Numerical evaluations on the fluid production in the in-situ conversion of continental shale oil reservoirs

In-situ conversion presents a promising technique for exploiting continental oil shale formations,characterized by highly fractured organic-rich rock.A 3D in-situ conversion model,which incorporates a discrete fracture network,is developed using a self-developed thermal-flow-chemical(TFC)simulator.Analysis of the model elucidates the in-situ conversion process in three stages and defines the transformation of fluids into three distinct outcomes according to their end stages.The findings indicate that kerogen decomposition increases fluid pressure,activating fractures and subsequently enhancing permeability.A comprehensive analysis of activated fracture permeability and heating power reveals four distinct production modes,highlighting that increasing heating power correlates with higher cumulative fluid production.Activated fractures,with heightened permeability,facilitate the mobility of heavy oil toward production wells but hinder its cracking,thereby limiting light hydrocarbon production.Additionally,energy efficiency research demonstrates the feasibility of the in-situ conversion in terms of energy utilization,especially when considering the surplus energy from high-fluctuation energy sources such as wind and solar power to provide heating.

Development review and the prospect of oil shale in-situ catalysis conversion technology

As an unconventional resource, oil shale possesses abundant reserves and significant potential for industrial applications. The rational and efficient development of oil shale resources holds immense importance in reducing national energy demand. In-situ catalytic technology, characterized by its high efficiency, low pollution, and minimal energy consumption, represents a key direction for future oil shale development. This paper provides a comprehensive review of research progress in in-situ oil shale mining technology, oil shale pyrolysis catalysts, the pyrolysis mechanism of kerogen, and the compatibility of different heating processes and catalysts. Furthermore, the paper proposes future research directions and prospects for oil shale in-situ catalytic technology, including reservoir modification, highefficiency catalyst synthesis, injection processes, and high-efficiency heating technology. These insights serve as valuable technical references for the advancement of oil shale in-situ catalytic technology.

Assessment of recoverable oil and gas resources by in-situ conversion of shale——Case study of extracting the Chang 7_(3) shale in the Ordos Basin

The purpose of this study is to investigate the entire evolution process of shales with various total organic contents(TOC)in order to build models for quantitative evaluation of oil and gas yields and establish methods for assessing recoverable oil and gas resources from in-situ conversion of organic matters in shale.Thermal simulation experiments under in-situ conversion conditions were conducted on Chang 7_(3) shales from the Ordos Basin in a semi-open system with large capacity.The results showed that TOC and R_(o) were the key factors affecting the in-situ transformation potential of shale.The remaining oil and gas yields increased linearly with TOC but inconsistently with R_(o).R_(o) ranged 0.75%—1.25%and 1.05%—2.3%,respectively,corresponding to the main oil generation stage and gas generation stage of shale in-situ transformation.Thus a model to evaluate the remaining oil/gas yield with TOC and R_(o) was obtained.The TOC of shale suitable for in-situ conversion should be greater than 6%,whereas its R_(o) should be less than 1.0%.Shales with 0.75%(R_(o))could obtain the best economic benefit.The results provided a theoretical basis and evaluation methodology for predicting the hydrocarbon resources from in-situ conversion of shale and for the identification of the optimum“sweet spots”.The assessment of the Chang 7_(3) shale in the Ordos Basin indicated that the recoverable oil and gas resources from in-situ conversion of organic matters in shale are substantial,with oil and gas resources reaching approximately 450×10^(8) t and 30×10^(12)m^(3),respectively,from an area of 4.27×10^(4) km^(2).

Mechanism and reservoir simulation study of the autothermic pyrolysis in-situ conversion process for oil shale recovery

The autothermic pyrolysis in-situ conversion process (ATS) consumes latent heat of residual organic matter after kerogen pyrolysis by oxidation reaction, and it has the advantages of low development cost and exploitation of deep oil shale resources. However, the heating mechanism and the characteristic of different reaction zones are still unclear. In this study, an ATS numerical simulation model was proposed for the development of oil shale, which considers the pyrolysis of kerogen, high-temperature oxidation, and low-temperature oxidation. Based on the above model, the mechanism of the ATS was analyzed and the effects of preheating temperature, O_(2) content, and injection rate on recovery factor and energy efficiency were studied. The results showed that the ATS in the formation can be divided into five characteristic zones by evolution of the oil and O_(2) distribution, and the solid organic matter, including residue zone, autothermic zone, pyrolysis zone, preheating zone, and original zone. Energy efficiency was much higher for the ATS than for the high-temperature nitrogen injection in-situ conversion process (HNICP). There is a threshold value of the preheating temperature, the oil content, and the injection rate during the ATS, which is 400 °C, 0.18, and 1100 m3/day, respectively, in this study.

Connotation and strategic role of in-situ conversion processing of shale oil underground in the onshore China

In-situ conversion processing (ICP) of shale oil underground at the depth ranging from 300 m to 3 000 m is a physical and chemical process caused by using horizontal drilling and electric heating technology, which converts heavy oil, bitumen and various organic matter into light oil and gas in a large scale, which can be called"underground refinery". ICP has several advantages as in CO2capture, recoverable resource potential and the quality of hydrocarbon output. Based on the geothermal evolution mechanism of organic materials established by Tissot et al., this study reveals that in the nonmarine organic-rich shale sequence, the amount of liquid hydrocarbon maintaining in the shale is as high as 25%in the liquid hydrocarbon window stage (R o less than 1.0%), and the unconverted organic materials (low mature-immature organic materials) in the shale interval can reach 40%to 100%. The conditions of organic-rich shale suitable for underground in-situ conversion of shale oil should be satisfied in the following aspects, TOC higher than 6%, R o ranging between 0.5%and 1%, concentrated thickness of organic-rich shale greater than 15 meters, burial depth less than 3 000 m, covering area bigger than 50 km2, good sealing condition in both up-and down-contacting sequences and water content smaller than 5%, etc. The shale oil resource in China’s onshore region is huge. It is estimated with this paper that the technical recoverable resource reaches 70-90 billion tons of oil and 60-65 trillion cubic meters of gas. The ICP of shale oil underground is believed to be a fairway to find big oil in the source kitchen in the near future. And it is also believed to be a milestone to keep China long-term stability of oil and gas sufficient supply by putting ICP of shale oil underground into real practice in the future.

Kinetic simulation of hydrocarbon generation and its application to in-situ conversion of shale oil

The kinetic parameters of hydrocarbon generation are determined through experimental simulation and mathematical calculation using four typical samples selected from the Cretaceous Nenjiang Formation in the northwest of Songliao Basin,Chang 7 Member of Triassic Yanchang Formation in the southwest of Ordos Basin,Paleogene in the southwest of Qaidam Basin,and Lucaogou Formation of Jimusar Sag in the east of Junggar Basin.The results show that activation energy of hydrocarbon generation of organic matter is closely related to maturity and mainly ranges between 197 kJ/mol and 227 kJ/mol.On this basis,the temperature required for organic matter in shale to convert into oil was calculated.The ideal heating temperature is between 270℃and 300℃,and the conversation rate can reach 90%after 50-300 days of heating at constant temperature.When the temperature rises at a constant rate,the temperature corresponding to the major hydrocarbon generation period ranges from 225 to 350℃at the temperature rise rate of 1-150℃/month.In order to obtain higher economic benefits,it is suggested to adopt higher temperature rise rate(60-150℃/month).The more reliable kinetic parameters obtained can provide a basis for designing more reasonable scheme of in-situ heating conversion.

Heat Dissipation Modeling of <i>In-Situ</i>Conversion Process of Oil Shale

In-situ conversion of process of oil shale has been technically proven as a pilot field project. Gradually heating the reservoir by using subsurface electric heaters converts the oil shale reservoir kerogen into oil, gas and other producible components. This process also enhances the internal energy of the porous media as well as the subsurface fluid. Heat is transmitted in the reservoir within each fluid by different processes i.e. , due to the flow of fluid called advective process, and due to molecular diffusion where dispersive and diffusive processes take place. Heat transfer through conduction and convection mechanisms in the porous media are modeled mathematically and numerically incorporating the advective, dispersive and diffusive processes in the reservoir. The results show the production of oil and gas as a result of conversion of kerogen due to modeled heat dissipation.

Numerical simulation of oil shale in-situ mining using fluid-thermo-solid coupling

For the in-situ gas-injection mining technology of oil shale by process,a numerical simulation method with flow-thermo-solid coupling is proposed in this paper.This method adopts separate simulations and step-by-step coupling simulation ideas combined with the advantages of the finite element method and the finite volume method.The numerical simulation of flow-thermo-solid coupling is decomposed into two parts:flow-solid coupling and thermo-solid coupling.Considering the Fuyu oil shale in-situ production test area in Songliao Basin as an example,it is concluded that the oil shale has undergone four heating stages:a rapid temperature rise,a steady temperature rise,a slow temperature rise,and heat preservation.It takes about 10 years for the stress-strain state of the oil shale layer to reach a steady-state through the thermo-solid coupling.The main strain zones of the oil shale layer are distributed near the fracturing fractures connected to the gas injection well and at the edge of the fracturing fractures.The areas with the plastic deformation in the oil shale layer predominantly appear near the gas injection wells,production wells,and fracturing channels.The areas with the largest fracture strength are mostly distributed near the edge of the fracturing fractures with low flow velocity and low temperature.

The genetic environmental transformation mechanism of coal and oil shale deposits in eastern China’s continental fault basins and the developmental characteristics of the area’s symbiotic assemblages——taking Huangxian Basin as an example

Coal and oil shale are two common sedimentary energy sources which are often symbiotically developed in M esozoic- Cenozoic continental fault basins. However, the mechanisms and characteristics of the symbiotic development are not yet clearly known. In this research study, the typical continental fault basins of eastern China were chosen as examples for the purpose of conducting an examination of the coal and oil shale symbiotic assemblage types, genetic environmental differences, and transformation mechanisms, as well as the development and occurrence characteristics o f different assemblage types. Through a large number of investigations, systematic experimental testing, and sequence stratigraphy studies, the following conclusions were obtained:(1) There were five types of coal and oil shale symbiotic assemblages observed in the continental fault basins,(2) The development of coal and oil shale deposits requires a warm and humid climate, stable structure, abundant organic matter supply, a certain water depth, and a lower terrestrial source debris supply. The observed differences were that the water depth conditions were diversified in the study area, as well as the sources, types, and content of the organic matter.(3) The rapid transformations of the coal and oil shale genetic environments were mainly controlled by the tectonic settings and climatic conditions, which were determined to control the changes in the water depths, salinity,redox conditions, and lake productivity of the genetic environments. Also, in the symbiotic assemblages, genetic environment changes had induced the development of oil shale deposits, which gradually evolved into coal genetic environments.(4) In the isochronous sequence stratigraphic framework of the coal and oil shale symbiotic assemblages, the lake expansion system tracts (EST) were determined to be the most beneficial to the growth o f all the types of assemblages and were characterized by more assemblage development phases and smaller bed thicknesses. From the early to the late stages of the EST, and from the lakesides to lake centers, the thicknesses of the coal seams in the symbiotic assemblages showed trends of thinning, while the thicknesses of the oil shale deposits exhibited increasing trends. The early stages of high stand system tracts were found to be beneficial to the development of the symbiotic assemblages of coal seams overlying the oil shale. This tract type generally presented large bed thicknesses and distribution ranges. The low stand system tract and the late high stand system tract were determined to be unconducive to the development of the symbiotic assemblages.

Evolution features of in-situ permeability of low-maturity shale with the increasing temperature,Cretaceous Nenjiang Formation,northern Songliao Basin,NE China

Temperature-triaxial pressure permeability testing at the axial pressure of 8 MPa and confining pressure of 10 MPa,closed shale system pyrolysis experiment by electrical heating and scanning electron microscopy analysis are used to study the evolution mechanism of in-situ permeability in the direction parallel to bedding of low-maturity shale from Member 2(K_(2)n_(2))of Cretaceous Nenjiang Formation in northern Songliao Basin with mainly Type I kerogen under the effect of temperature.With the increasing temperature,the in-situ permeability presents a peak-valley-peak tendency.The lowest value of in-situ permeability occurs at 375℃.Under the same temperature,the in-situ permeability decreases with the increase of pore pressure.The in-situ permeability evolution of low-maturity shale can be divided into 5 stages:(1)From 25℃to 300℃,thermal cracking and dehydration of clay minerals improve the permeability.However,the value of permeability is less than 0.01×10^(-3)μm^(2).(2)From 300℃to 350℃,organic matter pyrolysis and hydrocarbon expulsion result in mineral intergranular pores and micron pore-fractures,these pores and fractures form an interconnected pore network at limited scale,improving the permeability.But the liquid hydrocarbon,with high content of viscous asphaltene,is more difficult to move under stress and more likely to retain in pores,causing slow rise of the permeability.(3)From 350℃to 375℃,pores are formed by organic matter pyrolysis,but the adsorption swelling of liquid hydrocarbon and additional expansion thermal stress constrained by surrounding stress compress the pore-fracture space,making liquid hydrocarbon difficult to expel and permeability reduce rapidly.(4)From 375℃to 450℃,the interconnected pore network between different mineral particles after organic matter conversion,enlarged pores and transformation of clay minerals promote the permeability to increase constantly even under stress constraints.(5)From 450℃to 500℃,the stable pore system and crossed fracture system in different bedding directions significantly enhance the permeability.The organic matter pyrolysis,pore-fracture structure and surrounding stress in the different stages are the key factors affecting the evolution of in-situ permeability.

Reaction mechanism and kinetics of pressurized pyrolysis of Chinese oil shale in the presence of water

A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.

In-situ hydrocarbon formation and accumulation mechanisms of micro- and nano-scale pore-fracture in Gulong shale, Songliao Basin, NE China

By conducting experimental analyses, including thermal pyrolysis, micro-/nano-CT, argon-ion polishing field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and two-dimensional nuclear magnetic resonance (2D NMR), the Gulong shale oil in the Songliao Basin was investigated with respect to formation model, pore structure and accumulation mechanism. First, in the Gulong shale, there are a large number of pico-algae, nano-algae and dinoflagellates, which were formed in brackish water environment and constituted the hydrogen-rich oil source materials of shale. Second, most of the oil-generating materials of the Qingshankou Formation shale exist in the form of organo-clay complex. During organic matter thermal evolution, clay minerals had double effects of suppression and catalytic hydrogenation, which expanded shale oil window and increased light hydrocarbon yield. Third, the formation of storage space in the Gulong Shale was related to dissolution and hydrocarbon generation. With the diagenesis, micro-/nano-pores increased, pore diameter decreased and more bedding fractures appeared, which jointly gave rise to the unique reservoir with dual media (i.e. nano-scale pores and micro-scale bedding fractures) in the Gulong shale. Fourth, the micro-/nano-scale oil storage unit in the Gulong shale exhibits independent oil/gas occurrence phase, and shows that all-size pores contain oils, which occur in condensate state in micropores or in oil-gas two phase (or liquid) state in macropores/mesopores. The understanding about Gulong shale oil formation and accumulation mechanism has theoretical and practical significance for advancing continental shale oil exploration in China.

Test method and experimental research on resistance of oil shale under high temperature

Heating the oil shale by current underground to accomplish in-situ transformation process, is a viable direction. The electrical properties of oil shale under different temperatures, especially the resistance, become important. Charging oil shale underground to heat oil shale till kerogen's decomposition temperature, then crude oil and other gases can be generated. The resistance of the oil shale samples was measured by Direct Current (DC) quadripole method to find out the variation rules of resistance value. In the experiments, oil shale presented its semiconductor property. When heated till 350℃-450℃, its resistance changed greatly, optional for heating and cracking. The porosity, oil content, media and composition affected the resistance largely.

Genetic mechanism and petroleum geological significance of calcite veins in organic-rich shales of lacustrine basin:A case study of Cretaceous Qingshankou Formation in Songliao Basin,China

Based on the observation and analysis of cores and thin sections,and combined with cathodoluminescence,laser Raman,fluid inclusions,and in-situ LA-ICP-MS U-Pb dating,the genetic mechanism and petroleum geological significance of calcite veins in shales of the Cretaceous Qingshankou Formation in the Songliao Basin were investigated.Macroscopically,the calcite veins are bedding parallel,and show lenticular,S-shaped,cone-in-cone and pinnate structures.Microscopically,they can be divided into syntaxial blocky or columnar calcite veins and antitaxial fibrous calcite veins.The aqueous fluid inclusions in blocky calcite veins have a homogenization temperature of 132.5–145.1℃,the in-situ U-Pb dating age of blocky calcite veins is(69.9±5.2)Ma,suggesting that the middle maturity period of source rocks and the conventional oil formation period in the Qingshankou Formation are the sedimentary period of Mingshui Formation in Late Cretaceous.The aqueous fluid inclusions in fibrous calcite veins with the homogenization temperature of 141.2–157.4℃,yields the U-Pb age of(44.7±6.9)Ma,indicating that the middle-high maturity period of source rocks and the Gulong shale oil formation period in the Qingshankou Formation are the sedimentary period of Paleocene Yi'an Formaiton.The syntaxial blocky or columnar calcite veins were formed sensitively to the diagenetic evolution and hydrocarbon generation,mainly in three stages(fracture opening,vein-forming fluid filling,and vein growth).Tectonic extrusion activities and fluid overpressure are induction factors for the formation of fractures,and vein-forming fluid flows mainly as diffusion in a short distance.These veins generally follow a competitive growth mode.The antitaxial fibrous calcite veins were formed under the driving of the force of crystallization in a non-competitive growth environment.It is considered that the calcite veins in organic-rich shale of the Qingshankou Formation in the study area has important implications for local tectonic activities,fluid overpressure,hydrocarbon generation and expulsion,and diagenesis-hydrocarbon accumulation dating of the Songliao Basin.

中国石化探区和邻区油页岩原位开采选区评价

中国石化探区油页岩资源丰富,是国家重要的战略储备资源和补充能源。加快油页岩勘探开发对改善中国能源结构和保障国家能源安全具有重要意义。为了实现油页岩规模勘探与效益开发,通过调研梳理国内外成功开展油页岩原位开采现场试验的技术,分析试验区特征、地质和工程适应性、选区选层要求等认为:国外壳牌公司电加热法技术、中国吉林众诚公司的原位压裂化学干馏技术和吉林大学的局部化学反应法原位裂解技术实施了现场先导试验并获得成功,但中国两项技术的成熟度和可行性有待进一步研究论证,且现有的原位开采技术对深部油页岩的适应性均未得到验证。通过开展油页岩原位开采技术特点、地质资源条件、开采工程条件梳理分析,针对约束中国油页岩原位开采的关键因素,结合加热方式确定了4项地质参数、6项工程参数和分级评价界限,并根据约束油页岩原位开采利用的程度确定各参数的权重,建立了油页岩原位开采有利区地质-工程双因素评价模型,优选出15个中国石化探区和邻区油页岩Ⅰ类有利区。对选出的有利区进一步分析其顶底板、断裂、可动水等关键因素的影响,并综合评价优选出4个试验目标区,分别为:鄂尔多斯盆地南缘旬邑区块、博格达山北麓南缘上黄山街含矿区、茂名盆地电白含矿区、抚顺盆地抚顺含矿区。

中低熟页岩油原位转化开采多相多组分演化的数值模拟研究

中低熟页岩油在我国资源量丰富,具有重要的开采价值。目前应用于中低熟页岩油开采的技术中,原位转化技术具有独特的优势,是未来中低熟页岩油开采重要的发展方向。在前人实验室实验和数值模拟计算的基础上,本文利用自主开发的新型多相流数值模拟器,针对布设的井网中具有代表性的区域建立地质模型,通过精细刻画原位转化过程中井周各相各组分的演化过程,进行定性与定量化的分析。模拟结果表明,原位转化中各组分的演化过程受到组分自身黏性、分解反应的临界温度、井间干扰等因素的影响。临界温度的差异与井间干扰会造成加热井周中组分的分层以及富集区的产生,黏性影响对应组分的生产量。本文基于新的数值模拟方法针对中低熟页岩油原位转化中各组分的演化过程进行定性、定量化研究,以期验证原位转化技术的可行性,并为实际的生产提供参考。

页岩油集输过程关键子系统风险评价及安全防控

为提高页岩油集输过程的安全性,首先以过热蒸汽注入油页岩原位转化技术下的页岩油集输过程为评价对象,分析页岩油集输过程中的危险源,将整个集输过程分为3个子系统,利用危险性与可操作性分析(HAZOP)法定性分析各子系统的风险,并根据定性分析结果,利用保护层分析法(LOPA)和火灾爆炸指数法(F&EI)计算各子系统发生火灾爆炸事故的概率与危险等级;然后划分页岩油集输过程的节点,对含有硫化氢的油气泄漏事故与净化后的油气泄漏事故分别建立蝴蝶结模型,并依据风险评价结果,制定有效的安全防控措施和风险管理体系。结果表明:油气集输过程可能引发事故的子系统有蒸汽发生系统、冷却分离系统、氨法脱硫系统与冷却分离系统,其中,蒸汽发生系统泄漏不会造成火灾爆炸事故,其余子系统的火灾爆炸风险程度由重到轻依次为:氨法脱硫系统、冷却分离系统、提气脱硫系统。

预热气体对油页岩自生热原位转化效果的影响

地下原位转化是油页岩工业化开发的必然趋势,自生热法是实现油页岩地下原位转化的一种复合高效加热方法。为探究预热阶段不同高温载气对油页岩自生热原位转化效果的影响,以我国吉林扶余地区油页岩为例,分别在预热阶段注入氮气、空气、蒸汽、二氧化碳4种高温气体进行数值模拟分析,对比最终油气产量和能量回收率的差异。以预热阶段注高温氮气组作为对照组,结果表明注高温空气、蒸汽和二氧化碳完成开采所需时间分别降低22%、39%、12%,最大能量回收率分别提高55%、86%、23%,总油收量分别降低5%、提高18%和降低11%。从开采完成时间、能量回收率及总油收量角度来看,注蒸汽预热效果最佳。因此,综合对比可得,注蒸汽预热的自生热开采方法可有效增大油收量、降低开采所需时间、提高能量利用率。

中国油页岩原位开采可行性初探

中国油页岩资源量为11 602×108t,其中埋藏深度在500～1 500 m的油页岩资源量为6 813×108t,原位开采技术是开发该部分资源的有效手段。中国油页岩原位开采技术处于实验阶段,通过对油页岩热分解、热破裂规律、渗透变化规律等方面的研究,初步探索了油页岩原位开采的可行性。油页岩热分解过程可以分为3个阶段:干燥脱水、热解生油、无机矿物质的分解。在这3个阶段中,由于油页岩内部物理化学反应的程度不同,导致孔隙和裂缝发生了不同程度的变化,变化最大的是热解生油阶段。利用非稳态数学模型研究了油页岩电加热原位开采的温度场分布,表明加热5 a后可以对页岩油进行开采,产油时间至少可以维持2 a。

基于原位转化/改质技术的陆相页岩选区评价——以鄂尔多斯盆地三叠系延长组7段页岩为例

与依靠水平井体积压裂技术的页岩气、致密油开发相比,原位转化/改质技术更适合规模效益开发中国陆相大面积分布、成熟度介于0.5%~1.0%、总有机碳质量分数大于6%的页岩层系液态烃资源.本研究基于原位转化/改质技术具有不受地质条件限制、地下转化轻质油、高采出程度、较低污染等技术优势的特点,综合考虑鄂尔多斯盆地延长组7段页岩厚度、页岩有机质丰度、热演化程度和现今埋深等地质参数,评价优选试验有利区主要分布在盆地东南部,其中埋深小于1 500 m的分布面积大于6 000 km^2.页岩选区评价结果表明,鄂尔多斯盆地陆相页岩是原位转化/改质技术工业试验的有利页岩分布区.