Based on the molecular structure transitions, hydrocarbon composition, and reservoir characteristics changes during coal evolution, combined with the production characteristics of coal-rock gas, the generation stages and genetic types of coal-rock gas in China are investigated. The generation of coal-rock gas can be divided into five stages: low-coal-rank biogenic gas generation stage (Ro < 0.5%), mid-coal-rank transitional gas generation stage (0.5% ≤ Ro < 0.8%), mid-coal-rank mature gas generation stage (0.8% ≤ Ro < 1.3%), mid-coal-rank high-maturity gas generation stage (1.3% ≤ Ro < 2.0%), and high-coal-rank overmature gas generation stage (Ro ≤ 2.0%). Based on the burial depth and gas origin, the gas reservoirs are divided into three types: shallow coalbed methane, deep coal-rock gas and exogenous coal-rock gas. According to the hydrocarbon generation stage of coal, deep coal-rock gas is further classified into: mid-coal-rank transitional coal-rock gas, mid-coal-rank mature coal-rock gas, mid-coal-rank high-maturity coal-rock gas, and high-coal-rank overmature coal-rock gas. During the dynamic evolution of coal from shallow to deep depths, the coal has experienced a hydrocarbon generation evolution sequence of “biogenic gas→transitional gas→wet gas→dry gas”, and a process of “primary pores→cleat development→peak organic matter pores→densification and fracturing + fracture opening” of reservoirs formation . The occurrence state gradually shifts from “dominance of adsorbed gas” to “continuous increase in free gas proportion”, and the development modes also transform from “long-term drainage and depressurization for desorption” to “high gas production upon well opening”. In addition, there is another type of coal-rock gas which is externally sourced, with the natural gas originating from underlying strata. This type of coal-rock gas corresponds to low-rank coals with reservoir development, where gas was accumulated under the control of tectonics, with high-proportion free gas and high initial production.

To accurately evaluate the storage capacity of shale oil reservoirs under in-situ temperature and pressure conditions, we constructed a new model for determining the porosity under formation conditions, developed a HTHP shale porosity measurement system capable of operating at an overburden pressure of 70 MPa, a pore-fluid pressure of 40 MPa, and a temperature of 120 °C, and established an integrated workflow for restoring in-situ porosity in clay-rich lacustrine shale oil reservoirs. This technology system was applied to the Upper Cretaceous Gulong shale oil reservoirs in the Songliao Basin, China. The in-situ porosity in shale oil reservoirs is generally higher than that measured at normal pressure on surface. The restored porosity increases by 3.17–4.00 percentage points for ordinary shale, 1.58–1.60 percentage points for silty shale, and 1.12–1.58 percentage points for carbonates. The restored porosity increase grows regularly with burial depth, temperature, pore pressure, and pressure coefficient, reflecting the elastic dilation of clay- and organic-associated nanopores and the widening of overpressure-supported microfractures in the Gulong shales. Core depressurization was found to close these pressure-supported pores, causing conventional helium and surface nuclear magnetic resonance (NMR) measurements to systematically underestimate storage capacity, particularly in deep, clay-rich, overpressured intervals. For reserve estimation, use of ambient-condition porosity may introduce significant underestimation of original oil in place (OOIP). For the clay-rich Gulong shales, it is recommended to apply a correction factor of 3–4 percentage points to the surface-measured porosity (or surface porosity) for ordinary shale, and about 1.6 percentage points for silty shale, while only a minor correction is needed for carbonates. In-situ porosity should thus be incorporated into OOIP calculations and parameterized using clay content, total organic carbon content, pressure coefficient and burial depth. Operationally, production from clay-rich, overpressured intervals should be implemented under controlled pressure, in order to avoid elastic closure of native microfractures and preserve reservoir deliverability.

Through tracing the background and customary usage of classification of fine-grained sedimentary rocks and terminology, and comparing current “sedimentary petrology” textbooks and monographs, this paper proposes a classification scheme for fine-grained sedimentary rocks and clarifies related terminology. The comprehensive analysis indicates that the classification of clastic rocks, volcanic clastic rocks, chemical rocks, and biogenic (carbonate) rocks is unified, and the definitions of terms such as lamination, bedding and beds are consistent. However, there is a disagreement on the definition of “mud”. European and American scholars commonly use the term “mud” to include silt and clay (particle size less than 0.062 5 mm). Chinese scholars equate the term “mud” to “clay” (particle size less than 0.003 9 mm or less than 0.01 mm). Combined with the discussion on terms such as sedimentary structures (bedding, lamination and lamellation), shale, mudstone, mudrocks/argillaceous rocks and mud shale, it is recommended to use “fine-grained sedimentary rocks” as the general term for all sedimentary rocks composed of fine-grained materials with particle size less than 0.062 5 mm, including claystone/mudrocks and siltstone. Claystone/mudrocks are further classified into argillaceous (or clayey) mudstone/shale, calcareous mudstone/shale, siliceous mudstone/shale, silty mudstone/shale and silt-containing mudstone/shale. Argillaceous (or clayey) mudstone/shale emphasizes a content of clay minerals or clay-sized particles exceeding 50%. Other mudstones/shales emphasize a content of particles (particle size less than 0.062 5 mm) exceeding 50%. The commonly referred term “shale” should not include siltstone. It is necessary to establish a reasonable, standardized, and applicable classification scheme for fine-grained sedimentary rocks in the future. An integrated shale microfacies research at the thin-section scale should be carried out, and combined with well logging data interpretation and seismic attribute analysis, a geological model of lithology/lithofacies will be iteratively upgraded to accurately determine sweet layer, locate target layer, and evaluate favorable area.

The shale oil phase state is essential for assessing shale oil production, establishing development plans, and enhancing oil recovery. Previous studies on shale oil phase state mainly focused on bulk fluid phase based on fluid composition retrieved from drill holes, while nano-confined shale oil phase state based on subsurface in-situ fluid compositions is rarely discussed. In this work, we established a new workflow that used pressure-preserved shale cores and pyrolysis gas chromatogram (Py-GC) to retrieve in-situ shale oil compositions from various shales with different thermal maturities. The workflow includes retrieving pressure-preserved shale cores, cutting, transporting, and then preparing samples under the protection of liquid nitrogen; the new process makes the evaporation loss of lightweight hydrocarbons the least. By comparison, fluid samples from wellheads and wellbores were also retrieved from Gulong shale oil reservoirs in the Songliao Basin. Both bulk and nano-confined shale oil phases were then analyzed, and the results showed that methane content in the Gulong shale oil increased from 10.11 to 23.39% with increasing thermal maturity; by contrast, C7+ hydrocarbons decreased from 64.73 to 41.13%. As for bulk fluid phases, Gulong shale oils are black oil phases, while in terms of nano-confined fluid phases, their phases are controlled by thermal maturity. They are black oil phases at lower thermal maturity with vitrinite reflectance (Ro) less than 1.4% and are condensate phases at higher thermal maturity with Ro greater than 1.4%. Shale oil production data showed that nano-confined phase analysis using in-situ shale oil compositions from pressure-preserved cores can best predict shale oil production in this study.

A new pore type, nano-scale organo-clay complex pore-fracture was first discovered based on argon ion polishing-field emission scanning electron microscopy, energy dispersive spectroscopy and three-dimensional reconstruction by focused ion-scanning electron in combination with analysis of TOC, Ro values, X-ray diffraction etc. in the Cretaceous Qingshankou Formation shale in the Songliao Basin, NE China. Such pore characteristics and evolution study show that: (1) Organo-clay complex pore-fractures are developed in the shale matrix and in the form of spongy and reticular aggregates. Different from circular or oval organic pores discovered in other shales, a single organo-clay complex pore is square, rectangular, rhombic or slaty, with the pore diameter generally less than 200 nm. (2) With thermal maturity increasing, the elements (C, Si, Al, O, Mg, Fe, etc.) in organo-clay complex change accordingly, showing that organic matter shrinkage due to hydrocarbon generation and clay mineral transformation both affect organo-clay complex pore-fracture formation. (3) At high thermal maturity, the Qingshankou Formation shale is dominated by nano-scale organo-clay complex pore-fractures with the percentage reaching more than 70% of total pore space. The spatial connectivity of organo-clay complex pore-fractures is significantly better than that of organic pores. It is suggested that organo-complex pore-fractures are the main pore space of laminar shale at high thermal maturity and are the main oil and gas accumulation space in the core area of continental shale oil. The discovery of nano-scale organo-clay complex pore-fractures changes the conventional view that inorganic pores are the main reservoir space and has scientific significance for the study of shale oil formation and accumulation laws.

This study took the Gulong Shale in the Upper Cretaceous Qingshankou Formation of the Songliao Basin, NE China, as an example. Through paleolake-level reconstruction and comprehensive analyses on types of lamina, vertical associations of lithofacies, as well as stages and controlling factors of sedimentary evolution, the cyclic changes of waters, paleoclimate, and continental clastic supply intensity in the lake basin during the deposition of the Qingshankou Formation were discussed. The impacts of lithofacies compositions/structures on oil-bearing property, the relation between reservoir performance and lithofacies compositions/structures, the differences of lithofacies in mechanical properties, and the shale oil occurrence and movability in different lithofacies were investigated. The insights of this study provide a significant guideline for evaluation of shale oil enrichment layers/zones. The non-marine shale sedimentology is expected to evolve into an interdisciplinary science on the basis of sedimentary petrology and petroleum geology, which reveals the physical, chemical and biological actions, and the distribution characteristics and evolution patterns of minerals, organic matter, pores, fluid, and phases, in the transportation, sedimentation, water-rock interaction, diagenesis and evolution processes. Such research will focus on eight aspects: lithofacies and organic matter distribution prediction under a sequence stratigraphic framework for non-marine shale strata; lithofacies paleogeography of shale strata based on the forward modeling of sedimentation; origins of non-marine shale lamina and log-based identification of lamina combinations; source of organic matter in shale and its enrichment process; non-marine shale lithofacies classification by rigid particles + plastic components + pore-fracture system; multi-field coupling organic-inorganic interaction mechanism in shale diagenesis; new methods and intelligent core technology for shale reservoir multi-scale characterization; and quantitative evaluation and intelligent analysis system of shale reservoir heterogeneity.

Lacustrine systems since the Mesozoic have sequestered large quantities of organic carbon, which may have important value for global climate cooling, but there is still a lack of geological evidence of this sequestration. Taking the Songliao Basin in China as a case study, we elucidate the important function of lacustrine basins as sinks of a large amount of organic carbon, particularly when the contemporaneous marine sediments were poor sinks of organic carbon. Volcanic activities and orbital forcing were likely key factors influencing the water transportation between the land and oceans, as well as the alternating burial of organic carbon in the oceans and land. Microorganisms related to methane metabolism may have been highly involved in the mineralization and sequestration of lacustrine organic carbon. This study provides new insights into the coupled carbon-water cycle between the land and oceans and the influence of this process on global climate evolution.

Based on the results of drilling, tests and simulation experiments, the shales of the Cretaceous Qingshankou Formation in the Gulong Sag of the Songliao Basin are discussed with respect to hydrocarbon generation evolution, shale oil occurrence, and pore/fracture evolution mechanism. In conjunction with a substantial amount of oil testing and production data, the Gulong shale oil enrichment layers are evaluated and the production behaviors and decline law are analyzed. The results are drawn in four aspects. First, the Gulong shales are in the stage of extensive hydrocarbon expulsion when Ro is 1.0%–1.2%, with the peak hydrocarbon expulsion efficiency of 49.5% approximately. In the low–medium maturity stage, shale oil migrates from kerogen to rocks and organic pores/fractures. In the medium–high maturity stage, shale oil transforms from adsorbed state to free state. Second, the clay mineral intergranular pores/fractures, dissolution pores, and organic pores make up the majority of the pore structure. During the transformation, clay minerals undergo significant intergranular pore/fracture development between the minerals such as illite and illite/smectite mixed layer. A network of pores/fractures is formed by organic matter cracking. Third, free hydrocarbon content, effective porosity, total porosity, and brittle mineral content are the core indicators for the evaluation of shale oil enrichment layers. Class-I layers are defined as free hydrocarbon content equal or greater than 6.0 mg/g, effective porosity equal or greater than 3.5%, total porosity equal or greater than 8.0%, and brittle mineral content equal or greater than 50%. It is believed that the favourable oil layers are Q2–Q3 and Q8–Q9. Fourth, the horizontal wells in the core area of the light oil zone exhibit a high cumulative production in the first year, and present a hyperbolic production decline pattern, with the decline index of 0.85–0.95, the first-year decline rate of 14.5%–26.5%, and the single-well estimated ultimate recovery (EUR) greater than 2.0×104 t. In practical exploration and production, more efforts will be devoted to the clarification of hydrocarbon generation and expulsion mechanisms, accurate testing of porosity and hydrocarbon content/phase of shale under formation conditions, precise delineation of the boundary of enrichment area, relationship between mechanical properties and stimulated reservoir volume, and enhanced oil recovery, in order to improve the EUR and achieve a large-scale, efficient development of shale oil.

This paper systematically reviews the trend of carbon dioxide capture, utilization and storage (CCUS) industry in the world and China, presents the CCUS projects, clusters, technologies and strategies/policies, and analyzes the CCUS challenges and countermeasures in China based on the comparison of CCUS industrial development at home and abroad. The global CCUS development has experienced three stages: exploration stage, policy driven stage, and dual-drive stage. Currently, the active large-scale CCUS projects around the world focus on enhanced oil recovery (EOR) and are expanding into storage in saline aquifers. The CCUS industry of China has evolved in three stages: exploration, pilot test, and industrialization. In the current critical period of transition from field test to industrialization, China's CCUS projects are EOR-dominated. By comparing the industrial development of CCUS in China and abroad, it is found that the scale-up and industrialization of CCUS in China face challenges in technology, facilities and policies. Finally, future solutions to CCUS development in China are proposed as follows: strengthening the top-level design and planning of CCUS; developing high-efficiency and low-cost CCUS technologies throughout the whole industrial chain; deploying CCUS oil and gas + new energy clusters; improving the policy support system of CCUS; and strengthening discipline construction and personnel training, etc.

The Cretaceous Gulong shale oil reservoirs in the Songliao Basin are composed of organic-rich continental shales with high clay content,interbedded with minor amounts of thinly laminated calcareous sandstones and dolomites.Currently,there is a lack of studies on the pore-fissure system and shale oil enrichment pattern of these reservoirs.Based on the data from experiments and analyses including argon ion milling-field emission scanning electron microscopy(FE-SEM),energy-dispersive X-ray spectroscopy(EDS),high-pressure mercury injection analysis,low-temperature nitrogen adsorption experiment,fluorescence thin section observation,X-ray diffraction(XRD)mineralogy of whole rock,and geochemical analysis,we investigate the organic-inorganic pore-fissure system in the Gulong shale and its relationship with shale oil enrichment.The results are as follows:(1)The Gulong shale hosts a dual-porosity reservoir system consisting of matrix pores and microfissures.Matrix pores serve as shale oil enrichment spaces,while microfissures provide both storage spaces and seepage pathways for shale oil;(2)Influenced by multiple factors such as mineral evolution,hydrocarbon generation,and cracking and conversion of crude oil,the Gulong shale exhibits varying pore-fissure combinations at different evolutionary stages.At the mature stage,the shale predominantly contains micron-scale dissolved pores and organo-clay complex pores/fissures(i.e.,pores/fissures with clay minerals as framework and formed as a result of hydrocarbon generation).In contrast,the highly mature stage is characterized by nano-scale organo-clay-complex pores/fissures and bedding fissures;(3)There exists a coupling relationship between the shale oil enrichment and the evolution of pore-fissure combinations for the Gulong shale.The shale oil primarily accumulates within inorganic intergranular and intercrystalline pores at the low mature stage,while it is relatively heavy and predominantly concentrates in dissolved pores and organo-clay complex pores/fissures at the mature stage.At the highly mature stage,the shale oil becomes lighter and largely gets enriched in organo-clay complex pores/fissures and bedding fissures.

The clay mineral content of Daqing Gulong shale is in the range of about 35%–45%, with particle sizes less than 0.0039 mm. The horizontal fluidity of oil in Gulong shale is poor, with near-zero vertical flowability. As a result, Gulong shale has been considered to lack commercial value. In recent years, however, interdisciplinary research in geoscience, percolation mechanics, thermodynamics, and surface mechanics has demonstrated that Gulong shale oil has a high degree of maturity and a high residual hydrocarbon content. The expulsion efficiency of Gulong shale in the high mature stage is 32%–48%. Favorable storage spaces in Gulong shale include connecting pores and lamellar fractures developed between and within organic matter and clay mineral complexes. The shale oil mainly occurs in micro- and nano-pores, bedding fractures, and lamellar fractures, with a high gas–oil ratio and medium–high movable oil saturation. Gulong shale has the characteristics of high hardness, a high elastic modulus, and high fracture toughness. This study achieves breakthroughs in the exploration and development of Gulong shale, including the theories of hydrocarbon generation and accumulation, the technologies of mobility and fracturing, and recoverability. It confirms the major transition of Gulong shale from oil generation to oil production, which has extremely significant scientific value and application potential for China's petroleum industry.

The deeply buried Ordovician Lianglitage Formation (>6500 m) in the Halahatang area, Tarim Basin, is characterized by a paleokarst topography and subsurface, collapsed paleokarstsystems. Based on core and thin-section observation and wireline-log interpretation, this study analyzed basic features of collapsed karst systems and mapped the pattern of collapsed and original karst systems through root mean square (RMS) amplitude and variance attribute fusion. Employment of production data revealed the general rule of these ultra-deep, buried, collapsed systems as reservoirs for oil and gas. This study showed that epigenic subsurface karst systems in the Lianglitage Formation experienced full collapse, filling, and subsequent strong compaction. Passages of subsurface karst systems have a dendritic pattern These ultra-deep and strongly compacted collapsed systems are not favorable for oil and gas production owing to poor reservoir qualities. Factors controlling original subsurface karst development in this area are extensive subaerial exposure during the Falling-Stage Systems Tract (FSST) and Lowstand Systems Tract (LST) periods following deposition of the Lianglitage Formation, faults and fractures formed before or during karstification, and surface drainage systems on top of the Lianglitage unconformity. This study provides a method to comprehensively characterize the features, distribution and mechanism of the ultra-deep buried epigenic karst reservoirs and clarified their low potential as reservoirs for oil/gas exploration and development. It also helps clarify that the true oil pay reservoirs in this reservoir resulted from hypogene dissolution rather than epigenic karst.

预计未来数十年油气仍将保持全球主体能源地位.全球气候治理将大幅提高油气综合成本,这对油气行业未来发展构成了巨大挑战.勘探开发投资增长前景并不乐观,未来全球油气稳定供应的风险将大大增加.社会发展对油气资源的需求仍是中国油气行业需要解决的关键问题.在碳中和目标下,中国油气行业面临发展和转型的双重压力,近中期需同时关注能源安全和低碳转型.一方面,通过技术创新攻克难题,在陆上深层、超深层石油天然气资源勘探与开发,老油田大幅度提高采收率,海洋油气勘探与开发以及非常规油气勘探与开发等领域形成突破,实现"稳油增气",保障国家能源安全;另一方面,智慧油田、超级盆地多资源协同发展、新一代工程技术和CCUS技术等是石油天然气行业降低碳排放的重要领域.

Continental shale oil is a new source of oil, and its formation and evolution mechanism is one of the most important scientific problems in its effective exploration and development. In this work, the hydrocarbon generation mechanism, occurrence of oil and gas, and pore structure characteristics were studied through a series of pyrolysis experiments using an improved closed experimental system, combined with chloroform extraction, two-dimensional nuclear magnetic resonance, and computed tomography, for the continental Gulong Shales, Songliao Basin. The results show that hydrocarbon generation from organic matter of continental Gulong shale follows a sequential reaction model, with adsorbed oil as an "intermediate " at Ro of 0.9-1.1%. The free oil reaches the generation peak and begins to convert to natural gas, and the gas/oil ratio increases rapidly when Ro > 1.3%. These suggest that the favorable oil generation window for Gulong shale is that Ro is between 0.9 and 1.6%. With oil generation, the shale pore structure and permeability change with maturity accordingly. The corresponding Ro for rapid porosity and pore volume increase is 0.9-1.2%, while Ro is greater than 1.2% for rapid permeability change as a result of the large amount of adsorbed oil converting into free oil. It is found that hydrocarbon generation and pore-forming materials are mostly lamalginite and the organic-clay complex, and their volumes shrank while generating hydrocarbon, forming pores and fractures along the layers and "sponge-like " pores, respectively. When Ro > 1.2%, the shale oil generation peak, pore development peak, and overpressure evolution peak are coupled, providing favorable conditions for shale oil and gas enrichment in continental Gulong shale. These experimental findings mutually prove and confirm the practice of Gulong shale oil exploration, and it may have important theoretical and practical significance for continental shale oil exploration and discovery in other basins.

一个油气藏从油气生成到消亡的进程,与其所经历的地质历史、地质作用和人工开采因素有关.人工开采加快油气藏消亡的进程,开发方式和技术手段不同会影响油田的开发生命周期.通过不断创新应用方法和技术,增加地质储量和可采储量,可有效延长油田的开发生命周期.根据大庆油田萨北开发区不同开发阶段的特点和矛盾,以提高油田采出程度为主线,论述了以早期注水、分层开采、加密调整为主的二次采油技术和以聚合物驱、三元复合驱为主的三次采油技术以及以自适应驱油体系为主的化学驱后四次采油技术对延长萨北开发区开发生命周期的开发实践.未来勘探开发技术水平的不断提高,将增加油田地质储量和可采储量,基于翁氏预测模型和偏正态分布数学模型,预计萨北开发区可以开采至2110年以后.

Some unusual events happened in petroleum industry in 2020, such as the negative WTI oil price, price soaring of melt-blown nonwoven fabric, Exxon Mobil Corp.(NYSE:XOM) removed from Dow Jones Industrial Average, and the oil demand peak theory proposed by BP Energy Outlook 2020 Edition. These events have made profound impact on petroleum exploration. Prospecting is at the forefront of petroleum industry chain, and prospectors have great influence on petroleum industry. The responsibility of petroleum prospectors is to find oil, which calls for the correct way of thinking as well as scientific and technical means, both of which are indispensable. When it comes to the cognition of petroleum exploration, we should draw lessons from predecessors' philosophy of finding oil from a development perspective. It is necessary to define the relationship between subject activity and objective structure, as there is an inherent tension between the two and a dialectical relationship that complements each other. It is also essential to illustrate the logic of initiative and decisiveness, as between the two is the dual logic of active logic that changes the world and deterministic logic based on science and technology. The strategic breakthrough in the Gulong shale oil exploration in Daqing is a typical example. Our knowledge and practice of oil exploration has overthrown the Hubbert Curve. The new curve may have more than one peak, which means hopes are always there for finding oil. Climbing to the top of a mountain must start from the foot. A journey of a thousand miles must begin with a single step. Looking forward to the future, prospectors have the wisdom, ability, and methods to find more, cleaner, and more affordable oil to drive the progress of human civilization. This is the duty of petroleum prospectors.

近年来,塔里木盆地缝洞型碳酸盐岩因持续发现超深层资源潜力而备受关注,但该类储层存在成因和特征不明确以及勘探方向缺乏有效指导等问题.基于地震资料解释,结合资料调研、野外露头考察、岩心及薄片观察、地球化学分析和生产特征分析等手段,对哈拉哈塘地区奥陶系缝洞型碳酸盐岩的岩溶类型和特征进行了深入研究.哈拉哈塘地区发育表生岩溶和热液岩溶两类岩溶储层且特征差异明显.表生岩溶储层主要发育在良里塔格组,在良里塔格组顶面形成典型的岩溶地貌,内部形成水平管状洞穴体系;洞穴发生充填、垮塌和强烈压实,导致储层较致密,储集物性相对较差.热液岩溶储层主要发育在一间房组和鹰山组上部,沿断裂发育形成竖型洞穴,该类型洞穴及其垮塌体保留大量储集空间,在地震剖面上表现为强振幅"串珠",造成频繁的放空和漏失现象,是哈拉哈塘油田奥陶系主要油气储集体.而热液岩溶储层是现阶段研究区勘探开发的主要目标,而表生岩溶储层应合理规避.

After the preliminary basic research on the problems encountered during the production period of Gulong shale oil in the Songliao Basin, NE China, and the scientific exploration, the special characteristics of Gulong shale oil in terms of reservoir space, phase distribution, flow pattern, and mineral evolution are proposed. The main results are as follows : (1) The source of organic matter, mechanism of hydrocarbon generation and expulsion, and key factors affecting shale oil abundance; (2) The types and structural characteristics of the reservoir and their contribution to porosity and permeability; (3) The mineral origin and evolution of minerals and their influence on reservoir availability, sensitivity, and compressibility; (4) The rock mechanical characteristics and fracture propagation law of Gulong shale; (5) The shale oil products, phase change law and main control factors of adsorption and desorption conversion of Gulong shale oil; (6) The mechanism of shale oil-liquid, solid-liquid gas interaction and enhanced oil recovery. Three key research suggestions are proposed to realize the large-scale economic utilization of the Gulong shale oil as follows: (1) Deepen research on the mechanism of oil and gas generation and discharge, storage and transportation, to guide the selection of geological sweet spots of shale oil; (2) Deepen research on the compressibility and fracture initiation mechanism to support the selection of engineering sweet spots and optimization of engineering design; (3) Deepen research on the fluid interaction mechanism under reservoir conditions, os us to guide the optimization of development schemes and the selection of EOR technologies. A successful development of Gulong shale oil requires global experts and scholars to contribute multidisciplinary innovative ideas and technical ideas to solve production problems.

塔里木盆地牙哈凝析气藏2000年开始采用循环注气开发技术提高凝析油采收率.但随着注气时间的延长,气油比受气窜的影响呈快速上升趋势.气藏历年的动态监测显示,注入的干气与地下凝析气并不能完全混相.室内多相流体PVT实验证实,干气与凝析气存在明显的界面,明确了驱替作用下干气和凝析气的非混相特征.基于瞬时平衡假设的相态和渗流理论无法准确描述其运动规律.熵增数学模型确定了不同储层物性特征对不同性质流体达到相平衡的影响;微元数学模型确定了重力作用对干气和凝析气渗流规律的显著作用;二维机理模型明确了3种作用力在注气井和采气井之间的作用范围.现场试验数据反映了气藏尺度的干气—凝析气运动规律,室内实验数据与数学模型分析反映了孔隙尺度和岩心尺度的开发机理,从而揭示了凝析气藏循环注气"扩散—驱替—重力分异"三元开发机理,明确了重力分异作用是影响循环注气效果的主要因素.基于循环注气三元开发机理,建立考虑扩散、重力分异与储层结构等多因素耦合的非平衡渗流数学模型,提高了循环注气开发过程中的流体分布预测精度,并建立了凝析气藏注气重力辅助立体驱替提高采收率新方法.该技术在塔里木盆地牙哈凝析气田得到了成功应用.

Through reviewing the development history of tight oil and gas in China, summarizing theoretical understandings in exploration and development, and comparing the geological conditions and development technologies objectively in China and the United States, we clarified the progress and stage of tight oil and gas exploration and development in China, and envisaged the future development orientation of theory and technology, process methods and development policy. In nearly a decade, relying on the exploration and development practice, science and technology research and management innovation, huge breakthroughs have been made. The laws of formation, distribution and accumulation of tight oil and gas have been researched, the development theories such as "multi-stage pressure drop" and "man-made reservoirs" have been established, and several technology series have been innovated and integrated. These technology series include enrichment regions selection, well pattern deployment, single well production and recovery factor enhancement, and low cost development. As a result, both of reserves and production of tight oil and gas increase rapidly. However, limited by the sedimentary environment and tectonic background, compared with North America, China's tight oil and gas reservoirs are worse in continuity, more difficult to develop and poorer in economic efficiency. Moreover, there are still some gaps in reservoir identification accuracy and stimulating technology between China and North America. In the future, Chinese oil and gas companies should further improve the resource evaluation method, tackle key technologies such as high-precision 3D seismic interpretation, man-made reservoir, and intelligent engineering, innovate theories and technologies to enhance single well production and recovery rate, and actively endeavor to get the finance and tax subsidy on tight oil and gas.