The source and formation characteristics of the Zhujiadun gas reservoirs in the Yancheng Sag, Subei Basin

The Yancheng Sag is a favorable exploration area in the Subei Basin. However, the key geological understanding of the natural gas source and reservoir formation characteristics of the sag is still controversial. Based on a set of organic geochemical experiments conducted on natural gas and associated condensate oil of the first member of the Funing Formation (E1f1) in well YCh5 and well data analysis, the oil-gas resources and reservoir formation model in the Zhujiadun gas reservoir in the Yancheng Sag, Subei Basin, were investigated. The results of this study are as follows. (1) The natural gas in the Zhujiadun gas reservoir is dry gas with high methane content, low heavy hydrocarbon content, and high maturity. The characteristics of carbon and hydrogen isotopes in the natural gas indicate that the natural gas is oil-cracked gas, which mainly originates from the source rocks of the Permian Qixia Formation. (2) The condensate oil from well YCh5 with a high degree of maturity has a high pristane/phytane ratio, low gamma-paraffin abundance, and low tricyclic terpene abundance, indicating a mixture of the Upper Paleozoic condensate oil and Cenozoic crude oil. The saturated and aromatic hydrocarbons have similar δ13C values to the Cenozoic continental crude oil. These features suggest two sources of condensate oil. (3) Oils generated from the source rocks of the Qixia Formation were cracked into highly mature gas after deep burial, which migrated along large faults into the sandstones of the E1f1 and K1t1 members. This type of reservoir was effectively preserved beneath the overlying mudstone cap rocks. Therefore, it can be inferred that a play fairway might occur in the eastern zone of the faults connected to the Paleozoic source rocks in the Yancheng Sag since this zone has similar petroleum geological conditions to well YCh5. Therefore, this zone is a favorable area for further exploration.

Sedimentary Evolution and Transgressions of the Western Subei Basin in Eastern China since the Late Pliocene

Sedimentary sequences in the Subei Basin are complex and have been affected by interactions between the ocean and rivers since the Late Pliocene, including the Yellow River, Huaihe River, and the Yangtze River. This sedimentary evolution, in particular the timing of Pleistocene transgressions, has long been a matter of controversy owing to the lack of precise chronological evidence. The aim of this study is to explore the evolution of the sedimentary environment throughout the past 3.00 Ma in this region on the basis of a comprehensive analysis of particle size and foraminifera and ostracods collected in the TZK9 core from the Subei Basin combined with geochronological studies of magnetostratigraphy, AMS^(14)C and optically stimulated luminescence(OSL). The results show that fluvial facies in the sedimentary environment from 3.00 to 1.01 Ma. There were fluvial facies and reflects six sea-level high stands from 1.01 to 0.25 Ma. The study area was affected by four large-scale transgressions since 0.25 Ma. The four marine sedimentary layers known as DU7(buried at 48–52 m), DU5(buried at 35–41 m), DU3(buried at 16–23 m), and DU1(buried at 2–4 m) are recorded in the MIS7(210–250 ka), MIS5, MIS3, and Holocene, respectively. The magnitude of the DU5 transgression was identical to that of the DU3 transgression, both were larger than the DU7 transgression, and the DU1 transgression was the weakest. The variation of transgression strength reflects the influence of global changes in sea level, tectonic subsidence, shell ridges, and sand dams. In the TZK9 core, we found evidence of seven sea-level high stands from the Early–Middle Pleistocene, and the first one caused by regional rapid subsidence and could be traced back to 0.83-0.84 Ma. The sea-level high stands and the age of the first one recorded above was different from other cores in eastern China, this was caused by the lack of absolute age control and the differences in paleotopography during this period. This study reconstructs sedimentary evolution, determines the transgression and its age, establishes the chronology since the Late Pliocene, and provides a scientific framework for further paleoenvironmental and tectonic studies. The results of this study highlight the important role that local tectonics and global sea level play in the sedimentary evolution and transgressions that have occurred in the western Subei Basin.

Exploration Strategies for Complex Fault Block Reservoirs in the Subei Basin

The geological background of the Subei basin is that of small relief subsidence, low geothermal gradient, multi-sedimentary hiatuses, intense reconstruction of the basin, frequent magmatic activity, and a unique combination of source rock and reservoir. This geological background resulted in characteristics such as many small fault blocks, multiple oil-bearing formations, scattered oil distribution, mini- to small-sized reservoirs, and difficulties in exploration. Aimed at such characteristics, an effective exploration strategy was adopted, and the oil reserves, production and economic benefits of the Jiangsu oilfield were significantly increased. This exploration strategy included understanding the hydrocarbon generation mechanism of source rocks, progressive evaluation of oil resources, comprehensive research on the faulted systems, the distribution of oil reservoirs and their controlling factors. The techniques used included integration of acquisition, processing and interpretation with 3-D seismics as the core technology, trap description and evaluation, directional drilling and cluster drilling, integration of cuttings logging, gas chromatographic logging and geochemical logging, and integration of early reservoir description and progressive exploration and development. This strategy could be guidance for other complex fault blocks.

Estimation of the amount of erosion at unconformities in the last stage of the Eocene Sanduo period in the Subei Basin,China

Strata erosion is a widespread phenomenon in sedimentary basins. The generation, migration, and accumulation of hydrocarbon is influenced by the scale of erosion, so estimating the amount of erosion is essential in the analysis of oil and gas bearing basins. According to the geological features in the Subei Basin and the actual data, using the integrated method, we estimated the level of erosion at the unconformities caused by the Sanduo event. By using the mudstone interval transit time method and the vitrinite reflectance method on data from typical wells, it can be concluded that the Gaoyou, Jinhu, and Hongze depressions suffered strong strata erosion from the late Eocene to Oligocene, and the total strata erosion thickness was 300–1,100 m. Different tectonic units in the same depression have extremely uneven erosion intensity: the low convex regions have the maximum erosion thickness, amounting to 800–1,100 m; the slope regions have an erosion thickness of generally 600–800 m; the erosion thickness of the slope-hollow transition zone is 300–500 m. For the whole basin, we used the strata thickness trend analysis method combined with the interval transit time and vitrinite reflectance methods to estimate the erosion thickness in the Sanduo period. The results show that the most severe erosion of the Sanduo event in the Subei Basin is between 1,000 m to 1,200 m, mainly located in depressions around the Jianhu Uplift; the deep hollow area has the least erosion, generally about 300–600 m, and the erosion in the slope area is about 600–900 m. Compared with the northern part, the southern part has relatively little erosion. It is also proved that the Sanduo movement has heterogeneous intensity, and the western region has greater intensity than the eastern region.

Paleoclimatic and provenance implications of magnetic parameters from the Miocene sediments in the Subei Basin

Thick sediments from foreland basins usually provide valuable information for understanding the relationships between mountain building,rock denudation,and sediment deposition.In this paper,we report environmental magnetic measurements performed on the Miocene sediments in the Subei Basin,northeastern Tibetan Plateau.Our results show two different patterns.First,the bulk susceptibility and SIRM,ARM,and HIRM mainly reflect the absolute-concentration of magnetic minerals;all have increased remarkably since 13.7 Ma,related to provenance change rather than climate change.Second,the ratios of IRM100mT/SIRM,IRM100mT/IRM30mT,and IRM100mT/IRM60mT,together with the redness and S ratio,reflect the relative-concentration of hematite,being climate-dependent.Their vertical changes correlate in general with the long-term Miocene climatic records of marine oxygen isotope variations,marked by the existence of higher ratios between 17 and 14 Ma.This may imply that global climate change,rather than uplift of the Tibetan Plateau,played a dominant role in the long-term climatic evolution of the Subei area from the early to middle Miocene.

加权断层泥比率法(WSGR)定量判别断层封闭性——以苏北盆地高邮凹陷永安地区为例

断层封闭性评价是断块圈闭成藏条件分析的重要内容,在改进断层泥比率法基础上,提出了一种新的断层封闭性评价方法——加权断层泥比率法(WSGR)。首先,通过不同的地质模型开展断层泥比率法计算参数及影响因素分析,明确了断层断距、泥质含量及泥岩分布特征是泥岩涂抹的重要影响因素;并认为断层断距范围内,滑过目标位置的对置盘所有泥质含量都具有涂抹贡献,但不同点的涂抹贡献不同,距离目标位置越近泥质含量越高的对置盘泥岩点,其涂抹贡献越大。为此引入了一个新的表征参数——距离系数,定义为断层断距与各泥岩点到目标位置距离的差与断层断距的比值,来表征泥岩分布对泥岩涂抹的影响作用;在此基础上,构建了加权断层泥比率计算方法,定义为各点的泥质含量与距离系数的乘积之和再与距离系数之和的比值。利用加权断层泥比率法对苏北盆地高邮凹陷上含油气系统已知的油水层进行封闭性验证,认为当加权断层泥比率值大于0.6时,断层具有较好的封闭性,从而确定了该方法的封闭性判别标准。在高邮凹陷永安等地区始新统戴南组断层封闭性评价中取得了较好应用效果。

陆相页岩油储层可动油含量测井评价方法——以苏北盆地古近系阜宁组二段页岩油为例

近年来中国东部陆相盆地页岩油勘探开发取得重大进展,但制约页岩油产能评价的关键因素是油可动性。研究苏北盆地页岩油提出了二维核磁共振法和常规测井法2种测井评价页岩可动油含量的方法。建立了二维核磁共振测量纵向弛豫时间(T1)-横向弛豫时间(T2)可动油识别图版,评价吸附油及束缚水等流体类型,通过游离烃含量(S1)与沉积环境、沉积构造的关系及测井响应的关联性,分析常规测井电阻率及声波时差对游离烃含量、有机质含量响应灵敏度,建立了游离烃含量测井定量评价模型。提出了测井资料评价游离烃含量的方法,计算可动油饱和度及含油量。咸化环境和纹层状构造有利于有机质成烃和运移,游离烃含量高。

苏北盆地古近系阜宁组二段页岩油储集空间特征及甜点段评价——以溱潼凹陷QY1井为例

苏北盆地古近系阜宁组二段是常规油重点产层,同时也是中国东部陆相页岩油勘探开发的优选层位。对溱潼凹陷QY1井岩心样品进行分析测试表明,该套页岩具有低有机质丰度、较低镜质体反射率(R_(o))、矿物组分均衡及孔隙网络复杂的特点;运用岩石学及地球化学方法等对该页岩油储层的岩相特征、储集空间特征、含油性与可动性、脆性指数与可压性特征等进行研究,指明了生产甜点段。阜二段是一套混积页岩纹层型储层,矿物组成以黏土、长英质和碳酸盐矿物为主,有机碳含量平均值为1.32%,R_(o)为0.9%~1.1%;平均孔隙度中下部为4%,上部为2.2%。根据“有机质丰度+构造特征+岩性”将阜二段页岩划分为6种岩相,其储集性具有明显差异,纹层发育特征的差异是导致不同岩相具有不同储集空间特征的重要原因。除低有机质纹层/层状灰云质页岩外,其他岩相都具有较好的含油性;高有机质层状灰质页岩的有机碳含量最高。纹层数量与油气可动性具有较好的对应性,从中有机质纹层状含灰云页岩到高有机质块状泥岩,平均含油饱和度指数从202.62 mg/g降至77.83 mg/g。高有机质块状泥岩由于存在大量塑性矿物,造缝效果是6种岩相中最差的。中有机质纹层状含灰云页岩是最优岩相,中有机质层状含灰云页岩和中有机质纹层/层状灰云质页岩略差,但也可以作为优势岩相成为勘探开发的重点。根据优势岩相在纵向上的分布,优选阜二段Ⅰ亚段③—⑤小层和Ⅱ亚段②—④小层为该区地质甜点段。

苏北盆地溱潼凹陷阜宁组二段页岩油测井评价研究

如何利用常规测井资料对储层含油性、储集性及可压性进行有效评价,是苏北页岩油规模化开发亟需解决的生产难题。利用常规测井资料与岩心实验资料,采用最优化、拟合、正反演数值模拟等数学手段,建立起总有机碳含量、有效孔隙度、层理缝密度、矿物组分含量等参数的计算模型,对页岩沉积构造和岩相进行分类研究。研究表明:溱潼凹陷阜宁组二段(以下简称阜二段)泥页岩以富有机质层状或纹层状泥岩、富有机质块状泥岩为主,有利岩相为富有机质层状或纹层状泥岩,有利岩相纵向上与非有利岩相交互出现。采用文中所导出的模型识别的“甜点”层段与采用特殊测井分析的层段位置具有良好的一致性,且现场应用效果良好。该方法和技术已应用于苏北盆地页岩油储层地质工程“甜点”段的选定工作,对苏北页岩油效益开发具有重要意义。

高邮凹陷花庄地区页岩油二维核磁测井评价应用

苏北盆地高邮凹陷古近系阜宁组二段泥页岩具有孔隙结构复杂、层理发育、非均质性强的特点,应用常规测井系列难以准确评价孔隙及流体类型,二维核磁共振测井在流体识别方面具有独特优势。应用“盲源分离”信号处理技术进行数据聚类分析,通过花庄地区流体分区模型识别出地层中不同赋存状态的流体及含量。研究结果表明:二维核磁测井提高了储层流体评价精度,提供较为可靠的总孔隙度、有效孔隙度、含油饱和度、可动油含量等参数,通过与岩心实验分析对比,有效孔隙度平均绝对误差为0.4%,含油饱和度平均绝对误差为7.3%。通过阜宁组二段泥页岩主要岩性中流体性质分析,表明长英质灰云质混积页岩在物性、含油性、可动性方面最优,是页岩油优质“甜点”层。花庄地区应用二维核磁测井能够有效地解决页岩油孔隙度、饱和度评价的难题,也能为页岩油“甜点”优选、储层产能预测提供参考。

苏北盆地古近系阜宁组二段页岩油储层岩石力学特征及其控制因素

为查明苏北盆地页岩油储层可压性特征及压后孔、缝变化规律,以古近系阜宁组二段(阜二段)为研究对象,对岩石力学特征、压裂效果及其影响因素进行研究。用计算机高分辨断层扫描成像技术(多尺度CT扫描)对岩样进行三维重构,获取孔、缝结构参数;开展地层围压下三轴力学实验,获取岩石力学参数;将压裂后的岩样按相同位置和方向再次进行多尺度CT扫描,获取压裂后三维孔、缝结构图像。根据应力-应变曲线特征,将本区页岩划分为3种类型。①1型页岩,为破裂曲线波浪下降,压后形成复杂网状缝页岩。②2型页岩,为破裂曲线类型多样,具波浪下降和垂直下降形状,压后缝网较发育的页岩。③3型页岩,为破裂曲线垂直下降,破裂后整体较完整,压后多形成纵向劈裂缝、缝网不发育的页岩。这3种类型页岩压后孔隙变化特征是:1型和2型页岩直径10~50μm孔隙占比减少,直径50~100μm孔隙增多,直径300μm以上孔隙孔容贡献增大;3型页岩压裂前、后孔径分布及孔容贡献变化不明显。研究表明,抗压强度与弹性模量、剪切模量具有正相关关系,与泊松比具有V型曲线关系;碳酸盐和黏土矿物含量是控制本区页岩力学性质的主要因素,石英和有机碳含量为次要因素。孔隙度及纹层发育特征是页岩储层可压性特征的重要影响因素。

苏北盆地黄桥地区盐城组氦气成藏地质条件及富集规律

苏北盆地黄桥地区新近系盐城组天然气中He含量介于1.05%~1.40%,普遍高于工业品位,为壳—幔复合型氦气资源。目前,对于这种来源的氦气富集主控因素以及勘探目标评价的研究较为薄弱,为此,系统剖析了黄桥地区典型富氦气藏氦气成因、来源及圈闭特征,重点分析了幔源断裂对富氦气藏输导作用、盐城组圈闭条件的影响,提出了黄桥地区盐城组富氦气藏富集模式。结果表明:(1)黄桥地区南新街深大断裂在盐城组沉积时期持续活动,导致幔源物质上涌,伴随着火山活动及CO_(2)、N_(2)以及氦气沿断裂运移至浅层;(2)黄桥地区盐城组埋深为370~400 m,盐城组底部砂岩厚度约为40 m,上覆10~40 m泥岩,储盖组合有利,富氦气层由东往西尖灭;(3)黄桥地区盐城组整体为单斜构造,盐城组底部界面与下伏地层呈角度不整合,通过地震标定及解释,刻画出了富氦气层岩性—地层复合圈闭面积。黄桥地区盐城组富氦气藏具有断裂沟通地幔输导、砂岩储集、泥岩作为盖层、岩性—地层复合圈闭富集等特征,该认识对黄桥地区氦气有利目标评价具有重要意义。

陆相页岩油水平井开发合理生产制度优化——以苏北盆地A区块阜二段为例

为了最大限度提高陆相页岩油全生命周期的采收率,并建立其水平井开发的合理生产制度。选取苏北盆地A区块阜二段为靶区,利用井震资料开展储层发育特征研究,建立“地质—开发—地应力—裂缝扩展”的地质工程一体化模型,进而对页岩油水平井开发合理生产制度进行优化研究。研究结果表明岩石类型、裂缝分布、岩石力学参数和工程施工参数是影响页岩油地质工程一体化模型精度的关键因素,确定了压后合理开井时间为20 d、合理生产压差为10 MPa、CO_(2)合理吞吐时机为井口压力下降至1.5 MPa左右、CO_(2)合理吞吐焖井时间为15 d,形成了页岩油水平井开发合理生产制度优化流程。研究成果对陆相页岩油长期稳产和效益开发具有重要支撑作用。

苏北盆地高邮凹陷阜二段页岩储层裂缝发育特征及有利勘探区评价与预测

针对页岩储层天然裂缝发育有利区难以合理预测的问题,以岩心、薄片、成像测井等资料为基础,开展储层天然裂缝成因类型、发育特征及主控因素评价。结果表明:高邮凹陷阜二段主要发育构造裂缝和层理缝,部分岩心可观察到同沉积裂缝、肠状裂缝和超压裂缝;其中构造裂缝以高角度有效缝为主,交叉节点类型主要为Y形和X形,节点数量(C_(L))多数处于2.00~3.57,裂缝处于连通状态并且连通性较好;构造裂缝和层理缝中含油性较好,验证了裂缝对页岩油气存储和输导的重要作用;构造裂缝主要受主干断层发育及地层褶皱影响,距离主干断层越近,裂缝发育密度越高;地层弯曲度越大,裂缝发育密度越高;层理缝主要受生烃增压影响,与局部高w(TOC)地层的超压发育关系密切;据此预测高邮凹陷阜二段页岩储层构造裂缝发育Ⅰ类有利区4个、Ⅱ类有利区4个,层理缝发育Ⅰ类有利区2个、Ⅱ类有利区4个,预测结果有效指导了该区页岩油气勘探开发工作。研究成果可为页岩储层天然裂缝预测奠定基础并提供参考依据。

苏北盆地高邮凹陷古近系阜宁组二段页岩油富集主控因素

高邮凹陷古近系阜宁组二段是苏北盆地页岩油勘探的重点区带和层系,已部署实施的8口页岩油水平井的成功,证实其具有非常大的页岩油勘探潜力和良好的勘探前景。针对该层段页岩油井产能存在差异、富集主控因素认识不清楚等难点问题,综合利用岩心、测录井、分析测试数据和生产动态数据等资料,对阜二段地质特征和页岩油富集主控因素进行研究。高邮凹陷阜二段泥页岩以长英质—黏土质混积岩和长英质—灰质/白云质混积岩为主,有机质丰度中等,有机质类型以Ⅰ型和Ⅱ1型为主;自下向上有机质类型由腐殖型向腐泥型逐渐转变,有机质丰度总体由低逐渐增高,具有较好的页岩油形成条件。综合岩相、生油性、含油性、储集性、可压性等多因素评价可知,高邮凹陷阜二段共发育Ⅴ-4~Ⅴ-9、Ⅳ-2~Ⅳ-7小层和Ⅱ~Ⅲ亚段三套勘探有利层段。阜二段页岩油富集具体表现为:①有利岩相组合是页岩油富集的物质基础,其中混积岩夹白云石条带是有利的源—储配置组合,页岩油产能高;②复杂的孔缝系统是页岩油富集的核心,层理缝和裂缝是页岩油流动的主要通道,有效沟通基质孔隙,提高页岩油导流能力;③较高的成熟度和良好的保存条件是页岩油高产稳产的关键,镜质体反射率(R_(o))介于0.8%~0.9%时滞留油含量相对较高,远离长期活动性断层的井游离烃含量(S1)相对较高。

苏北盆地溱潼凹陷古新统阜宁组二段侵入岩围岩变质带储层特征及其成藏意义

火山岩油气藏是油气勘探的重要领域之一。苏北盆地溱潼凹陷侵入岩分布广泛,油气显示活跃,已成为我国东部陆相盆地油气深化勘探和规模增储的重要领域,具备良好的勘探前景。然而,目前针对火山岩对泥页岩围岩储层及其成藏影响的研究较为缺乏,泥页岩围岩变质带能否作为勘探重点领域有待深入评价。为了推动苏北盆地侵入岩围岩变质带新类型油藏勘探,以溱潼凹陷阜二段侵入岩围岩变质带为研究对象,综合岩心、薄片、全岩、测井等资料,系统揭示了泥页岩变质带储层特征,明确了岩浆侵入对阜二段变质带油气成藏的贡献。研究表明,溱潼凹陷阜二段泥页岩受岩浆侵入影响,泥页岩围岩发生蚀变形成环状变质带储层,岩浆的侵入具有明显“增储作用”;变质带储层发育孔隙、裂缝两类储集空间,储层发育程度受侵入岩厚度及烘烤强度控制,岩浆的侵入具有“催熟作用”,同等深度下泥页岩Ro可增加0.4%~0.5%;阜宁组侵入岩形成于吴堡期—三垛期,火成岩侵入形成环状变质带的时间早于油气充注期,具有良好的成藏匹配关系。受岩浆侵入、侵入岩空间分布以及源储匹配关系控制,溱潼凹陷阜二段侵入岩围岩变质带具有源储一体、近源富集的特征,是规模增储的新阵地。

高邮凹陷花庄地区阜二段页岩储层孔喉结构特征研究

高邮凹陷深凹-内坡带花庄地区阜二段(E_(1)f_(2))是苏北盆地页岩油勘探的有利地区和层段,为进一步明确花庄地区E_(1)f_(2)页岩储层特征,以有利区内系统取心井HY1井为依托,通过岩心观察,运用薄片鉴定、氩离子剖光-扫描电镜、高压压汞、氮气吸附以及核磁共振等多种方法联合精细表征页岩孔隙结构,分析了HY1井E_(1)f_(2)取心页岩段页岩的孔隙度、孔隙类型及连通性、孔喉特征、全尺度孔径大小等。研究表明,花庄地区E_(1)f_(2)发育3类10种孔隙类型,以无机孔为主;其中纹层状长英质灰云质混积页岩和灰云页岩孔隙度相对较大,碳酸盐岩粒间(内)孔和颗粒边缘孔更为发育,孔隙多为H2-H3型和H3型,连通性较好,喉道相对略大,孔隙结构呈三峰特征,中-大孔占比较高,孔径主体分布大于100 nm,储层条件最为有利,其发育层段可作为高邮凹陷花庄地区阜二段页岩油勘探“甜点”层之一。

基于ANSYS FLUENT的自喷页岩油井液量标定研究

华东油气田苏北盆地页岩油井在经过水力压裂后,投产初期的大液量、高液温、高气油比等特征均对油井的液量标定带来一定困难,现有的液量标定方式均无法满足现场液量标定要求。利用三维软件建模,导入ANSYS FLUENT中进行数值模拟,通过模拟地面油嘴前后部分流程,进行液量影响因素分析,明确节流前压力、节流后压力、油嘴直径、含水率为产液量主控因素,并对其进行权重分析,然后将数值模拟结果进行数学回归,得到关于自喷页岩油井液量的数学模型。将数学模型与矿场数据相对比,数学模型能够很好地反映生产参数、生产制度变化后的液量变化,对矿场自喷页岩油井的液量标定有一定的指导意义,能够有效提高液量标定准确度、降低现场劳动强度。

苏北盆地高邮凹陷阜二段页岩天然裂缝发育特征及其对页岩油富集和保存的影响

苏北盆地高邮凹陷古近系阜宁组二段(阜二段)页岩油勘探获得重大突破,是下一步增储上产的重要领域。页岩层系中天然裂缝发育复杂,其对页岩油富集和保存的影响认识不清,制约了下一步勘探部署。综合来自HY1、H101、HY7、S85X等井的岩心、录井、测井和镜下薄片、扫描电镜、大视域扫描电镜拼接(Maps)、微区矿物扫描(Qemscan)、冷冻岩心有机地球化学分析等资料,结合HY1HF、HY3HF等井的生产动态资料,系统分析了阜二段页岩层系中天然裂缝发育特征,进一步揭示了不同类型天然裂缝对页岩油富集和保存的影响。结果表明,阜二段页岩层系主要发育穿层构造裂缝和层控构造裂缝,以及层理缝和收缩缝等非构造裂缝。其中,穿层构造裂缝发育程度与岩性及构造部位密切相关;层控构造裂缝主要发育在白云石条带、砂质/白云质混合条带和顺层方解石脉等脆性层;层理缝主要为异常高压成因,发育集中在阜二段中下部Ⅲ~Ⅴ亚段。层理缝与顺层方解石脉、白云石条带和砂质/白云质混合条带中发育的层控构造溶蚀缝洞既是页岩油的有利储集空间,也是高效渗流通道,有利于页岩油富集;穿层构造裂缝有效性较好,相对于页岩的基质更为富集页岩油(S 1),但其纵横向连通性较好,因而也是页岩油逸散的高效通道,对阜二段Ⅴ亚段“Ⅴ下”甜点层保存条件不利,对Ⅳ亚段甜点层影响较小,平面上与断层距离越小,断层规模越大,构造裂缝越发育且越不利于页岩油保存。

2022年东台地震序列区域速度结构和精确定位

2022年江苏东台接连发生数十次小地震,其中,震级最大的M_(S)3.0地震导致震中附近震感明显。为探究该地区近期地震相对活跃的原因,文中收集了2008—2022年的地震走时资料,利用双差层析成像方法对苏北盆地的速度结构和地震位置进行了联合反演,获得了震中区P波三维速度结构和地震精确定位结果,并结合断裂分布、震源机制解和当地工业活动等资料,对地震序列可能的发震机制和发震构造进行了探讨。结果显示:1)重定位后,地震序列总体呈近SN向带状展布,发震优势深度在11~16km,与已探明的断裂带缺乏明显联系。结合震源机制结果推测,序列下方可能存在NNE-SSW向隐伏构造。2)震中区下方速度分布具有明显的非均匀性特征,15km深度处存在纺锤状P波高速异常体,地震序列的震源位置表现出从该异常体向远处扩散的发震特点。3)震中区附近现存多处工业活动,其中五烈—时堰—溱东作业点、地震序列和深部高速异常三者的位置存在一定的关联性,且作业时间和发震时间相近。由此推断,此次地震序列的发生与深部非均匀速度结构有关,震中附近的工业活动可能改变了区域应力状态,导致了能量的释放。