中国陆相页岩油类型、资源潜力及与致密油的边界

陆相页岩油包括中低成熟度和中高成熟度两大资源类型,二者在资源赋存环境、潜力、开采方式与使用技术以及工业评价标准等方面均不同,此外,陆相页岩油与美国页岩油和致密油也有诸多不同,科学界定这些资源类型的不同内涵,对推动陆相页岩油勘探从"源外"进入"源内",成为未来战略接替资源具有重要意义。明确了中低成熟度和中高成熟度两类陆相页岩油的内涵,前者是指埋藏300 m以深且Ro值小于1.0%的陆相富有机质页岩层系中赋存的液态烃和多类有机物的统称,后者是指埋深在蒂索(Tissot)模式"液态窗"范围、Ro值大于1.0%的富有机质页岩段中存在的液态石油烃的总称;系统总结了不同类型陆相页岩油的地质特征、资源潜力和经济评价标准。经评价,中国中低成熟度页岩油原位转化技术可采资源量约为(700~900)×10^8 t,中等油价(60~65美元/bbl)下的经济可采量为(150~200)×10^8 t,是保证陆相页岩油革命发生的主体,应依据井组累计采出量规模、建产规模、保存条件及开采经济性等关键参数,优选试验靶区,同时攻关核心技术装备;中高成熟度页岩油地质资源量约100×10^8 t,可采量尚需在单井日产量与累计采出量达至经济门限后确定。陆相页岩油与致密油有明确的边界,存在岩性组合、相带分布与产能评价标准等不同,二者可以按不同资源类型独立区分、并行存立。中国陆相页岩油类型、资源潜力及与致密油边界系统厘定,可为即将到来的页岩油勘探开发实践提供借鉴,有助于中国陆相页岩油革命的顺利发展。

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。

非常规油气地质学建立及实践

非常规油气地质学理论是世界石油工业从常规油气向非常规油气跨越的一次理论飞跃。紧密结合中国特殊地质背景和油气工业条件,经过10年不懈攻关,通过构建细粒沉积学、非常规油气储层地质学、非常规油气成藏地质学、非常规油气开发地质学、常规—非常规油气"共生盆地"发展战略等学科内容,基本形成非常规油气地质学理论体系框架。非常规油气地质学理论,是世界页岩油和气、致密油和气等典型非常规油气工业发展的理论基础,引领推动了石油地质学科发展、行业标准制定、国家实验室建设和专业人才培养,有效推进了我国致密油和气、页岩油和气等非常规油气资源的工业勘探开发。非常规油气地质学科在未来油气资源综合利用、能源结构科学预判、复杂问题创新解决等方面,仍有发展空间。

吉木萨尔凹陷芦草沟组致密油、页岩油地质特征与勘探潜力

准噶尔盆地二叠系芦草沟组是中国最为古老的陆相液态烃页岩层系之一,是近海咸化湖盆混积岩沉积,具有丰富的致密油、页岩油资源,吉木萨尔凹陷是准噶尔盆地东部典型富液态烃凹陷。基于页岩层系实际地质资料分析,发现吉木萨尔凹陷芦草沟组页岩层系发育上、下两个含油系统,具有源储一体、薄层叠置、厚度较大、整体含油、连续分布的特征:(1)近海湖泊沉积环境,间歇性海水注入使湖泊生物群体死亡,利于有机质富集保存;细粒混积岩沉积为主,划分为6层2.5个三级沉积旋回;(2)烃源岩主要发育在芦草沟组第2段(P2l2)和第5段(P2l5),岩性主要为碳酸盐质泥岩和硅质泥岩,有机碳含量多大于4%,Ⅱ型干酪根为主,Ro介于0.6%~1.1%,处于生油窗口;(3)储层普遍较致密,岩性主要为碳酸盐岩、碳酸盐质砂岩、硅质砂岩,孔隙度主体介于6%~12%,空气渗透率小于0.1 m D,连通孔喉直径主体介于几十至几百纳米,以粒内孔、粒间溶蚀孔为主,含油饱和度多介于80%~90%,储油条件较好;(4)地层流体压力系统以常压—弱超压为主,原油密度平均为0.8971g/cm^3,50℃平均黏度为165.2m Pa·s,为低—中等热演化程度产物,地层条件下整体流动性较差。吉木萨尔凹陷芦草沟组致密油、页岩油资源丰富,经评价致密油技术可采资源量为0.91×10~8t,其中P_2l_1和P_2l_4是致密油"甜点段",致密油"甜点区"主要分布于凹陷中部;页岩油技术可采资源量为1.10×10~8t,其中P_2l_2和P_2l_5是页岩油"甜点段",页岩油"甜点区"也主要分布于凹陷中部。

陆相富有机质页岩与泥岩的成藏差异及其在页岩油评价中的意义

页岩和泥岩的有机质丰度与岩石组构差异较大,决定了二者对常规油气与页岩油气成藏贡献的不同,未来进入源灶区勘探后所倚重的烃源岩评价标准也应有别。页岩沉积于半深湖-深湖环境,沉积速率低并伴有程度不等的化学沉积作用;泥岩多形成于滨-浅湖环境,沉积速率快且多具密度流特征。火山灰沉落与热液注入导致“肥沃效应”、放射性物质促使生物超量超速生长、深水厌氧环境与低沉积速率保护有机物堆积不被稀释等因素促使页岩段有机物富集。页理易剥离成为储集空间,生烃产生的酸性水溶蚀部分颗粒形成增孔效应;泥岩呈块状,黏土矿物含量高,基质孔隙不发育。页岩段总有机碳含量高,页理发育,储集性相对较好,脆性矿物含量相对较高,是页岩油勘探开发最有利的岩相类型。开展页岩与泥岩成藏差异研究,以页岩、泥岩为端元,落实资源分布,确定“甜点”评价参数类型和标准,优选页理发育的“甜点区/段”,使用有效开发技术,对客观评价页岩油资源总量、经济性与规模有效开发都具重要意义。

中国石油油气资源潜力分析与勘探选区思考

随着油气勘探工作的不断深入,勘探难度日益加大、勘探对象和资源赋存条件更加复杂,更加亟需明确油气勘探现状与挑战,评价国内常规与非常规油气资源潜力,明确剩余油气资源分布特点,评价落实重点勘探领域与有利勘探区带,夯实油气资源家底。中国石油天然气集团有限公司面对新形势、新要求,提出五大举措强力推进油气勘探,取得了10项战略发现和10项重大突破,中西部地区集中勘探落实了15个规模储量区,油气探明储量持续保持高位增长。梳理了中国石油近十年来油气油气勘探形势、挑战及重要举措,分析了中国石油剩余油气资源潜力及分布状况,论述了中国石油探区未来油气勘探重点领域、方向和区带,明确提出深层海相碳酸盐岩、岩性地层、前陆冲断带下组合以及页岩油等四大领域是未来油气勘探突破发现和规模增储的重点。

页岩油气最终采收量地质主控因素——以美国海湾盆地鹰滩页岩为例

基于白垩系鹰滩组下段1317口生产井和72口系统取心井991组分析化验数据,分别按油和天然气,采用两种页岩油气最终采收量(EUR)经典模型预测单井最终采收量,以消除工程因素的预测均值作为最终结果,全面厘清控制页岩油气EUR的关键地质因素。研究表明:储集能力、资源量、流动能力和可压性是控制页岩油气EUR的4个关键地质因素。储集能力直接受控于总孔隙度和含烃孔隙度,间接受控于TOC和R_(o);资源量受控于含烃孔隙度、有效页岩厚度等参数;流动能力受控于有效渗透率、原油密度、气油比、凝析油气比、地层压力梯度和R_(o)等参数;可压性直接受控于脆性指数,间接受控于黏土体积含量。页岩油气EUR主要受控于6个地质参数,EUR与有效页岩厚度、总有机碳含量、裂缝孔隙度呈正相关关系,与黏土体积含量呈负相关关系,与R_(o)、地层压力梯度呈先增大后减小关系。现有水平井压裂技术的单井有效压裂厚度上限约65 m;EUR下限值为3×10^(4)m^(3)油当量条件下,当TOC<2.3%或R_(o)<0.85%或黏土体积含量大于25%,且裂缝或微裂缝不发育时,很难形成页岩油气的有利发育区。

鄂尔多斯盆地延长组长_7页岩层段岩石热导率特征及启示

原位转化技术是中国陆相页岩油攻关的重点领域,鄂尔多斯盆地三叠系延长组长_7页岩层段岩石热物性,特别是高温热物性研究尚处空白,严重制约原位转化工程优化和可行性评价。选取长_7页岩发育区内多口取心井新鲜样品,利用热导仪、差示扫描量热仪和热膨胀仪,获得长_7页岩层段泥质粉砂岩、凝灰岩、泥岩和页岩的热扩散系数、比热容、热膨胀系数以及热导率参数。长_7页岩层段不同岩性的岩石热扩散系数和热导率存在差异,且随砂质含量降低而降低,即泥质粉砂岩>凝灰岩>泥岩>页岩。热扩散系数和热导率具有各向异性,水平方向是垂直方向的1～3.5倍,且其差异随温度升高而增大。随温度升高,岩石热扩散系数呈降低趋势、比热容呈增大趋势、热导率呈先降低后增大趋势。页岩热物性的各向异性最强,各向异性是岩石非均质性的体现,与微观纹层相关;砂岩各向异性可能与岩石不同方向上渗透率相关。

塔北隆起-库车坳陷西段差异构造变形特征及其控制因素

塔北隆起-库车坳陷是塔里木盆地重要的油气富集区,探讨区域构造特征及主要控制因素对油气勘探具有重要意义。利用地球物理资料,应用生长地层及应力学分析方法对研究区地震剖面进行解释与复原,并对区域内主要新生界生长构造发育的时序进行界定。研究结果表明,区内东西段构造挤压时间及变形特征存在明显差异。新生界挤压构造发育时间自东向西由早到晚,沿古近系滑脱面,新生界构造变形自北部向盆内传播的距离差别显著:西段传播距离较远,东段较近;西部滑脱构造发育,冲断构造较少,中、东部相反,新生界构造变形局限于库车坳陷内。通过综合对比分析,造山带挤压背景下区域内古应力场在古近纪后发生明显的逆时针压扭,古近系膏泥岩层为构造变形向盆内传播提供了重要条件,大型冲断构造的发育及坳隆转换带基底的挠曲有效地释放分解了来自北部的挤压作用,这是区内构造特征东西差异的主要原因。

基于互联网技术石油地质实验室客户服务平台设计与实现

随着业务量的不断增加,在工作人员数量不变的基础上,传统服务模式难以承担更多检测业务来保障检测工作及时有序进行。为了让客户享受到更优质的服务,结合油气实验领域客户服务的工作现状,运用互联网技术研发了能满足油气实验领域特性的客户服务平台。平台提供仪器设备预约、在线远程申请实验、实验过程跟踪、实验报告下载、满意度调查等服务;同时支持移动端和电脑端,与微信公众号进行深度集成,便于用户业务受理,多线程并行,大大缩短了业务流转的时间。实践表明,客户服务系统对提高实验室综合管理质量、提高运营效率,发挥了积极的作用。

页岩原位改质技术现状、挑战和机遇

全球页岩层系蕴含丰富的致密油气、页岩油气等非常规油气资源,但对于资源量巨大的页岩油中美两国均没实现真正突破。中国石油勘探开发研究院与荷兰皇家壳牌页岩油联合小组认为原地开采改质适用于中国,通过大量国内外文献调研,明确原位开采技术的现状与工业意义。归纳出工业化面临缺少精确测定地质工程参数的技术和大型原位转化数值模拟平台、缺少对全过程工艺的精细优化及经济评价—工程设计间的动态互馈、缺少评估页岩原位转化对大气环境和水资源方面的影响评价三大挑战。梳理出页岩原位改质三大攻关重点,即研究纳米导热流体等导热技术、研发适用于地下条件的生烃催化剂、研制耐高压耐高温抗酸碱腐蚀的加热材料。倡导运用地质工程一体化的运作模式和融合多学科多参数的大型数值模拟平台,开展原位改质有利区优选、勘探开发潜力与经济性评价。最后,结合中国页岩的地质特征,对中国页岩油原位改质技术的应用提出页岩层系非常规油气资源立体勘探、一体化开发等建议,助推中国页岩原位改质示范区的建立。

中国陆相页岩油类型、潜力及前景

近年来,中国石油对外依存度逐年攀升,国家能源安全形势日趋严峻,与此同时,北美“页岩革命”则如火如荼地进行。在此背景下,为拓宽中国油气勘探开发领域,寻找原油增储上产接替资源,对中国陆相页岩油的资源类型、潜力及发展前景进行了系统研究。分析认为,中国陆相页岩油具有四方面地质特征,并可按成熟度划分为中高成熟度和中低成熟度两大类型。两类陆相页岩油资源潜力均较大,中高成熟度页岩油地质资源量约为200×108t,中低成熟度页岩的原位转化远景技术可采石油资源量大。近年来,陆相页岩油勘探获得诸多进展,中高成熟页岩油方面,源储一体型、源储分异型、纯页岩型3种类型均有勘探发现;中低成熟度页岩油方面,正处于原位转化技术探索试验阶段。针对陆相页岩油未来发展,系统梳理了四大风险点,并结合中国国情及地质实际提出相应对策。综合研究认为,中国陆相页岩油有望实现工业化开发,并成为中国原油增储上产的重大接替领域。

鄂尔多斯盆地三叠系长7富有机质段岩石热膨胀系数随温度演化特征及启示

页岩油地下原位转化技术的应用是实现中低成熟度页岩油规模开发利用的有效手段,加热过程中页岩的热膨胀研究对于井眼稳定性、加热器寿命以及盖层完整性等工程评价具有重要意义。选取鄂尔多斯盆地三叠系长7页岩段3口取心井的岩心,在常规镜下薄片观察、X射线衍射分析基础上,采用DIL402 SE型热膨胀仪获得25~600℃下泥质粉砂岩、泥岩和黑色页岩的热膨胀系数及其动态演化特征。研究结果表明:(1)鄂尔多斯盆地三叠系长7富有机质段不同岩性的热膨胀系数存在较大差异,并随有机碳含量(TOC)的升高而增大。当TOC值小于5%时,岩石热膨胀系数“近指数型”增大;当TOC值大于等于5%时,岩石热膨胀系数呈“四段式”复杂变化。(2)研究区富有机质页岩的热膨胀系数各向异性因子最大,垂直层理方向上是平行层理方向上的1.7~2.7倍。(3)富有机质页岩生烃强度大,能产生微裂缝并导致热膨胀复杂变化。

Progress in China's Unconventional Oil & Gas Exploration and Development and Theoretical Technologies

The new century has witnessed a strategic breakthrough in unconventional oil ＆ gas.Hydrocarbon accumulated in micro-/nano-scale pore throat shale systems has become an important domain that could replace current oil ＆ gas resources.Unconventional oil ＆ gas plays an increasingly important role in our energy demand.Tight gas,CBM,heavy oil and asphaltic sand have served as a key domain of exploration ＆ development,with tight oil becoming a ＇bright spot＇ domain and shale gas becoming a ＇hotspot＇ domain.China has made great breakthroughs in unconventional oil ＆ gas resources,such as tight gas,shale gas,tight oil and CBM,and great progress in oil shale,gas hydrate,heavy oil and oil sand.China has an estimated（223-263）×10~8t of unconventional oil resources and（890-1260）×l0^（12）m^3 of gas resources.China has made a breakthrough for progress in unconventional oil ＆ gas study.New progress achieved in fine-grained sedimentary studies related to continental open lacustrine basin large-scale shallow-water delta sand bodies,lacustrine basin central sandy clastic flow sediments and marine-continental fine-grained sediments provide a theoretical basis for the formation and distribution of basin central reservoir bodies.Great breakthroughs have been made in unconventional reservoir geology in respect of research methodology ＆ technology,multi-scale data merging and physical simulation of formation conditions.Overall characterization of unconventional reservoirs via multi-method and multi-scale becomes increasingly popular and facilitates the rapid development of unconventional oil ＆ gas geological theory,method and technology.The formation of innovative,continuous hydrocarbon accumulation theory,the establishment of the framework of the unconventional oil ＆ gas geological theory system,and the determination of the implications,geological feature,formation mechanism,distribution rule and core technology of unconventional oil＆ gas geological study lays a theoretical foundation for extensive unconventional oil ＆ gas exploration and development.Theories and technologies of unconventional oil ＆ gas exploration and development developed rapidly,including some key evaluation techniques such as ＇sweet spot zone＇ integrated evaluation and a six-property evaluation technique that uses hydrocarbon source,lithology,physical property,brittleness,hydrocarbon potential and stress anisotropy,and some key development ＆engineering technologies including micro-seismic monitoring,horizontal drilling ＆ completion and ＂factory-like＂ operation pattern, ＂man-made reservoir＂ development,which have facilitated the innovative development of unconventional oil ＆ gas.These breakthroughs define a new understanding in four aspects：①theoretical innovation;② key technologies;③ complete market mechanism and national policy support;and ④ well-developed ground infrastructure,which are significant for prolonging the life cycle of petroleum industry,accelerating the upgrade and development of theories and technologies and altering the global traditional energy structure.

Types and resource potential of continental shale oil in China and its boundary with tight oil

Continental shale oil has two types, low-medium maturity and medium-high maturity, and they are different in terms of resource environment, potential, production methods and technologies, and industrial evaluation criteria. In addition, continental shale oil is different from the shale oil and tight oil in the United States. Scientific definition of connotations of these resource types is of great significance for promoting the exploration of continental shale oil from "outside source" into "inside source" and making it a strategic replacement resource in the future. The connotations of low-medium maturity and medium-high maturity continental shale oils are made clear in this study. The former refers to the liquid hydrocarbons and multiple organic matter buried in the continental organic-rich shale strata with a burial depth deeper than 300 m and a Ro value less than 1.0%. The latter refers to the liquid hydrocarbons present in organic-rich shale intervals with a burial depth that in the "liquid window" range of the Tissot model and a Ro value greater than 1.0%. The geological characteristics, resource potential and economic evaluation criteria of different types of continental shale oil are systematically summarized. According to evaluation, the recoverable resources of in-situ conversion technology for shale oil with low-medium maturity in China is about(700-900)×10^8 t, and the economic recoverable resources under medium oil price condition($ 60-65/bbl) is(150-200)×10^8 t. Shale oil with low-medium maturity guarantees the occurrence of the continental shale oil revolution. Pilot target areas should be optimized and core technical equipment should be developed according to the key parameters such as the cumulative production scale of well groups, the production scale, the preservation conditions, and the economics of exploitation. The geological resources of medium-high maturity shale oil are about 100×10^8 t, and the recoverable resources can to be determined after the daily production and cumulative production of a single well reach the economic threshold. Continental shale oil and tight oil are different in lithological combinations, facies distribution, and productivity evaluation criteria. The two can be independently distinguished and coexist according to different resource types. The determination of China’s continental shale oil types, resources potentials, and tight oil boundary systems can provide a reference for the upcoming shale oil exploration and development practices and help the development of China’s continental shale oil.

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.

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.

Accumulation contribution differences between lacustrine organic-rich shales and mudstones and their significance in shale oil evaluation

The differences in organic matter abundance and rock composition between shale and mudstone determine the discrepancy of their contributions to the formation of conventional and shale oil/gas reservoirs.The evaluation criteria of source rocks are different in the future exploration in self-sourced petroleum systems.Shales are deposited in deep/semi-deep lacustrine,with low sedimentation rate and chemical depositions of various degrees,while mudstones are mostly formed in shallow lacustrine/lakeside,with high deposition rate and density flow characteristics.Three factors contribute to the enrichment of organic matter in shales,including the"fertility effect"caused by volcanic ash deposition and hydrothermal injection,excessive and over-speed growth of organisms promoted by radioactive materials,and deep-water anaerobic environment and low sedimentation rate to protect the accumulation of organic matter from dilution.Lamellations in shales are easy to be stripped into storage space,and acid water produced during hydrocarbon generation can dissolve some particles to generate new pores.The massive mudstones with high clay content are of poor matrix porosity.Shales with high total organic carbon,developed laminations,relatively good reservoir property,and high brittle mineral content,are the most favorable lithofacies for shale oil exploration and development.It is necessary to conduct investigation on the differences between shale and mudstone reservoirs,to identify resources distribution in shale and mudstone formations,determine the type and standard of"sweet-spot"evaluation parameters,optimize"sweet-spot areas/sections",and adopt effective development technologies,which is of great significance to objectively evaluate the total amount and economy of shale oil resources,as well as the scale of effective exploitation.

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.

压力对页岩原位加热产出油气特征的影响——以鄂尔多斯盆地三叠系延长组7段3亚段页岩为例

鄂尔多斯盆地三叠系延长组7段(长7段)页岩成熟度低、有机碳含量高、有机质类型较好,原位加热开发页岩油气的潜力巨大。为了探讨原位加热过程中压力对页岩产出油气特征的影响,为原位加热开发长7段页岩油气方案提供可靠依据,以长7段3亚段页岩为研究对象,对其典型样品以20℃/d的升温速率进行了4组不同压力(0 MPa、2 MPa、4 MPa、8 MPa)的原位加热模拟实验。实验结果表明:在相同加热条件下,压力变化对长7段页岩的最大产油量和产出油性质均有影响,对产出气体组成的影响更大。在4组不同压力下,长7段页岩原位加热的最大产油量为36.97~41.47 kg/t,产油量随压力增加有一定减少。随着压力增加,产出油中轻质组分增加,油品变好,其原因在于高压下有机质生成的重质油的裂解程度相对较高;当加热到450℃时,总产气量为14.28~21.05 m^(3)/t,总产气量随压力增加而增加。4组实验序列产出页岩油气的气油比(289.70~427.04 m^(3)/m^(3))随着压力增加而增大;不同气体组分随着压力增加产量变化差异较大,其中,烃类气体与CO_(2)的总产气量随压力增加而增大,H_(2)产量随压力增加而明显减少,H_(2)S产量随压力增加变化较小。不同气体组分的产量随压力增加呈现出不同的变化规律,这与加热温压范围内不同气体的形成机理、页岩对不同气体组分吸附能力的差异和一些次级反应等因素有关。根据不同压力下页岩原位加热的产油量、油品、不同气体组分的产率,结合考虑油气价格与油气处理成本,提出在实施原位加热开发长7段页岩油气时应尽量保持低的生产井井底流压的建议,这一认识对长7段原位加热页岩油气开发方案的确定具有重要的参考意义。