Genesis of the low-permeability reservoir bed of upper Triassic Xujiahe Formation in Xinchang gas field,western Sichuan Depression

The genesis of a reservoir is a result of the combined action of deposition, diagenesis, tectonic reworking, and interaction of rock and fluid and the evolutionary environment. We discuss the genetic and evolution mechanism of a low-permeability reservoir bed of the Xujiahe Formation in the western Sichuan Depression on the basis of the study of diagenesis, diagenetic reservoir facies and the diagenetic evolution sequence. The research indicated that this reservoir bed can be divided into five types of diagenetic reservoir facies, namely strong dissolution, chlorite-lined intergranular pores, compaction and pressure solution, carbonate cementation and secondary quartz increase. There are, however, just two diagenetic reservoir facies which provide low-permeability reservoir beds, namely strong dissolution and chlorite-lined intergranular pores. We also analyzed their diagenetic evolution sequences and the origin of the low-permeability reservoir bed. Besides, it was also indicated that the composition and structure of sandstones, types of sedimentary microfacies, diagenesis history as well as the tectonic reworking in later periods are the main factors controlling the formation of the low-permeability reservoir bed. The above- mentioned factors establish the foundation for the forecasting the distribution of high quality reservoir beds.

Micro pore and throat characteristics and origin of tight sandstone reservoirs: A case study of the Triassic Chang 6 and Chang 8 members in Longdong area, Ordos Basin, NW China

The microstructure differences of the Triassic Chang 6 and Chang 8 members tight reservoirs in the Longdong area of Ordos Basin were compared by means of cast thin sections, scanning electron microscope, X-ray diffraction, and constant rate mercury injection. Their pore evolution models were established, and the effects of main diagenesis on densification were examined. The throat is the main factor controlling the physical properties of the Chang 6 and Chang 8 members reservoirs: The lower the permeability, the smaller and the more concentrated the throat radius and the larger the proportion of the throats in the effective storage space. There are several obvious differences between Chang 6 and Chang 8 members:(1) with the increase of permeability, the contribution of the relative large throats to the permeability in the Chang 8 member reservoir is more than that in the Chang 6 member reservoir;(2) the control effect on pore-throat ratio of the nano-throats in the Chang 6 member reservoir is more significant. The sedimentary action determines the primary pore structure of the Chang 6 and Chang 8 members sand bodies, and the diagenesis is the main factor controlling the densification of the reservoirs. Because of the difference in rock fabrics and the chlorite content of Chang 6 and Chang 8, the strong compaction resulted in less porosity reduction(17%) of the Chang 81 reservoir with larger buried depth and larger ground temperature than the Chang 63 reservoir(19%). The siliceous, calcareous and clay minerals cement filling the pores and blocking the pore throat, which is the key factor causing the big differences between the reservoir permeability of Chang 6 and Chang 8 members.

Comparison of basic features and origins of oolitic shoal reservoirs between carbonate platform interior and platform margin locations in the Lower Triassic Feixianguan Formation of the Sichuan Basin,southwest China

The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases worldwide,can be divided into two locations in general,i.e.,platform interior and platform margin locations.Their differences of reservoir features and origins,however,have not been investigated comprehensively due to different exploration degrees.This issue is addressed in this paper,to provide basic data and information for the basin＇s hydrocarbon exploration and for the study of carbonate platform sedimentology and reservoir geology worldwide.We compared the features of these two types of reservoirs in detail,including the depositional and diagenetic features,pore types and petrophysical features.Based on the comparison,the origin of the reservoirs was further discussed.It is shown that the reservoirs in platform interior and platform margin locations differ significantly.The interior carbonates were deposited in moderate to high energy settings and the dominant lithologic type was limestone,which was weakly compacted and intensely cemented and has undergone meteoric dissolution.Pore types include intragranular dissolution and moldic pores,with low porosities（6%） and low permeabilities（0.1 mD）.By contrast,the platform margin carbonates were deposited in relatively high energy settings and mainly consisted of dolostones with some limestones.The rocks were strongly compacted but incompletely cemented.As a result,some primary intergranular pores were preserved.Both meteoric solution and burial solution have taken place.There are various types of pore spaces including intergranular and intercrystalline solution pores and residual intergranular pores.This type of reservoir generally has better petrophysical properties（9% porosity and 0.1 mD permeability） and pore-throat structures than the interior reservoirs.These differences were influenced by both primary depositional features and secondary diagenesis.For the interior carbonate reservoirs,early meteoric dissolution,weak compaction and strong cementation are important controlling factors.By contrast,the factors controlling the formation of the margin carbonate reservoirs mainly include dolomitization,preservation of primary pores and burial dissolution.

A quantitative evaluation for well pattern adaptability in ultra-low permeability oil reservoirs:A case study of Triassic Chang 6 and Chang 8 reservoirs in Ordos Basin

Based on the previous studies and development practice in recent 10 years, a quantitative evaluation method for the adaptability of well patterns to ultra-low permeability reservoirs was established using cluster analysis and gray correlation method, and it includes 10 evaluation parameters in the four aspects of optimal evaluation parameters, determination of weights for evaluation parameters, development stage division, and determination of classification coefficients. This evaluation method was used to evaluate the well pattern adaptability of 13 main ultra-low permeability reservoirs in Triassic Chang 6 and Chang 8 of Ordos Basin. Three basic understandings were obtained: Firstly, the well pattern for ultra-low permeability type-I reservoirs has generally good adaptability, with proper well pattern forms and well pattern parameters. Secondly, square inverted nine-spot well pattern is suitable for reservoirs with no fractures; rhombic inverted nine-spot injection pattern is suitable for reservoirs with some fractures; and rectangular well pattern is suitable for reservoirs with rich fractures. Thirdly, for the ultra-low permeability type-Ⅱ and type-Ⅲ reservoirs, with the principles of well pattern form determination, the row spacing needs to be optimized further to improve the level of development of such reservoirs.

Binary pore structure characteristics of tight sandstone reservoirs

The pore structure and its influence on physical properties and oil saturation of the Triassic Chang 7 sandstones,Ordos Basin were discussed using thin sections,physical properties,oil saturation and mercury intrusion data.The results show that the tight sandstone has a binary pore structure:when the pore throat radius is larger than the peak radius,the pore radius is significantly larger than throat size,the pore structure is similar to the bead-string model with no fractal feature,and the pore throat volume is determined by the pore volume.When the pore throat radius is smaller than the peak radius,the pore structure is close to the capillary model and shows fractal features,the pore size is close to the throat size,and the pore throat volume is determined by the throat radius.The development of pore throats larger than the peak radius provides most of the oil storage space and is the major controlling factor for the porosity and permeability variation of tight sandstone.The pore throat smaller than the peak radius(including throats with no mercury invaded)contributes major reservoir space,it shows limited variation and has little effect on the change of physical properties which is lack of correlation with oil saturation.The pore throat larger than the peak radius is mainly composed of secondary and intergranular pores.Therefore genesis and main controlling factors of large pores such as intergranular and dissolved pores should be emphasized when predicting the tight sandstones quality.

准噶尔盆地玛湖凹陷三叠系百口泉组储层特征及油气成藏规律

通过岩心分析测试、地震厚度预测、包裹体成藏期次分析以及源储配置关系研究,对准噶尔盆地玛湖凹陷三叠系百口泉组储层特征及油气成藏规律进行了刻画。研究结果表明:①玛湖凹陷斜坡区三叠系百口泉组主要发育扇三角洲沉积,岩性普遍较粗,相对优质的储集层主要分布于扇三角洲前缘水下分流河道微相及少量河口砂坝微相中,其成分以长石岩屑砂砾岩为主,其次为岩屑砂砾岩。岩石普遍较致密。岩心孔隙度为3.17%~23.40%,平均为9.04%,渗透率为0.01~934.00mD,平均为0.73mD,属低孔特低渗型储集层。储集空间类型以次生溶孔为主,可见粒间缝和其他微裂缝。②研究区油气主要来源于下二叠统风城组碱湖沉积的泥页岩,最厚处超过400m,为残留海—潟湖相沉积,水体盐度较高,岩性以云质泥岩和泥质岩为主。有机质类型以Ⅰ和Ⅱ1型为主,总有机碳含量(TOC)多大于1.0%,生烃潜量(S1+S2)多大于6.0mg/g,氯仿沥青“A”平均为0.2%,HI平均为322mg/g,有机质演化处于成熟阶段,为中等—好烃源岩。③研究区具有3期成藏特征,晚三叠世之前为第1期油气充注,未能聚集成藏,早侏罗世为第2期油气充注期,对应黄色荧光烃类包裹体;早—中白垩世为第3期油气充注期,对应蓝白色荧光烃类包裹体,后2期油气充注对百口泉组油气成藏起主要贡献作用。④研究区源储配置紧密性是导致玛湖西斜坡和玛湖东斜坡油气差异性聚集的核心要素。

致密砂岩孔隙演化及其对含油饱和度的影响——以鄂尔多斯盆地甘泉地区三叠系延长组长6—长8段储层为例

致密砂岩储层的微观非均质性强,含油饱和度变化大。为了探究致密砂岩储层成岩过程中孔喉大小分布的变化及其对含油饱和度的影响,以鄂尔多斯盆地甘泉地区三叠系延长组长6—长8段致密砂岩储层为例,利用铸体薄片、扫描电镜、高压压汞等测试手段,定量计算了成岩作用对孔隙度的影响。在此基础上,以孔喉参数的统计模型为约束条件,建立了主要成藏期孔喉大小分布模型,利用积分方法计算出了主要成藏期的可动流体饱和度。甘泉地区长6—长8段致密砂岩储层在早成岩期—中成岩期受到强烈的压实作用,平均压实减孔率为81.85%,胶结作用进一步使孔隙度平均降低11.00%左右,溶蚀作用虽然增加了孔隙空间,但增幅较小,平均为4.38%;主要成藏期开始(128 Ma)和结束(111 Ma)对应的平均古孔隙度分别为13.82%和8.68%,大于最小流动孔喉半径(0.1μm)的孔喉体积占比低,可动流体饱和度为35.05%~93.27%。主要成藏期孔喉半径及可动流体饱和度偏低是含油饱和度低的原因之一。受储层自生黏土矿物对岩石润湿性的影响,现今含油饱和度值并未急剧降低。成藏时期孔喉大小分布模型计算油层可动流体饱和度为研究类似地区油气储层孔喉大小演化及其与含油饱和度的关系提供了一种可行的分析方法。

孔隙型致密砂岩气藏产能控制因素

为了探究天然裂缝欠发育致密砂岩气藏的产能主控因素,以四川盆地北部元坝地区上三叠统须家河组二段和川中东峰场地区须家河组五段气藏为研究对象,分析了二者的地质特征、钻井工艺和储层改造技术,明确了孔隙型致密砂岩气藏天然气产能主控因素。研究结果表明:①古、今构造高部位是油气运聚成藏的指向区,天然气富集程度较高,气井高产概率较大,而构造低部位气井生产效果较差;②储层物性越好,成藏过程中天然气富集程度越高,且生产过程中天然气流动能力较强,故优质储层发育段越厚,气井产量越高;③裂缝欠发育致密砂岩气藏需通过储层改造才能获产,加大改造规模对优质储层发育的钻井增产效果明显;④由于致密砂岩储层局部发育,水平井能够钻遇更多的优质储层,故较直井而言,提产效果明显;⑤由于钻井液中的重晶石会对物性差—中等的储层造成污染,进而影响产量,故致密砂岩气藏钻井过程中需加强储层保护。结论认为:①孔隙型致密砂岩气藏产能主要受古、今构造位置,优质储层发育程度,储层改造规模和井型等因素控制;②优质烃源岩发育区、正向构造区和相对优质储层发育区的叠合部位可优先考虑部署井位。

鄂尔多斯盆地三叠系延长组长7段页岩气储层特征及其勘探开发前景

鄂尔多斯盆地作为我国的第二大沉积盆地,油气勘探潜力巨大。盆地内三叠系延长组7段富有机质烃源岩发育广泛,分布范围达(4~5)×10^(4) km^(2)。该套烃源岩有机质丰度高,有机质类型为Ⅰ—Ⅱ_(1)型,R_(o)主要分布在0.9%~1.2%之间,处于热演化成熟阶段,滞留烃含量大,为大规模页岩油气藏的发育奠定了重要物质基础。长7_(3)亚段富有机质泥页岩层段虽具备良好的含气性,但却缺乏深入的含气特征系统分析。以盆地西缘南段地区为例,利用岩石地球化学、有机地球化学、同位素分析等多种分析手段,查明了该区三叠系延长组长7段烃源岩储层地质及地球化学特征,分析了长7段页岩含气性特征、页岩气赋存状态,初步计算了长7段页岩气资源量。研究区内三叠系延长组长7_(3)亚段黑色页岩含气性良好,其组成以页岩油溶解气为主,含少量干酪根黏土矿物吸附气及游离气,计算平均解吸气量为1.91 m^(3)/t。长7_(3)亚段赋存页岩油、气资源,二者资源量相当,在后期勘探开发研究中建议考虑油气并举的可能性。湖盆中部厚层长7段黑色页岩发育区含气量达2 m^(3)/t,储层刚性矿物及微孔裂隙发育,含气丰度高,资源量大,为页岩气有利勘探区域。初步计算长7页岩气总资源量约为4.25×10^(12) m^(3),具有良好的勘探前景,勘探有利地区为姬塬—固城—正宁一带。

基于机器学习的低含油饱和度砂岩储层参数预测——以准噶尔盆地夏子街油田夏77井区下克拉玛依组为例

准噶尔盆地夏子街油田夏77井区块下克拉玛依组(简称克下组)特低孔特低渗油藏油水关系复杂、产量低、储层含水高,且具有低含油饱和度、孔渗相关性差、储层参数与测井响应关系不清晰、油水层识别困难等特征,常规储层参数评价及预测方法适用性差。通过对岩性、物性、含油性分析,明确了克下组储层岩性为砂砾岩、砂质砾岩,黏土矿物以伊蒙混层为主;储层为以原生粒间孔和残余粒间孔为主要储集空间的低孔隙度、特低渗透率储集层。通过建立含油饱和度解释模型,确定了本区油藏属于低饱和度油藏,含油饱和度一般为36%~55%。砂砾岩储层物性和含油性优于中细砂岩,储层物性控制含油性,呈现低饱和度特征,电性受含油性和岩性双重影响。通过低含油饱和度油藏形成机理研究,认为储层微观孔隙结构是形成低含油饱和度的主要原因。通过对敏感参数优选,基于自然伽马、电阻率和声波时差测井等资料,引入基于机器学习的BP神经网络技术,对夏子街油田夏77井区块克下组油藏进行了孔隙度、渗透率和含水饱和度的计算及预测,储层参数预测精度均高于80%,相关结论及方法可为低含油饱和度致密砂岩储层的物性参数预测提供依据和参考。

鄂尔多斯盆地东南部三叠系长7油层组深水沉积特征及演化规律

以沉积学理论为指导,利用野外露头、钻井岩心、测井等资料,对鄂尔多斯盆地东南部三叠系长7油层组深水沉积特征包括相标志、沉积微相类型等进行了研究,并揭示了其沉积演化规律。研究结果表明:(1)鄂尔多斯盆地东南部三叠系长7油层组深水沉积的相标志包括:岩石中常见水平层理、鲍马序列、槽模沟模、滑动与滑塌构造、撕裂屑、泥包砾等沉积构造,含有深水双壳类和鱼类动物化石,粒度概率曲线中悬浮总体含量大且分选差,测井曲线上可见锯齿状、齿化箱形-钟形-指形、泥岩基线等特征。(2)研究区长7物源主要来自东北和南部2个方向,发育深湖—半深湖、湖底扇、浅湖沉积,湖底扇包括浊流和砂质碎屑流2种重力流类型,可进一步划分为重力流主水道、溢流沉积、重力流分支水道、分支水道间、朵叶体等微相。湖底扇主水道主要为砂质碎屑流沉积,分支水道和朵叶体主要为浊流沉积。(3)研究区长7沉积期,中南部主体发育深湖—半深湖、湖底扇沉积,东北部发育浅湖沉积;其中,东北方向发育4个湖底扇体,南部发育2个湖底扇体,半深湖/浅湖界线呈北西向延伸于延安—甘泉一带。长7^(3)亚段沉积期,深湖—半深湖范围最大,仅局部发育湖底扇;长7^(2)、长7^(1)亚段沉积期,湖底扇逐步增多,深湖—半深湖范围有所缩小,整体呈深湖—半深湖与湖底扇交互沉积态势。

基于碎屑岩储层孔喉特征的油水渗流微观解释——以桑塔木油田三叠系储层为例

为了对碎屑岩储层孔喉系统内油水两相渗流特征进行微观解释,通过对多口取芯井上真实岩心样品的薄片观察、压汞测试和相渗测试,以及对测试结果的统计学分析,发现研究区三叠系储层主要发育原生粒间孔,其孔隙结构类型有大孔粗喉型、大孔细喉型、中孔细喉型、小孔细喉型和微孔微喉型5种。特低渗、低渗、中渗、高渗和特高渗样品的顶点半径平均值依次为1.78μm,2.98μm,7.76μm,24.05μm和45.66μm,则正韵律储层在水驱油过程中,特低渗与低渗以及高渗与特高渗单元组合内的水相渗流阻力差别均为2倍左右,而低渗、中渗和高渗单元组合中的水相渗流阻力相差3倍左右。因此,可以通过储层中不同渗流能力的流动单元组合类型判断水相绕流程度的差异,进而确定绕流式剩余油的分布部位。

Isotopes (¹³C and ¹⁸O) Geochemistry of Lower Triassic Montney Formation, Northeastern British Columbia, Western Canada

Oxygen isotope (δ18O) serves as paleothermometer, and provides paleotemperature for carbonates. δ18O signature was used to estimate the temperature of fractionation of dolomite and calcite in Montney Formation, empirically calculated to have precipitated, between approximately 13°C to ±33°C during Triassic time in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). Measurements of stable isotopes (δ13C and δ18O) fractionation, supported by quantitative X-ray diffraction evidence, and whole-rock geochemical characterization of the Triassic Montney Formation indicates the presence of calcite, dolomite, magnesium, carbon and other elements. Results from isotopic signature obtained from bulk calcite and bulk dolomite from this study indicates depleted δ13CPDB (-2.18‰ to -8.46‰) and depleted δ18OPDB (-3.54‰ to -16.15‰), which is interpreted in relation to oxidation of organic matter during diagenesis. Diagenetic modification of dolomitized very fine-grained, silty-sandstone of the Montney Formation may have occurred in stages of progressive oxidation and reduction reactions involving chemical elements such as Fe, which manifest in mineral form as pyrite, particularly, during early burial diagenesis. Such mineralogical changes evident in this study from petrography and SEM, includes cementation, authigenic quartz overgrowth and mineral replacement involving calcite and dolomite, which are typical of diagenesis. High concentration of chemical elements in the Montney Formation?-Ca and Mg indicates dolomitization. It is interpreted herein, that calcite may have been precipitated into the interstitial pore space of the intergranular matrix of very fine-grained silty-sandstone of the Montney Formation as cement by a complex mechanism resulting in the interlocking of grains.

四川盆地中部磨溪气田中三叠统雷一1气藏储层特征及发育主控因素

为进一步明确四川盆地中部磨溪气田雷一1气藏的储层空间分布特征,以支撑该气藏下步的稳产挖潜和有利目标区域的优选,本文综合应用该气藏内65口取心井的岩心、11口井648个岩化分析、282块岩心的物性测试、416张铸体薄片、368个电镜扫描及82块高压压汞等资料,探究磨溪气田雷一1气藏储层特征及发育控制因素。结果表明:磨溪雷一1段储层发育于白云岩、灰质白云岩、砂屑云岩和云质灰岩中,储层主要分布于上亚段的中部、中亚段的底部和顶部;储层的储集空间类型多样,但以溶蚀作用形成的各类溶蚀孔隙为主;储层总体表现为中孔低渗的孔隙型储层,具有粗孔细喉、中孔微喉、微孔微喉等类型,但以中孔微喉和微孔微喉为主。储层发育主要受沉积作用、成岩作用及构造作用的控制。沉积过程形成的粗结构岩性的物性要好于细结构的岩性,胶结作用使先期形成的孔隙度减少了5%~95%,溶蚀作用使先期形成的孔隙空间增加3%~20%,白云化程度越高其物性较好。构造作用形成的低角度裂缝数量占绝对优势,未充填或部分充填的裂缝较完全被充填的裂缝多。未充填或部分充填的裂缝对储层发育的贡献较大,对储层的储集性能改善具有重要意义。

羌塘盆地中生代岩相古地理研究新进展

由于资料的欠缺和分布的不均衡,羌塘盆地构造-岩相古地理研究程度总体不高,不能为烃源岩和储层的分布预测提供依据。基于盆地属性、沉积体系及组合-耦合关系的研究,解决了资料丰富区域沉积相解释的多解性、资料缺少区域沉积相预测缺乏沉积模式指导的问题,取得以下3方面的成果和认识:(1)系统梳理了可可西里—金沙江洋、班公湖—怒江洋、龙木错-双湖洋的闭合史,明确了羌塘盆地属性,指出北羌塘地块在晚三叠世—早白垩世经历了复合前陆盆地、陆内弱挤压残留海盆地、褶皱-冲断快速抬升剥蚀3个构造演化阶段,南羌塘地块在晚三叠世—早白垩世经历了被动陆缘、活动陆缘、褶皱-冲断快速抬升剥蚀3个构造演化阶段,明确了8个关键沉积时期的盆地属性。(2)基于盆地属性、沉积体系及组合-耦合关系,系统恢复了羌塘盆地晚三叠世—早白垩世10个关键地质时期的构造-岩相古地理背景,揭示了构造对沉积的控制作用,提高了资料缺少区域沉积相预测的准确度。(3)明确了烃源岩和储层发育的构造-岩相古地理背景,认为上三叠统波里拉组—巴贡组烃源岩的分布受控于前陆坳陷、被动陆缘深水陆棚等构造单元,下侏罗统曲色组烃源岩的分布受控于弧后伸展盆地、陆内弱挤压残留海盆地等构造单元,中侏罗统布曲组白云岩储层分布于台缘带。上述成果将为羌塘盆地油气资源潜力的认识和评价提供依据。

资阳东峰场地区须家河组须五段气藏产能影响因素及稳产对策

针对四川盆地资阳东峰场地区上三叠统须家河组须五段气藏试采中表现出的单井天然气产能差异大、稳产效果差等问题,综合地质、动态监测、实验分析等资料,开展了产能主控因素及递减原因分析,提出了稳产对策。研究结果表明:①气井产能主要受井型和优质储层发育程度影响,水平井产能明显高于直井,优质储层越发育,气井产能越高;②气井稳产效果较差,稳产期平均为10个月,日产气量递减指数平均为0.0017,储层有效渗透率低、供气范围有限;③气井初期高配产带来大生产压差引发储层应力敏感伤害,地露压差小易析出凝析油造成储层反凝析伤害,使储层渗透率损失,导致气井产能迅速递减;④压裂砂回流使人工裂缝导流能力下降并在近井地带堆积造成砂堵,压裂液返排困难使气井积液甚至水淹,均会导致气井停产;⑤控压开采可有效降低储层渗透率的损伤,液氮助排、优化生产管柱有利于气井排液,延缓气井产能递减。该研究成果可以为类似地区致密砂岩气藏开发技术对策制订提供参考。

库车前陆盆地幕式冲断活动、层序-沉积响应特征及油气地质意义

综合利用野外露头剖面、钻井岩心、二维地震大剖面及重点区三维地震资料,建立库车前陆盆地三叠系构造-层序地层序列,探讨幕式冲断构造对沉积充填演化和烃源岩分布的控制作用。研究表明:①库车前陆盆地三叠纪的形成与发展经历了完整的强烈—减弱—松弛—宁静幕式冲断活动,与之对应可以划分4个二级层序(对应三叠系俄霍布拉克组、克拉玛依组、黄山街组、塔里奇克组)和11个三级层序(SQ1—SQ11),每个层序或层序内幕受次级幕式冲断构造活动影响,形成“下粗上细”的“二元”结构。②幕式冲断作用与区域层序序列、沉积充填以及烃源岩发育与分布具有明显的响应,幕式冲断作用初始强烈至宁静过程中,三叠纪自下而上的沉积演化呈扇三角洲—辫状河三角洲—湖泊—辫状河三角洲—曲流河三角洲沉积演化的特点,幕式冲断活动初始强烈—减弱期对应于厚层粗粒砂砾岩储层发育期,幕式冲断活动松弛—宁静期对应于烃源岩发育期。③受幕式冲断活动期次与强度控制,近东西走向逆冲断层下盘烃源岩不仅在黄山街组沉积时期明显沉积增厚,成为三叠系烃源岩发育中心,而且烃源岩软地层经历多期次的逆掩推覆,呈“叠垛式”堆积。(4)库车前陆盆地深层具备形成规模气藏的基础与条件,可以形成自生自储型岩性、下生上储型断块-岩性、地层不整合等多种类型的气藏,是未来天然气勘探规模增储建产的重要领域。

四川盆地须家河组坡折带发育特征及油气地质意义

前人针对断陷盆地坡折带开展了大量研究,但前陆盆地前渊向前缘隆起方向坡度较缓,大型构造欠发育,地形起伏小,坡折带研究较少。四川盆地晚三叠世须家河组四、五段沉积时期发育前陆盆地,学者们已关注到泸州—开江古隆起西侧川中—川西地区缓坡坡折带对沉积岩相的控制,但其他相关研究较少。通过对四川盆地地震反射剖面坡折带构造解释,结合区域地质已有成果,采用颗粒流数值模拟方法,厘清了川中—川西地区坡折带类型,以及坡折带与重力滑动构造之间的关系,分析了与重力滑动构造相关的新型油气圈闭特征。研究获得如下认识:(1)研究区发育断裂坡折带,以坡折带为界,东、西两侧各发育一套重力滑动形成的“前挤后拉”构造组合,构造变形强度弱于被动大陆边缘重力滑动构造;(2)研究区构造坡折带边缘断裂控制沉积相与砂体类型;(3)缓坡带重力滑动构造拉张区正断层下盘上升形成同沉积背斜发育的砂岩,与同期断陷内富有机质泥岩侧接,形成“旁生侧储”型油气藏;(4)陡坡带重力滑动形成的须五段同沉积背斜,被翼部泥岩以及滑动构造结束后沉积的泥岩所围限,形成源内砂体输导成藏;(5)与重力滑动构造相关的同沉积背斜油气藏是源内成藏新类型,研究区须五段可能存在平行坡折带NE向展布的此类油气藏。

东昆仑八宝山盆地上三叠统页岩气成藏地质条件分析

为探讨八宝山盆地上三叠统页岩气的成藏潜力,通过野外地质剖面测量、二维地震、调查井施工、录井、解析、样品采集及分析测试等工作,对研究区八宝山组的形成背景、泥页岩规模、生烃条件(TOC、Ro、有机质类型)、储集条件(矿物特征、储集空间、孔结构参数)、含气性、埋藏史和热演化史等进行研究。结果表明:①东昆仑八宝山盆地三叠纪以来经历了基底形成、断陷演化及隆升改造三个演化阶段,昆中、昆南断裂控制盆地沉积格局,在晚三叠世断陷期沉积滨浅湖、半深湖—深湖相的泥页岩夹砂岩、粉砂岩,受沉积相控制,自山前向盆地内泥页岩厚度逐渐增大,大部分地段累积厚度超过300 m,有效厚度在16.24~79.63 m之间,为八宝山组页岩气聚集成藏提供了物质基础;②井内714件样品的TOC含量分布在0.01%~49.14%,有机质类型以Ⅲ型为主,Ro在2.37%~3.45%,泥页岩有机质含量、热演化程度高,有机质类型好,生气条件优越;③八宝山组上段石英、黏土矿物含量平均为40.83%、46.06%;八宝山组下段石英、黏土矿物含量平均为39.62%、47.08%,与Barnett页岩、Marcellus页岩及四川盆地海相富有机质泥页岩相比,脆性矿物含量略低,黏土矿物含量稍高。八宝山组上、下段含气量平均为4.19 m^(3)/t、5.44 m^(3)/t,泥页岩中发育大量微裂缝、溶蚀孔隙、裂缝孔隙、粒间孔隙、有机质孔隙等,其比表面积、孔体积、孔径平均值分别为6.9403 m^②/g、0.0116 cm^(3)/g、8.5138 nm,有利于页岩气富集和吸附;④埋藏史、生烃史结果显示:八宝山盆地具有早期浅埋、中期深埋、晚期抬升的特点,上覆侏罗系羊曲组的硅质砾岩、碎屑岩及新生代沉积地层广泛分布,作为区域性盖层对页岩气藏起到了很好地封盖作用,综合研究认为八宝山盆地页岩气资源远景广阔。