study reveals a south-to-north migration of lateral subsidence centers over time, influenced by left-lateral tectonic forces, reflecting a shift in the dominant influence pattern. These findings clarify the morphology of the prototype basin and the distribution and migration of subsidence centers across different periods, providing valuable insights that will facilitate deeper oil and gas exploration efforts in the Changling Depression. Full article

Thin layers and high-yield dolomite reservoirs were recently discovered in the Permian Guadeloupian Maokou Formation. The genetic mechanism of this reservoir is controversial because of its complex sedimentation and diagenesis in the Maokou Formation. Traditionally, the genesis has focused on sedimentation, karst, and fracture, whereas the influence of the Emeishan mantle plume activity (EMP) has been ignored. In this study, we enumerated petrographic (grouped into micritic bioclastic limestone, limy dolomite, grain dolomite, dolomite cement, calcite cement, and saddle dolomite) and geochemical data (δ¹³C, δ¹⁸O, REE, and ⁸⁷Sr/⁸⁶Sr) from a microscopic perspective to support the impact of EMP on reservoirs. We conclude that EMP activity altered the sedimentary environment and induced a complex diagenesis. The paleogeomorphic reconstruction data indicate that the EMP caused an uplift zone in the NE–SW direction, depositing advantageous high-energy beach facies. In terms of diagenesis, the abnormally high ⁸⁷Sr/⁸⁶Sr ratios and REE with positive Eu anomalies suggest that dolomitization was influenced by both seawater and hydrothermal fluids. Based on the above evidence, we established a reservoir genetic model for the Maokou Formation related to the intensity of the EMP. This study provides a new perspective on the mantle plume activity for the study of carbonate reservoir genesis. Full article

The Benxi Formation is one of the most important gas-producing layers in the Ganquan–Fuxian area, but the complex gas–water distribution and lack of sandstone have severely constrained natural gas exploration and development in this area. This study analyzed the structure, paleogeomorphology, sedimentary facies, reservoir closures, and gas–water distribution of the Benxi Formation in the study area through drilling, coring, logging, seismic surveying, and experimental testing. The results show that the gas reservoirs in the Benxi Formation are mainly lithologic traps distributed along NW-trending barrier sandstones, with a small portion of updip pinchout closures. The water layers are mainly composed of thin sandstones with a single-layer thickness of less than 2 m, which are tidal-channel or barrier-margin microfacies sandstones. The water saturation in some thick sandstones is related to the activity and destruction of large individual faults. The dry layers are tight sandstones with porosity of less than 3.2%, mainly associated with high amounts of volcaniclastic matrix and lithic fragments, as well as compaction. The charging of the underlying high-quality Ordovician limestone reservoirs by carboniferous source rocks in the Benxi Formation reduces the probability of gas accumulation in Benxi sandstone. Based on the control of sedimentary facies and physical properties on gas accumulation, favorable reservoir distributions were predicted using seismic attributes and gas detection methods, providing the basis for the next phase of natural gas exploration and development in this area. Full article

Large fault belts often influence the paleo-geomorphic changes in basins and control hydrocarbon accumulation and distribution in basins. Based on the gravity field model European Improved Gravity model of the Earth via New techniques (EIGEN)-6C4, this study calculated the residual Bouguer gravity disturbance of the Tarim Basin by using the minimum curvature method and analyzed gravitational characteristics of major fault belts of the Tarim Basin. The residual Bouguer disturbance exhibits linear residual Bouguer disturbance zones in the Tianshan Mountains, West Kunlun, and the Altyn region, which is consistent with the spatial distribution of their related fault belts. The regional Bouguer disturbance is related to crust–mantle boundary depth, which can be used to roughly estimate crust thickness. Thus, we suggest that the crust–mantle boundary depth order of major faults from deep to shallow is the Altyn region, West Kunlun, and Tianshan Mountains. There is a discontinuity in the residual Bouguer disturbance of West Kunlun, which compares well with the fault belt of West Kunlun. Furthermore, the residual Bouguer disturbance of the Tarim Basin has a series of elliptical areas with a central positive disturbance located within the Bachu uplift and other uplift structures. The residual Bouguer disturbance also reflects the position and distribution of the major fault belts and the boundary of the Tarim Basin, which can provide guidance for dynamic evolution analysis of large basins. Full article

The sedimentary characteristics of the Neogene in the eastern Liaodong area are poorly studied, which restricts the oil and gas exploration in this area. Based on the current seismic, logging, drilling, and core data, we have studied the sequence stratigraphy and sedimentary characteristics of the Neogene in the eastern Liaodong area. Ultimately, we identified the controlling factors of sedimentation and established the depositional model. In this study, six sequence boundaries of the Neogene were identified and can be divided into five third-order sequences. The sedimentary evolution can be divided into four stages: braided river delta, meandering river delta with a low sand-stratum ratio, meandering river delta with a high sand-stratum ratio, and meandering river delta. Both the palaeotectonic movements and paleoclimate changes of the Neogene influence the periodical fluctuation of the lake level and then control the vertical evolution of the sedimentary types. The paleogeomorphology controls the macroscopic distribution of the sedimentary facies zone, the paleo-valleys that are associated with the strike-slip faults control the channel strike, and the fault slopes at the edge of the lacustrine basins control the sand redistribution of the delta front. Full article