Quantitative prediction of shale gas sweet spots based on seismic data in Lower Silurian Longmaxi Formation,Weiyuan area,Sichuan Basin,SW China

Sweet spots in the shale reservoirs of the Lower Silurian Longmaxi Formation in Weiyuan 201 Block of Sichuan Basin were predicted quantitatively using seismic data and fuzzy optimization method. First, based on seismic and rock physics analysis, the rock physics characteristics of the reservoirs were determined, and elastic parameters sensitive to shale reservoirs with high gas content were selected. Second, data volumes with high precision of the elastic parameters were obtained from pre-stack simultaneous inversion. The horizontal distribution of key parameters for shale gas evaluation were calculated based on the results of rock physics analysis. Then, the fuzzy evaluation equation was established by fuzzy optimization method with test and logging data of horizontal wells with similar operation conditions. key parameters affecting the productivity of horizontal wells were sorted out and the weights of them in the sweet spots quantitative prediction were worked out by fuzzy optimization to set up a sweet spots evaluation system. Three classes of shale gas reservoirs which including two kinds of sweet spots were predicted with the above procedure, and the sweet spots have been predicted quantitatively by combining the above prediction results with the testing production. The testing results of 7 verification wells proved the reliability of the prediction results.

Prestack inversion based on anisotropic Markov random field-maximum posterior probability inversion and its application to identify shale gas sweet spots

Economic shale gas production requires hydraulic fracture stimulation to increase the formation permeability. Hydraulic fracturing strongly depends on geomechanical parameters such as Young＇s modulus and Poisson＇s ratio. Fracture-prone sweet spots can be predicted by prestack inversion, which is an ill-posed problem; thus, regularization is needed to obtain unique and stable solutions. To characterize gas-bearing shale sedimentary bodies, elastic parameter variations are regarded as an anisotropic Markov random field. Bayesian statistics are adopted for transforming prestack inversion to the maximum posterior probability. Two energy functions for the lateral and vertical directions are used to describe the distribution, and the expectation-maximization algorithm is used to estimate the hyperparameters of the prior probability of elastic parameters. Finally, the inversion yields clear geological boundaries, high vertical resolution, and reasonable lateral continuity using the conjugate gradient method to minimize the objective function. Antinoise and imaging ability of the method were tested using synthetic and real data.

Key geological factors governing sweet spots in the Wufeng-Longmaxi shales of the Sichuan Basin,China

Production performance of the Wufeng-Longmaxi shales varies significantly among Fuling,Weirong,and Wulong fields in the Sichuan Basin.Total organic carbon(TOC)content,mineralogy,and organic matter(OM)pore characteristics are investigated to identify key factors governing sweet spots.Siliceous shales with good preservation conditions in the Fuling Field exhibit large thickness,high TOC content and thin-section porosity(TSP),and well-developed OM macropores,thus high initial production and estimated ultimate recovery(EUR).Thin carbonate-containing siliceous shales with good preservation conditions in the Weirong Field feature medium-to-high TOC and well-developed OM macropores but low TSP,leading to high initial production but low EUR.Siliceous shales with poor preservation conditions in the Wulong Field are characterized by large thickness,high TOC,low TSP and poorly-developed OM macropores,causing low initial production and EUR.Both sedimentary and preservation conditions are intrinsic decisive factors of sweet spots,as they control the mineral composition,TOC,and OM macropore development.Deep-water shales in transgressive systems tracts(TSTs)exhibit better-developed OM macropores and greater TOC compared to highstand systems tracts(HSTs).OM macropores are most prevalent in siliceous shales,followed by carbonate-containing siliceous shales and then argillaceous shales.Furthermore,good preservation conditions are conducive to retain OM macropores with low pore aspect ratio(PAR).Comparison among the three fields shows that high-TOC silicious shales with good preservation conditions are the highest in TSP and EUR.Therefore,organic richness,lithofacies,and preservation conditions are the major factors which determine OM pore development,governing the sweet spots of the Wufeng-Longmaxi shales.

Evaluation of sweet spots and horizontal-well-design technology for shale gas in the basin-margin transition zone of southeastern Chongqing,SW China

The shale gas accumulation conditions in the basin-margin transition zone of southeastern Chongqing in SW China are complex.In order to improve single-well productivity in this area,the geologic characteristics,major factors controlling the occurrence of sweet spots,and drilling/fracturing optimization were investigated in this study.The sweet spot evaluation system and criteria were established,and the horizontal-well-design technology was developed.The following three conclusions were drawn.First,the accumulation and high-productivity-oriented approaches for sweet spot evaluation are proposed and the criteria are established based on screened key indicators.Second,the horizontal well was designed based on:(1)the“six-map”method,to identify both the geology and engineering sweet spots for well locations;and(2)seismic attributes,to predict the development of fractures and cavities,and thus,avoid mud loss and improve the drilling efficiency.The target window,well-azimuth optimization,and the curvature were forecasted to improve the fracturing performances.Third,the Pingqiao anticline,Dongsheng anticline,Jinfo slope,and Wulong syncline were selected as Type I sweet spots.Currently,shale gas has been successfully discovered in the basin-margin transition zone and is being commercially developed.

Comprehensive Evaluation of Geological and Engineering Sweet Spots of Shale Gas Reservoir: A Case Study of the Luzhou Block, Sichuan Basin

There is a huge amount of marine shale gas resources in the southern Sichuan Basin in China, and most of the resources are at the buried depth of 3500 - 4500 meters. At present, deep shale gas is in the early stage of exploration and development. In order to achieve large-scale efficient development, in addition to optimizing favorable blocks, it is also to identify the optimal target in the vertical direction combine geology, drilling, and fracturing. Therefore, Taking the Longmaxi formation shale in the Luzhou block as the research object, based on drilling, logging, and core experiment data, through single well and 3D geomechanical modeling methods, analyze the characteristics of organic matter abundance, porosity, pore pressure, collapse pressure, mineral composition and in-situ stress of different layers of shale in Longmaxi formation. Systematically summarized the main controlling factors of the “sweet spot” of deep shale gas and establish the comprehensive evaluation system of deep shale gas “sweet spots”, to clarify the optimal “sweet spots” of geology, drilling, and fracturing in the Longmaxi reservoir. Results show that the total organic carbon content, porosity, and gas saturation of the long111 layer are higher than other layers. The Long111 layer has a low collapse pressure and a high compressive strength, the risk of wellbore instability is relatively low. The stress difference coefficient of All layers is less than 0.3, and the brittleness index of the Long111 layer is 62.35%. A complex fracture network is easier to form after fracturing. The conclusion shows that the Long111 layer is the optimal reservoir section of the Longmaxi Formation. Ensure the drilled rate of the Long111 layer and maximize the length of the horizontal section can obtain higher production.

A systematic step-wise approach for shale gas assessment in undeveloped prospects:A case study of Lurestan shale gas area in Iran

Key parameters and evaluation methods of shale gas show that it is not possible to guarantee the commercial and economic development of shale gas by sorting out geological sweet spots only according to technical indicators.A research method combining technical indicators including total organic carbon content and vitrinite reflectance with economic indicators including internal rate of return and investment payback period is proposed to screen the best technological and economic development sweet spots in undeveloped areas.This method was used to evaluate the best technological and economic development sweet spots in Cretaceous shale gas reservoirs S_(1) and S_(2) of Lurestan area,Iran.Twenty-one geologic sweet spots were picked out based on effective reservoir thickness,vitrinite reflectance and gas content.Based on analogy method,the pressure gradient,clay mineral content,buried depth and other parameters were taken as comparative indicators,the Eagle Ford shale as comparison object,recovery factor and production curve were extracted to estimate the technologically recoverable reserves of the study area.On this basis,the economic indexes such as internal rate of return and investment payback period were used to evaluate the economy of the geological sweet spots.In the case of P_(10) distribution,the total technologically recoverable reserves and economically recoverable reserves are 7875×10^(8)m^(3) and 4306×10^(8)m^(3) respectively,11 geological sweet spots have commercial development value,among which,No.1 sweet spot has the highest value,with a net present value of 35×10^(8) USD.

Types and genesis of sweet spots in the tight sandstone gas reservoirs:Insights from the Xujiahe Formation,northern Sichuan Basin,China

Through comprehensively applying geological and geophysical data,as well as core and thin section observation,the characteristics of reservoirs and fractures in the second member of the Xujiahe Formation(hereinafter referred to as Xu2 Member)in the Yuanba area,northern Sichuan Basin,were studied.Combined with the analysis of the main controlling factors of production capacity,the types and characteristics of the sweet spots in the tight sandstone gas reservoir were determined.The evaluation standards and geological models of the sweet spots were established.The results are as follows:(1)There are bedding-parallel fracture-,fault-induced fracture-,and pore-dominated sweet spots in the tight sandstone gas reservoirs of the Xu2 Member.(2)The bedding parallel fracture-dominated sweet spots have developed in quartz sandstones with well-developed horizontal fractures and micro-fractures.They are characterized by high permeability and high gas output during production tests.This kind of sweet spots is thin and shows a limited distribution.Their logging responses show extremely low gamma-ray(GR)values and medium-high AC values.Moreover,the bedding parallel fracture-dominated sweet spots can be mapped using seismic methods.(3)The fault-induced fracture-dominated sweet spots have welldeveloped medium-and high-angle shear fractures.Their logging responses show an increase in peaks of AC values and total hydrocarbon content and a decrease in resistivity.Seismically,the areas with welldeveloped fault-induced fracture-dominated sweet spots can be effectively mapped using the properties such as seismic entropy and maximum likelihood.(4)The pore-dominated sweet spots are developed in medium-grained feldspathic litharenites with good reservoir properties.They are thick and widely distributed.(5)These three types of sweet spots are mainly determined by sedimentation,diagenesis,and tectonism.The bedding parallel fracture-dominated sweet spots are distributed in beachbar quartz sandstones on the top of the 1st sand layer group in the Xu2 Member,which develops in a shore-shallow lake environment.The fault-induced fracture-dominated sweet spots mainly occur near faults.They are increasingly developed in areas closer to faults.The pore-dominated sweet spots are primarily distributed in the 2nd and 3rd sand layer groups,which lie in the development areas of distributary channels near provenances at western Yuanba area.Based on the geological and seismic data,a comprehensive evaluation standard for these three types of sweet spots of the tight sandstone reservoirs in the Xu2 Member has been established,which,on the one hand,lays the foundation for the development and evaluation of the gas reservoir,and on the other hand,deepens the understanding of sweet spot in the tight sandstone gas reservoirs.

Geological characteristics and ‘‘sweet area'' evaluation for tight oil

Tight oil has become the focus in exploration and development of unconventional oil in the world, especially in North America and China. In North America, there has been intensive exploration for tight oil in marine. In China, commercial exploration for tight oil in conti- nental sediments is now steadily underway. With the dis- covery of China＇s first tight oil field--Xin＇anbian Oilfield in the Ordos Basin, tight oil has been integrated officially into the category for reserves evaluation. Geologically, tight oil is characterized by distribution in depressions and slopes of basins, extensive, mature, and high-quality source rocks, large-scale reservoir space with micro- and nanopore throat systems, source rocks and reservoirs in close contact and with continuous distribution, and local ＂sweet area.＂ The evaluation of the distribution of tight oil ＂sweet area＂ should focus on relationships between ＂six features.＂ These are source properties, lithology, physical properties, brittleness, hydrocarbon potential, and stress anisotropy. In North America, tight oil prospects are distributed in lamellar shale or marl, where natural fractures are fre- quently present, with TOC 〉 4 %, porosity 〉 7 %, brittle mineral content 〉 50 %, oil saturation of 50 %-80 %, API 〉 35~, and pressure coefficient 〉 1.30. In China, tight oil prospects are distributed in lamellar shale, tight sand- stone, or tight carbonate rocks, with TOC 〉 2 %, poros- ity 〉 8 %, brittle mineral content 〉 40 %, oil saturation of 60 %-90 %, low crude oil viscosity, or high formation pressure. Continental tight oil is pervasive in China and its preliminary estimated technically recoverable resources are about （20-25） × lO8^ t.

China's shale gas exploration and development: Understanding and practice

Through detailed analyses of the distribution characteristics of organic-rich shale, appearance features of high-quality shale, microscopic characteristics of shale reservoir rocks, fracability, and the relationship between preservation conditions and shale gas enrichment in Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Sichuan Basin, theoretical understandings and specific suggestions with respect to the exploration and development of shale gas in China are summarized and proposed respectively. Important geological understandings in the exploration and development of shale gas of the Wufeng Formation–Longmaxi Formation in the Sichuan Basin can be summarized into the following aspects: depositional environment and depositional process control the distribution of organic-rich shale; high quality shale in "sweet spot segments" are commonly characterized by high content of organic carbon, high brittleness, high porosity and gas content; organic pores are important storage space for the enrichment of shale gas; preservation conditions are the key factor for the geological evaluation of shale gas in structurally complex regions; shale gas can be considered as "artificial gas reservoirs" and the fracability assessment is essential for high-production; nanoscale storage space and the mode of occurrence control the special seepage characteristics of shale gas. The following suggestions are proposed for the development of China's shale gas industry:(1) focus more on fundamental research to achieve new breakthrough in the geological theory of shale gas;(2) emphasize exploration practices to have all-round discoveries in multiple strata;(3) study the regularities of development and production to establish new models of shale gas development;(4) think creatively to invent new technologies to tackle key problems;(5) explore the management innovation to create new mechanisms in shale gas development.

Key geological factors controlling the estimated ultimate recovery of shale oil and gas: A case study of the Eagle Ford shale, Gulf Coast Basin, USA

Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate recovery(EUR) of shale oil and gas of the wells are predicted by using two classical EUR estimation models, and the average values predicted excluding the effect of engineering factors are taken as the final EUR. Key geological factors controlling EUR of shale oil and gas are fully investigated. The reservoir capacity, resources, flow capacity and fracability are the four key geological parameters controlling EUR. The storage capacity of shale oil and gas is directly controlled by total porosity and hydrocarbon-bearing porosity, and indirectly controlled by total organic carbon(TOC) and vitrinite reflectance(Ro). The resources of shale oil and gas are controlled by hydrocarbon-bearing porosity and effective shale thickness etc. The flow capacity of shale oil and gas is controlled by effective permeability, crude oil density, gas-oil ratio, condensate oil-gas ratio, formation pressure gradient, and Ro. The fracability of shale is directly controlled by brittleness index, and indirectly controlled by clay content in volume. EUR of shale oil and gas is controlled by six geological parameters: it is positively correlated with effective shale thickness, TOC and fracture porosity, negatively correlated with clay content in volume, and increases firstly and then decreases with the rise of Ro and formation pressure gradient. Under the present upper limit of horizontal well fracturing effective thickness of 65 m and the lower limit of EUR of 3×10^(4) m^(3), when TOC<2.3%, or Ro<0.85%, or clay content in volume larger than 25%, and fractures and micro-fractures aren’t developed, favorable areas of shale oil and gas hardly occur.

Multi-source genesis of continental carbonate-rich fine-grained sedimentary rocks and hydrocarbon sweet spots

This paper systematically discusses the multiple source characteristics and formation mechanisms of carbonate-rich fine-grained sedimentary rocks through the analysis of material source and rock formation.The hydrocarbon accumulation characteristics of carbonate-rich fine-grained sedimentary rocks are also summarized.The results show that the main reason for the enrichment of fine-grained carbonate materials in rift lake basins was the supply of multiple material sources,including terrestrial material input,formation of intrabasinal authigenic carbonate,volcanic-hydrothermal material feeding and mixed source.The development of carbonate bedrock in the provenance area controlled the filling scale of carbonate materials in rift lake basins.The volcanic-hydrothermal activity might provide an alkaline fluid to the lake basins to strengthen the material supply for the formation of carbonate crystals.Authigenic carbonate crystals induced by biological processes were the main source of long-term accumulation of fine-grained carbonate materials in the lake basins.Carbonate-rich fine-grained sedimentary rocks with multiple features were formed through the interaction of physical,biochemical and chemical processes during the deposition and post-deposition stages.The source and sedimentary origin of the fine-grained carbonate rock controlled the hydrocarbon accumulation in it.In the multi-source system,the types of"sweet spots"of continental shale oil and gas include endogenous type,terrigenous type,volcanic-hydrothermal type and mixed source type.

Production characteristics and sweet-spots mapping of the Upper Devonian-Lower Mississippian Bakken Formation tight oil in southeastern Saskatchewan, Canada

A workflow that helps identify potential production sweet spots in the Middle Bakken tight oil play is proposed based on analysis of large amounts of production data. The proposed approach is a multivariate statistical model that extracts relevant information from a training dataset of production wells to facilitate geological similarity comparison between economic and sub-economic production wells. The model is applied to the Middle Bakken tight oil play in southeastern Saskatchewan. Data screening for diagnostic geological indicators for sweet spots reveals that several geological factors indicative for conventional oil reservoirs seem to work for the Middle Bakken tight oil play as well. These factors include: a) the NE Torqunay-Rocanville Trend serving as a preferred regional migration path for connecting mature source rock in southern Williston Basin and the Middle Bakken tight reservoir in southeastern Saskatchewan; b) the oils in the Bakken tight reservoirs along the U.S. and Canada border are more likely from local matured Bakken source rocks; c) subtle structural components enhancing the convergence of dispersed hydrocarbons over a large area; d) top seal and lateral barrier improving preservation, thus favouring oil productivity; e) orientation of maximum horizontal stress coincident with the direction of the variogram spatial continuity in ultimate recoverable reserves, so the direction of horizontal well has a significant impact on the oil productivity.

“Exploring petroleum inside source kitchen”: Connotation and prospects of source rock oil and gas

Based on the transitional background of the global energy structure, exploration and development of unconventional oil and gas, and investigation of key basins, the unconventional oil and gas resources are divided into three types: source rock oil and gas, tight oil and gas, and retention and accumulated oil and gas. Source rock oil and gas resources are the global strategic supplies of oil and gas, the key resource components in the second 150-year life cycle of the future petroleum industry, and the primary targets for "exploring petroleum inside source kitchen". The geological connotation of source rock oil and gas was proposed, and the models of source rock oil and gas generation, expulsion and accumulation were built, and five source rock oil and gas generation sections were identified, which may determine the actual resource potential under available technical conditions. The formation mechanism of the "sweet sections" was investigated, that is, shale oil is mainly accumulated in the shale section that is close to the oil generation section and has higher porosity and permeability, while the "sweet sections" of coal-bed methane(CBM) and shale gas have self-contained source and reservoir and they are absorbed in coal seams or retained in the organic-rich black shale section, so evaluation and selection of good "sweet areas(sections)" is the key to "exploring petroleum inside source kitchen". Source rock oil and gas resources have a great potential and will experience a substantial growth for over ten world-class large "coexistence basins" of conventional-unconventional oil and gas in the future following North America, and also will be the primary contributor to oil stable development and the growth point of natural gas production in China, with expected contribution of 15% and 30% to oil and gas, respectively, in 2030. Challenges in source rock oil and gas development should be paid more attention to, theoretical innovation is strongly recommended, and a development pilot zone can be established to strengthen technology and promote national support. The source rock oil and gas geology is the latest progress of the "source control theory" at the stage of unconventional oil and gas. It will provide a new theoretical basis for the new journey of the upstream business in the post-industry age.

Development potential and technical strategy of continental shale oil in China

Continental shale oil is a general term for liquid hydrocarbons and many kinds of organic matter in continental organic-rich shale series with vitrinite reflectance of more than 0.5%at buried depth of more than 300 m,and is an important type of source-rock oil and gas.Based on the evolution model of oil generation and expulsion in organic-rich shale series controlled by maturity,continental shale oil is divided into two types:medium-high maturity and medium-low maturity.(1)The continental shale series in China develop high-quality source rocks of freshwater and saltwater lacustrine facies,as well as multiple types of reservoirs,including clastic rocks,carbonate rocks,diamictite,tuff and shale,forming a number of"sweet sections"and"sweet areas"of continuous distribution inside or near source rocks,which have large scale resources.(2)Experimental analysis of organic rich shale samples shows that the shale samples with wavy and horizontal beddings have good storage conditions,and the horizontal permeability of shale is tens to hundreds of times of its vertical permeability,which is conducive to the lateral migration and accumulation of shale oil in the source rocks.(3)After evaluation,the geological resources of medium-high maturity shale oil are about 10 billion tons,which can be effectively developed by horizontal drilling and volumetric fracturing,and will be a practical field of oil exploration in recent years.Shale oil with medium and low maturity has huge resource potential,and technological recoverable resources of(70?90)billion tons,making it a strategic alternative resource of oil industry.However,economic development of this type of shale oil needs in-situ conversion technology breakthroughs.Continental shale oil is an inevitable choice in the process of Chinese continental petroleum exploration from"outside source"to"inside source".Making breakthroughs in the core technologies such as"sweet area"evaluation and optimization,horizontal well volume fracturing and in-situ conversion technology and equipment is the key to realizing scale development of continental shale oil economically.

中国页岩气特征、挑战及前景(一)

基于近年中国富有机质页岩沉积模式、页岩储集层表征等方面取得的研究进展,分析页岩气富集高产主控因素。研究落实了上奥陶统五峰组—下志留统龙马溪组笔石带发育序列时空对比依据,提出缓慢沉降的稳定海盆、高海平面、半封闭水体和低沉积速率是海相富有机质页岩重要沉积模式,确定晚奥陶世—早志留世早期持续发育的大型深水陆棚沉积环境有利于黑色页岩发育,优质页岩厚20~80 m、TOC值为2.0%~8.4%。对比分析焦石坝、长宁、威远3大页岩气田,指出规模储集层主要受富生物硅质与钙质页岩、适中热演化程度、高基质孔隙与丰富的裂缝控制。五峰组—龙马溪组总孔隙度为3.0%~8.4%、渗透率为0.000 2×10-3~0.500 0×10-3μm2,基质孔隙体积及其构成区域稳定,裂缝孔隙发育特征在不同构造区、同一构造的不同井区和不同层段差异较大。筇竹寺组受有机质炭化、黏土矿物结晶度高和生物碎屑粒内孔后期充填等因素影响,物性普遍较差,总孔隙度为1.5%~2.9%、渗透率为0.001′10-3~0.010′10-3μm2。明确了页岩气富集高产受沉积环境、热演化程度、孔缝发育程度、构造保存等＂四大因素＂控制,且特殊性在于高演化（Ro值：2.0%~3.5%）、超高压（压力系数：1.3~2.1）,从而建立了＂构造型甜点＂和＂连续型甜点区＂两种页岩气富集模式。

中国陆相页岩油发展潜力与技术对策

陆相页岩油是埋藏300 m以深、Ro值大于0.5%的陆相富有机质页岩层系中赋存的液态烃和各类有机物的统称,是源岩油气的重要组成类型。以成熟度控制富有机质页岩生排油演化模式为依据,将陆相页岩油划分为中高成熟度和中低成熟度两种类型,研究发现中国陆相页岩层系:①发育淡水和咸水两类湖相优质烃源岩,存在碎屑岩、碳酸盐岩、混积岩、沉凝灰岩、泥页岩等多种类型储集层,形成多套近源或源内聚集的“甜点段”和大面积分布的“甜点区”,具规模资源基础。②富有机质页岩实验分析表明,波状和水平纹层状页岩具良好储集条件,页岩水平渗透率是垂向渗透率的数十倍—数百倍,利于源内页岩油横向规模运聚。③经评价,中高成熟度页岩油地质资源总量超过100×10^8 t,采用水平井体积压裂技术可以有效开发,是近期石油勘探现实领域;中低成熟度页岩油资源潜力大,初步评价技术可采资源量为(700~900)×10^8 t,是未来石油工业发展的战略性接替资源,需要原位转化等技术突破才能实现效益开发。陆相页岩油是中国陆上油气勘探从“源外”走向“源内”的必然选择,突破“甜点区”评价优选、水平井体积压裂工程技术以及原位转化技术装备等核心理论技术,是实现陆相页岩油规模效益发展的重要途径。

“进源找油”:致密油主要类型及地质工程一体化进展

致密油是国内"进源找油"的主要对象,地质工程一体化是实现中国致密油规模效益发展的必由之路。文章提到的致密油,等同于页岩层系石油,是指依靠水平井体积压裂等现有技术可以实现规模效益开发的陆相非常规石油资源,致密油"进源找油"包括找出"甜点区"和采出"甜点体"两个内涵,根据页岩层系储层岩性、源储组合差异,将中国陆上致密油划分为"碎屑岩、混积岩—沉凝灰岩、碳酸盐岩"3种主要类型。致密油地质工程一体化,就是以"甜点区(段)"评价识别为基础,以"甜点体"高产稳产为目标,以"逆向思维设计、正向作业施工"为工作指南,坚持地质设计与工程实践一体化组织管理,做好"甜点区(段)"评价刻画和"人工油藏"制造开发两篇文章,最终把蓝图设计转化为工程作业、转化为效益产量的系统工业过程。以松辽盆地扶余油层碎屑岩、柴西南扎哈泉碎屑岩、吉木萨尔凹陷芦草沟组混积岩、马朗凹陷条湖组沉凝灰岩、柴西南英西地区下干柴沟组碳酸盐岩、川中北大安寨段页岩等不同类型致密油为例,分类型阐述了中国石油探区研究区致密油地质工程一体化在地质评价预测、工程关键技术和主要管理举措等3个方面的研究进展,"十三五"前3年新增三级储量9.97×108t,新建产能225×104t,取得了油气发现和产能建设"双丰收"。最后初步提出依托致密油地质工程一体化发展,加强多层系立体"人工油藏"开发、建立不同类型小区块"参考模板"、高度关注页岩层系源岩油气等建议。

“进源找油”:论四川盆地非常规陆相大型页岩油气田

源岩油气规模快速发展,是中国能源结构转型的重要战略选项;陆相页岩油和气是中国源岩油气最具潜力的组成类型,是中国陆上未来"进源找油"最重要的突破对象。本文首次研判提出四川盆地侏罗系油和气发展,应尽快由常规构造-裂缝石油、致密灰岩与砂岩油向孔隙型页岩油气转变,重点阐述了大安寨段页岩油气4项新进展:①评价侏罗系4套富有机质页岩总生油量245×10^8t,石油总资源量172×10^8t,还有相当规模的天然气资源,既富油又富气,其中67%的油气资源集中在大安寨段;②大安寨段二亚段是侏罗系页岩油和气的"甜点段",黑色页岩厚度一般20~80m,TOC平均值大于2%,Ⅱ1~Ⅱ2型干酪根,Ro主体1.1%~1.4%,处于轻质油-凝析油气窗口,页岩储层孔隙度4%~6%,页理裂缝发育,脆性矿物含量一般在50%以上,压力系数1.2~1.8,滞留烃量多为100~200mg/g·TOC,油质较轻,地层埋深较浅,具备与北美页岩油气媲美的地质工程条件;③优选出页岩油气"甜点区"评价的3项核心参数(Ro、富有机质页岩厚度、埋藏深度),评价出大安寨段二亚段页岩油"甜点区"主要分布在盆地中北部地区,页岩厚度20~50m,面积约2×104km2;④提出了加快页岩油和气以水平井体积压裂为核心的风险勘探和开发试验、加强全层系资源评价、加速准备先导试验技术方案等建议,力争推动侏罗系孔隙型页岩油和气突破发现。四川盆地侏罗系陆相页岩油和气新认识,可能为真正开启侏罗系源岩油气"进源找油"、规模开发新征程提供重要的理论依据。

松辽盆地古龙页岩油甜点特征及分布

松辽盆地北部页岩油资源丰富,落实甜点资源、空间分布及富集因素意义重大。利用宏观岩心精细描述、微观实验分析,开展了古龙页岩油甜点储集性、含油性、流动性、可压性研究。在“四性”评价基础上,初步分析了影响甜点的主控因素。结果表明:古龙页岩油具有储集性能好、含油丰富、地层压力高、原油密度低、原油黏度小、较高的气油比等特点;高有机质层状和纹层状页岩发育、高成熟热演化和较高的地层压力是古龙页岩油富集高产的主要控制因素。纵向上,甜点层主要发育在青一段及青二段下部,根据岩相组合类型、含油特征可分为上、中、下3个甜点段,其中下甜点段发育优质甜点层,横向分布稳定。平面上,甜点区主要分布在齐家—古龙地区。目前齐家—古龙地区下甜点段试油已得到证实,是勘探开发最有利目标区和甜点靶层。

常规-非常规油气“有序聚集”理论认识及实践意义

在分析全球常规．非常规油气发展态势、梳理中国近10年油气地质理论与技术创新成果基础上，系统阐述了常规．非常规油气“有序聚集”内涵，指出常规油气供烃方向有非常规油气共生、非常规油气外围空间可能有常规油气伴生，强调常规油气与非常规油气协同发展，找油思想从“源外找油”深入到“进源找油”。非常规油气甜点着眼于烃源性、岩性、物性、脆性、含油气性与应力各向异性“六特性”匹配评价，以页岩气为例，中国有利页岩气TOC大于2％，纹层状硅质钙质或钙质硅质页岩，孔隙度3％～8％，脆性矿物含量50％~80％，含气量2．3～4．1m0／t，压力系数1．0～2．3，天然裂缝发育；北美有利页岩气TOC大于4％，硅质页岩、钙质页岩或泥灰岩，孔隙度4％～9％，脆性矿物含量40％-70％，含气量2．8～9．9m3／t，压力系数1．30～1.85，天然裂缝发育。重点论述了“甜点区”评价、平台式“工厂化”生产模式等方法与技术：提出非常规油气富集“甜点区”8项评价标准，其中3项关键指标是TOC大于2％（其中页岩油蜀大于2mg／g）、孔隙度较高（致密油气大于10％，页岩油气大于3％）和微裂缝发育；阐述了多井平台式“工厂化”生产内涵及其实施需要具备“批量布井、标准设计、流水作业、重复利用”4要素；通过地下含油气地层各方向水平井体积压裂，形成大型人工缝网系统“人造油气藏”。