Special Issue on “Recent Advances in Hydrocarbon Production Processes from Geoenergy”

1. Introduction

With the development of science and technology, the demand for oil and gas resources is increasing year by year. However, the recoverable reserves of conventional and readily accessible reservoirs are declining annually. It has become increasingly critical to enhance the development efficiency of unconventional oil and gas reservoirs in order to address growing energy demands and support sustainable development. Unconventional reservoirs typically refer to those with poor reservoir properties, such as low permeability and porosity, including shale oil and gas, tight oil and gas, coalbed methane, and deep reservoirs [1,2,3]. Commercial extraction from these reservoirs is generally attainable only through advanced technologies such as horizontal drilling, hydraulic fracturing, and acidization. Additionally, to maintain the productivity of unconventional wells during the mid-to-late development stages, timely water injection is necessary to replenish formation energy [4,5,6]. However, due to poor reservoir properties, the effect achieved by conventional water injection technology is often not satisfactory. This Special Issue of “Recent Advances in Hydrocarbon Production Processes from Geoenergy” in Processes has collected the latest research related to advanced stimulation and stabilization measures in the drilling and development of unconventional reservoirs, documenting data related to theoretical modeling, result analysis, and field applications of various technologies.

2. Advanced Analysis and Identification Technologies for “Sweet Spots” in Unconventional Hydrocarbon Reservoirs

The hydrocarbon characterization and monitoring analysis technology for unconventional reservoirs involves advancements in 3D seismic imaging, reservoir simulation, real-time monitoring systems, and artificial intelligence algorithms, etc., to enhance reservoir understanding and management, thereby achieving optimal production results [7,8]. Li et al. [9] studied the controlling factors of hydrocarbon enrichment in shale gas condensate reservoirs within rift lake basins. Through the application of geochemical pyrolysis logging, X-ray fluorescence (XRF) spectrum element logging, and SEM-based automated mineralogy, they found that thermal maturity thresholds, lithofacies assemblages, paleoenvironmental settings, and laminae and fracture systems are the main controlling factors for hydrocarbon enrichment in shale condensate gas reservoirs, and can be applied to the analysis and identification of “sweet spots” in unconventional reservoirs. Liu et al. [10] employed automatic mineral scanning equipment to obtain the microscopic physical property parameters of strata at continuous depths, and combined with the TOPSIS and AHP algorithms to optimize fracturing sweet spots in deep carbonate reservoirs. In addition, Li et al. [11] believe that the increase in oxygen content contributed to the biodiversity of the Fortunian stage in the Tarim Basin through the analysis of reservoir minerals and hydrocarbon compositions.

3. Advanced Hydraulic Fracturing Technologies for Unconventional Hydrocarbon Reservoirs

Hydraulic fracturing is one of the primary measures for production enhancement in unconventional reservoirs. With continuous research and development, current studies have gradually shifted from process optimization to mechanism research, focusing on related studies such as the optimization of hydraulic fracturing fracture parameters and the migration and placement laws of proppants in fractures, so as to improve the long-term conductivity of artificial fractures [12,13].

(1). Regarding the influencing factors of fracture propagation and hydraulic fracturing parameter optimization, Ma et al. [14] conducted simulation studies on the key factors affecting fracture propagation during hydraulic fracturing based on the displacement discontinuity method and a geological engineering integration method. The targeting reservoir types include shale, carbonate rock, volcanic rock, and deep coal seams.

(2). Regarding the influencing factors of fracture conductivity and optimization, Ci et al. [15] experimentally studied the impact of fracture angle, fracture number, proppant concentration, and closure pressure on fracture conductivity, providing theoretical support for constructing high-conductivity fracture networks in complex unconventional reservoirs.

(3). Regarding the research on proppant migration and placement behavior within fractures, Liang et al. [16] studied the migration and settlement laws of proppants in the sand-carrying fluid based on the power-law non-Newtonian fluid model, and the average relative error between the calculated settlement velocity and the actual settlement velocity was only 8.2%. Additionally, Zheng et al. [17] explored the application of CO₂ dry fracturing technology in shale reservoirs, contributing to the advancement of carbon neutrality and carbon storage initiatives within the petrochemical industry.

4. Stabilization Supporting Technologies for Unconventional Reservoir

To maintain the productivity of unconventional reservoirs during mid-to-late stages, emphasis has been placed on the flow laws of oil–water and gas–liquid two-phase flow, as well as the technology of large-volume water injection in low-permeability reservoirs to replenish formation energy [18,19]. Cheng et al. [20] employed both experimental and numerical simulation methods, integrated with a convolutional neural networks, to conduct comprehensive simulations on the flow behaviors of oil–water and gas–liquid two-phase flows in pipelines and annular geometries, thereby enhancing the efficiency of oil–water transportation and improving the accuracy of flow pattern recognition. To rapidly and efficiently inject fluids into the formation, replenish reservoir energy, and sustain oil and gas well production, Li et al. [21] investigated high-pressure water injection technology under near-fracturing pressure conditions in low-permeability reservoirs. This technology utilizes high pressure to alter reservoir physical properties and enhance the formation’s water absorption capacity at the injection end, thereby significantly improving the waterflooding recovery factor in low-permeability reservoirs.

5. Conclusions

The papers in this Special Issue present the latest theoretical advancements on the stimulation and production stabilization technologies for unconventional reservoirs. Due to the complex geological structures and poor reservoir properties of unconventional reservoirs, a series of technological innovations in drilling and development are required to achieve commercial exploitation and long-term stable production, providing a sustained energy supply for high-quality development of humanity. We hope that this Special Issue can clarify current and emerging research activities related to several key technologies in unconventional reservoir development, promoting the efficient exploitation of such reservoirs.