Geochemical evidence of paleogeography and paleoclimate during deposition of the 2nd Member of Kongdian Formation in Kongnan area

The 2nd Member of Kongdian Formation has been made up of a large number of oil shale and mudstone in the Kongnan aera of Huanghua depression around the Bohai Bay.In the Kongnan area,the lake basins were very large and deep during the deposition of the 2nd Member of Kongdian Formation.During that period,the lakes were sealed,uncommunicated with the sea water and the paleoclimate was very warm and wet in Kongnan area.Analyzing the content of the trace element and the rare earth element,carbon and oxygen isotope in the disquisition,The authors prove the two views correct.

Reconsideration of the sediment characteristics of the second member of the Triassic Xujiahe Formation in Sanhuiba,Huaying Mountain

The second member of the Triassic Xujiahe Formation in the Sanhuiba area in Huaying Mountain is an important section of sedimentary delta facies in the Chongqing Tianfu Geological Survey and Training Base. In spite of some initial efforts on its lithology and lithofacies, the existing research is yet to be completed and suffers from contradictory conclusions and inadequate evidence. Starting from the sedimentary microfaeies types and cyclic features, we analyzed the vertical sequence of a sedimentary delta model and discovered that this section is a constructional delta deposit. Eight incomplete and asymmetric regressive cycles are marked off, given that frequent erosion surfaces appeared in the section. Based on the analysis of structural characteristics of every monocycle, we summarized the system of cycles, tracts and sequence characteristics of the overall section. In view of this systematic series of cycles, we discussed the features of the syndepositional tectonic movements in the area and conclude that, due to frequent erosion, migration and diversion of a sub-channel branch was brought about by oscillating movements of the crust. In a comparison with neighboring sections, we explored the cause of erosion and the relations between erosion and cycles. This study greatly strengthens existing research and theories, makes an important and comprehensive contribution to geological surveys and training in the area and provides essential suggestions for coal exploration, oil and gas evaluation and in general to exploration and development in the target stratum.

Geological characteristics and key exploration technologies of continental shale oil sweet spots: A case study of Member 2 of Kongdian Formation in the Cangdong sag in the Huanghua depression, Bohai Bay Basin

Under the general trend of stepping-up oil and gas exploration and development in China,the unconventional oil and gas resources such as shale oil and gas have become an important alternative.Abundant continental shale oil resources are developed in Member 2 of Kongdian Formation(Ek2)of the Cangdong sag in the Huanghua depression of the Bohai Bay Basin which has complex structure,strong heterogeneity,and large buried depth,thus,the geological characteristic of shale oil accumulation and key exploration technologies are investigated on base of the system coring of 635.8 m,centimeter-level fine description and analysis of over ten thousand samples,therefore,the“four accurate”technologies have been developed,including the accurate selection of sweet spot areas,accurate drilling of sweet spot layers,accurate fracturing of sweet spot layers and accurate measure of fracture-rich sections.The results show that the continental shale strata in Member 2 of Kongdian Formation can be divided into three types:felsic shale,limy dolomitic shale and mixed shale.The Member 2 of Kongdian Formation is characterized by diverse mineral components,abundant laminae,good source rocks and medium thermal evolution degree,tight reservoir with rich micropore and microfractures,high oil saturation and brittle mineral content,indicating good prospect of shale oil exploration.Through sedimentological study,TOC and Ro evaluation,brittle mineral calculation,and seismic fusion inversion,a total of 126 km^(2) of Class I sweet spots in Member 2 of Kongdian Formation was delineated comprehensively,which guides horizontal well deployment(Well GD1701H and Well GD1702H).The drilling rate of sweet spot of these two horizontal wells is up to 96%by tracing thin layer through fine calibration,locating compartment through fine inversion,ensuring window entry through precise positioning,and tracking sweet spot through adjustment.The “one-excellent and five-highs”criterion is used to select perforation points to realize differential designs of fracturing intervals and clusters.Micro-seismic and potentiometry monitoring show that the artificial fractures formed by volumetric fracturing are 300e400 m long and 120 m high,and control a volume of about 0.07 km^(3).The maximum daily oil production of two horizontal wells is 48 t and 66 t respectively to realize the economic exploitation of shale oil reserves controlled by fractures.The shale oil exploration in Member 2 of Kongdian Formation shows that the continental shale oil has great potential of exploration and development,and the above technologies are critical and effective for shale oil efficient recovery.

Micropore structure characteristics and quantitative characterization methods of lacustrine shale-A case study from the member 2 of Kongdian Formation, Cangdong sag, Bohai Bay Basin

To better understand the micropore characteristics of lacustrine shale and develop quantitative methodsfor characterizing lacustrine shale, the reservoir space types, structures and spatial distribution patternsof effective pores in the shale of Member 2 of Kongdian Formation in Cangdong sag are studied usingcores, thin sections, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM),nuclear magnetic resonance (NMR), whole-rock X-ray diffraction (XRD) data, etc. Various shale porositycalculation methods are evaluated. The study results show that the reservoir spaces of the shale mainlyinclude three types, i.e., matrix pores, organic pores and fractures. Flaky pore throats formed bydissolution-induced pores and mould pores can improve the pore connectivity. NMR effective porosity ofthe shale varies from 0.59% to 4.42% with an average of 2.38%, accounting for 49.54% of the total NMRporosity and 34.53% of the gas porosity. The shale is divided into the unimodal-type felsic shale, bimodaltype felsic shale, carbonate shale and mixed shale. The different lithologies exhibit linear correlationsamong NMR, gas and effective porosities. The shale has effective porosity of 0.56%-4.53% with an averageof 2.12%. Furthermore, the shale reservoir is divided into four classes: Class I reservoir with effectiveporosities of more than 2.5%;Class II1 reservoir with effective porosity of 2.0%-2.5%;Class II2 reservoirwith effective porosity of 1.5%-2%;and Class III reservoir with effective porosity of less than 1.5%.

莱州湾洼陷带浅层岩性油藏富集机理与亿吨级油田新发现——以垦利10-2油田为例

针对莱州湾凹陷深洼带浅层明下段油气成藏与富集机制不明的关键问题,利用钻测井、三维地震资料等综合分析,结合古环境、现代沉积类比、地球化学指标等分析,开展了砂体展布规律、油藏运聚模式研究,揭示了莱州湾凹陷洼陷带明下段沉积古环境与规模性砂体发育机制,建立了岩性油藏油气运移和大面积岩性油藏富集模式。研究表明:(1)明下段Ⅳ油组与Ⅴ油组水生草本植物占比高,化石丰度与分异度介于湖相与河流相之间,为典型的河湖交互沉积环境;测井曲线既有反映河流相砂体的正旋回特征、湖泊作用的反旋回特征,也有正、反复合旋回特征;受河流-湖泊沉积环境频繁交互、快速转换,共同组成了大面积展布、内部广泛连通的“枝蔓式”连片砂体。(2)油气经过陡坡带深层砂体中转站聚集,再通过边界油源断层运移至浅层,最后沿着浅层连片砂体向南部高部位运移;地化指标均具有长距离的运移效应,表现为“迂回式”的成藏特点。(3)明下段岩性油藏富集机制受控于连片砂体展布范围、砂体构型与泥岩封盖能力共同控制;油气先沿河道线状充注,再向湖漫砂体面状调整,形成了浅层砂体“先枝后蔓-枝蔓互联”的大面积连片含油场面;不同期次砂体构型差异控制油气富集程度,其中“枝蔓式”连片砂体保存能力优于孤立河道砂体,最大含油幅度可达117 m。新认识成功指导发现中国深洼带浅层首个大型高产岩性油田--垦利10-2油田,突破了被传统认定为渤海浅层勘探的“禁区”,开辟了渤海湾盆地深洼带浅层大型油田发现的新局面。

Analysis of lithofacies and evaluation of effective reservoirs of member 2 of Xujiahe Formation in the Xinchang area in Western Sichuan

In the Xinchang area in western Sichuan Basin,a total of 121.12 billion cubic meters of proved reserves of natural gas are discovered in Member 2 of Xujiahe Formation,but only 7.739 billion cubic meters of proved reserves of natural gas are produced.The main reason is that sandstones in Member 2 of Xujiahe Formation in the Xinchang area are generally tight,with strong heterogeneity,only intervals with relatively good physical properties have a certain production capacity;therefore,it is very necessary and important to evaluate effective reservoirs in Member 2 of Xujiahe Formation.Through analysis of cores,with consideration of color,sedimentary texture and grain size,lithofacies of Member 2 of Xujiahe Formation in the Xinchang area can be divided into 12 types.According to data of physical properties and thin section analysis,it can be concluded that the favorable lithofacies in the upper submember of Member 2 of Xujiahe Formation are the massive medium-coarse sandstone,the medium-coarse sandstone with cross bedding,and the medium-coarse sandstone with carbonaceous fragments.On the basis of electrical characteristics,well-logging interpretation standards for favorable lithofacies are established,in addition,favorable lithofacies and effective reservoir in the Xinchang area are determined,and distribution of favorable lithofacies(effective reservoir)is identified,which lay a solid foundation for next deployment of appraisal well and development of effective reserves.

榆林气田山西组2段砂岩成岩作用及孔隙演化

榆林气田主力气层山西组2段为一套辫状河三角洲沉积,储集岩主要为石英砂岩、岩屑石英砂岩。该储层砂岩是典型的低孔低渗储集岩。以岩芯观察为基础,结合对薄片鉴定、扫描电镜、阴极发光和物性等资料分析后认为,榆林气田山西组2段砂岩经历了压实作用、胶结作用、交代作用、溶解作用和粘土杂基的充填作用等多种成岩作用,目前已达到了晚成岩阶段A期。山2 段储集砂岩孔隙中,原生粒间残余孔隙占44.7% ,各类次生孔隙占5 5 .3% ,可见成岩作用是控制该区储层物性特征的一个关键因素。孔隙演化经历了原生孔隙的破坏、次生孔隙的形成和次生孔隙的破坏3个阶段,其中压实、胶结作用起主要破坏性作用。

鄂尔多斯盆地中东部山2段储集层岩性微观特征差异性的地质意义

通过大量薄片观察、扫描电镜、阴极发光等分析,并结合储集层物性、压汞等分析资料,研究鄂尔多斯盆地中东部山2段石英砂岩与岩屑砂岩微观储集特征的差异。石英砂岩石英含量高,杂基和软岩屑含量低,几乎不含长石;岩屑砂岩则石英含量低,杂基和软岩屑含量高,普遍含少量长石。根据石英砂岩与岩屑砂岩的石英颗粒表面特征的显著差异分析,石英砂岩是清水高能化学环境的沉积,沉积速率缓慢,具有以粒间孔为主的复合型孔隙组合,储集性好,勘探前景广阔;岩屑砂岩是混水低能、地表化学作用较弱环境的沉积,沉积埋藏作用迅速,孔隙发育差,仅见少量粒内溶孔,储集性差,勘探效益不明显。

鄂尔多斯盆地山2段砂岩储层的孔隙类型与孔隙结构

在铸体薄片鉴定、粒度分析、压汞曲线及物性分析统计的基础上,对鄂尔多斯盆地山2段砂岩储层的孔隙类型、孔隙结构等微观特征进行了深入分析,结果表明:山2段储集空间主要为粒间溶孔、原生残余粒间孔、岩屑粒内溶孔、杂基溶孔和高岭石晶间孔,局部发育微裂隙;渗透率随孔隙度的增大而增大,而孔隙度和渗透率的大小又与砂岩的孔隙结构有关。根据砂岩的压汞参数及物性特征,划分出4类储层:Ⅰ类——优质储层,主要发育粒间溶孔,具有较好的颗粒支撑,孔隙连通性好;Ⅱ类——较好储层,其储集空间为粒间溶孔—粒内溶孔—高岭石晶间孔组合;Ⅲ类——较差储层,主要发育残余粒间孔—高岭石晶间孔组合;Ⅳ类——差储层,仅发育孤立微孔。指出粗粒结构与含砾支撑结构的石英砂岩储层物性较好;含砾支撑结构储层具有双众数粒度分布特征,有利于孔隙水的流动,促进填隙物溶蚀和粒间溶孔的形成,使得储层的渗透率得到提高。

鄂尔多斯盆地延长油气区山西组山2段储层砂岩成岩作用

根据薄片、铸体薄片、扫描电镜、X-射线衍射及化验分析等资料,对延长油气区山2段储层的岩石学特征、成岩作用类型和阶段划分及其对孔隙的影响进行了研究。研究表明,该区山2段储层砂岩以石英砂岩、岩屑质石英砂岩为主,成分成熟度较高,结构成熟度较低。成岩作用类型主要包括:压实作用、胶结作用和溶蚀作用。砂岩经历了早成岩阶段A、B期和晚成岩阶段A1、A2和B期的成岩演化阶段。压实作用和胶结作用是砂岩孔隙度降低的主要原因,分别造成19.5%和14%的原生孔隙丧失;溶解作用形成的次生孔隙在一定程度上改善了砂岩储集性能,溶蚀作用增加的新孔隙平均为1.7%。

鄂尔多斯盆地长北气田山西组2段高分辨率层序构型与砂体预测

以钻井测井、岩芯描述和样品分析为基础,高分辨率层序分析为技术方法对鄂尔多斯盆地长北气田山西组2段进行了精细的沉积相和层序分析,将山2段确定为海相辫状河三角洲沉积体系,并将其划分为1个长期、2个中期、4个短期和9个超短期基准面旋回层序和2大类5种基准面旋回结构类型。分析了不同级别基准面旋回层序的叠加式样与砂体展布和演化规律,建立了以中期基准面升、降半旋回相域为等时地层单元的山2段地层格架和对单砂层进行了等时追踪对比,确定中期上升期是三角洲河道砂体连续叠置形成巨厚砂体的最有利时期,洪泛期为细粒沉积物沉积期,也是隔层和局域性盖层主要发育期,下降期受侵蚀影响河道砂体不发育。以高分辨率层序分析为基础,建立等时地层格架为约束条件,结合单砂体为等时地层单元编制砂岩等厚图、砂/泥比等值线图和沉积微相图,对长北气田山2段砂体分布开展序贯指示三维模拟和预测,为长北气田山2段气藏高效开发提供依据。

渤海湾盆地渤中坳陷渤中25-1油田古近系沙河街组沙二段沉积相及演化

渤中25-1油田位于渤海湾盆地渤中坳陷南部,其主力油层为古近系沙河街组沙二段。在岩心观察的基础上,结合测井、录井及地震资料综合分析,认为沙二段发育辫状河三角洲和湖泊2种沉积相类型;由于距离物源较远,研究区内主要发育辫状河三角洲前缘亚相和滨浅湖亚相。沙二段沉积时的古地貌北高南低,早期水体较浅,主要发育由西南部低洼处向东北部隆起区超覆的滨浅湖滩坝砂体;随着构造沉降、水体加深,来自西南物源的辫状河三角洲前缘砂体向东北方向不断推进,最终占据了研究区的主体,滩坝砂体则逐渐萎缩至消亡;沙二段沉积末期,研究区西部BZ25-1-1井区发生局部构造抬升遭受剥蚀,导致该井区完全缺失沙二段,周边井区也有不同程度的厚度缺失。

鄂尔多斯盆地东部山西组山2段储层孔隙类型及成因分析

研究了鄂尔多斯盆地东部上古生界山西组山2段储层的孔隙类型和次生孔隙成因。其结果显示山2段储集空间以残余原生粒间孔和溶蚀孔为主。电子探针分析表明,被溶蚀物质主要为杂基和假杂基,溶蚀作用的强弱受岩石类型和沉积作用等条件的影响。在靠近湖盆生烃中心的三角洲砂体中,溶蚀作用强,孔隙发育。

川西坳陷T_3x^(1～2)油气成藏期研究

以烃源岩演化过程中各阶段的最大古地温和最大埋深为基础,结合实钻资料,首先确立了川西坳陷中段上三叠统须一、须二段含油气系统不同地区烃源岩的生烃阶段和排烃阶段,再利用计算的不同生排烃阶段的生、排烃量,砂岩、泥岩孔隙度变化和油气成藏之间的关系,最终认为不同地区油气成藏的主要时期都为晚三叠世中期,从而为确定川西坳陷中段上三叠统须一、须二段含油气系统圈闭的有利时期指明了方向。

东胜气田锦66井区盒2+3段地层水特征及地质意义

通过对东胜气田锦66井区盒2+3段地层水主要化学特征参数分析,揭示了锦66井区盒2+3段地层水的化学性质与气藏储层之间的内在联系。研究表明:东胜气田锦66井区盒2+3段正常地层水的判断标准为矿化度≥25000 mg/L、钠氯系数﹤0.4、钠钙系数﹤2.3、压裂液返排率≥55%;盒2+3段地层水为氯化钙水型,整体为高矿化度弱酸性盐水–卤水;储层封闭性良好,非常有利于天然气的富集保存;储层以次生孔隙为主,物性差异较大、连通性较差。

鄂尔多斯盆地东部山西组山2段胶结物特征及其对储层物性的影响

鄂尔多斯盆地东部山西组山2段是天然气勘探的重点层位,山西组山2段具有较强的非均质性,胶结物是影响非均质性的主要因素,因此开展山2段胶结物特征及其对储层物性影响的研究具有重要意义。通过铸体薄片、扫描电镜、荧光薄片、阴极发光和X衍射黏土矿物分析等测试手段对山西组山2段胶结物特征及其对储层物性的影响进行了研究。结果表明:研究区山2段储层胶结物主要为伊利石、碳酸盐胶结物、硅质胶结物、高岭石;通过对胶结物特征和与储层物性的关系研究,发现高岭石和少量的硅质胶结物是储层物性的有利因素,伊利石、碳酸盐胶结物及较多含量的硅质胶结物使储层致密化,对储层孔隙发育不利。

伊拉克哈法亚油田Mishrif组MB1-2亚段局限台地碳酸盐岩储层特征及评价

伊拉克南部哈法亚油田Mishrif组广泛发育碳酸盐岩局限台地沉积。基于岩心、薄片资料,分析Mishrif组MB1-2亚段碳酸盐岩局限台地沉积微相、岩性与孔隙发育特征,研究碳酸盐岩储层特征。结果表明:储层总体上具有相控性,沉积微相对储层起主要控制作用,可分为生屑滩相储层、潮道相储层及潟湖相储层,储集空间主要分为微孔、晶间孔、粒内溶孔、铸模孔、粒间溶孔、溶蚀孔洞、粒间孔、体腔孔和生物格架孔。颗粒灰岩储集性最好,泥晶灰岩储集性最差,储集性同时受孔隙类型与成岩作用类型控制。该结果为哈法亚油田油藏挖潜和开发策略制定提供指导。

赤岸油田韦2断块阜一段高分辨率层序地层学研究

以高分辨率层序地层学理论方法为指导,综合运用岩心、录井和测井等资料,对赤岸油田韦2断块阜宁组一段进行了高分辨率层序地层学研究。结果表明,该区阜一段由4个中期基准面旋回层序组成,并划分出17个短期基准面旋回层序,其中短期旋回层序以向上"变浅"的非对称型和对称型2种基本结构类型为主;在各级次基准面旋回划分的基础上,应用旋回等时对比技术进行了精细地层对比,建立了韦2断块阜一段高分辨率等时地层对比格架。该研究为进一步的储层物性预测及储层结构描述等精细地质研究奠定了基础。

断陷湖盆细粒区页岩组构特征与页岩油富集成藏规律:以黄骅坳陷古近系为例

为明确断陷湖盆细粒区页岩微观组构特征及页岩油富集成藏规律,基于黄骅坳陷古近系孔二段、沙三段、沙一段3套页岩层系取心、测井、录井及试油等资料,综合利用矿物分析-场发射扫描电镜、氩离子抛光-场发射扫描电镜、聚焦离子束-场发射扫描电镜等技术手段,针对页岩样品开展多尺度、多维度精细表征,从微观、定量的角度系统分析了页岩矿物、有机质、孔隙及页岩油赋存特征,揭示了页岩油成藏富集规律并建立了富集模式。研究结果表明:在微观视域下,多类型矿物以“组分混合”和“组构叠置”构成复杂页岩类型;储集空间可划分为无机孔隙、有机孔隙和微裂缝3大类9小类,其中无机孔隙贡献率平均可达85%以上,孔径<50 nm的孔隙占据储集空间的主体;微观上有机质可划分为同沉积有机质、交生分异有机质和运移充填有机质3种类型;烃类主要赋存于长英质纹层、灰云质纹层或粉砂岩纹层中。基于矿物、有机质、储集空间、烃类4个要素的“四元耦合”页岩油富集成藏规律,建立了3类富集成藏模式。在该模式指导下,沧东凹陷孔二段实施多口水平井获高产,优质页岩油区块已经实现当今油价下的效益开发,歧口凹陷沙三段及沙一下亚段页岩油均获得重要突破,展示出黄骅坳陷古近系页岩油具有广阔的资源前景。

秦皇岛29-2油田与米桑油田的混合沉积储层对比

对比我国秦皇岛29-2油田与伊拉克米桑油田的储层岩性、储集空间、沉积模式等特征。秦皇岛29-2油田与米桑油田均发育混合沉积,前者发育湖相混合沉积,后者发育海相混合沉积。这两类沉积储层都具有岩性复杂多样、物性差异大的特点,且储集空间均以次生溶蚀孔隙为主,残余原生孔隙度不高,部分颗粒间有少量原生孔隙在一定条件下得以完好保存。二者储层岩性的差异在于:秦皇岛29-2油田的沙二段储层厚度变化大且规模有限,主要优质储层为生屑云岩层;米桑油田的储层厚度稳定且分布广泛,主要优质储层为含石英砂岩层。其储集空间的差异在于:秦皇岛29-2油田沙二段受到淡水淋滤作用;米桑油田Asmari组在构造作用下形成大量微裂缝,扩大了储集空间,加大了储层的连通性。构造作用、沉积物源供给的差异导致了两油田储层规模和分布特征的差异。