Characterization of a Lacustrine Shale Reservoir and the Evolution of its Nanopores: A Case Study of the Upper Cretaceous Qingshankou Formation in the Songliao Basin,Northeastern China

The Songliao Basin is one of the most important petroliferous basins in northern China. With a recent gradual decline in conventional oil production in the basin, the exploration and development of unconventional resources are becoming increasingly urgent. The Qingshankou Formation consists of typical Upper Cretaceous continental strata, and represents a promising and practical replacement resource for shale oil in the Songliao Basin. Previous studies have shown that low-mature to mature Qingshankou shale mainly preserves type Ⅰ and type Ⅱ1 organic matter, with relatively high total organic carbon(TOC) content. It is estimated that there is a great potential to explore for shale oil resources in the Qingshankou Formation in this basin. However, not enough systematic research has been conducted on pore characteristics and their main controlling factors in this lacustrine shale reservoir. In this study, 19 Qingshankou shales from two wells drilled in the study area were tested and analyzed for mineral composition, pore distribution and feature evolution using Xray diffraction(XRD), scanning electron microscopy(SEM), low-pressure nitrogen gas adsorption(N2-GA), and thermal simulation experiments. The XRD results show that clay, quartz, and feldspar are the dominant mineral constituents of Qingshankou shale. The clay minerals are mostly illite/smectite mixed layers with a mean content of 83.5%, followed by illite, chlorite, and kaolinite. There are abundant deposits of clay-rich shale in the Qingshankou Formation in the study area, within which many mineral and organic matter pores were observed using SEM. Mineral pores contribute the most to shale porosity;specifically, clay mineral pores and carbonate pores comprise most of the mineral pores in the shale. Among the three types of organic matter pores, type B is more dominant the other two. Pores with diameters greater than 10 nm supply the main pore volume;most are half-open slits and wedge-shaped pores. The total pore volume had no obvious linear relationship with TOC content, but had some degree of positive correlation with the content of quartz + feldspar and clay minerals respectively. However, it was negatively correlated with carbonate mineral content. The specific surface area of the pores is negatively related to TOC content, average pore diameter, and carbonate mineral content. Moreover, it had a somewhat positive correlation with clay mineral content and no clear linear relationship with the content of quartz + feldspar. With increases in maturity, there was also an increase in the number of carbonate mineral dissolution pores and organic matter pores, average pore diameter, and pore volume, whereas there was a decrease in specific surface area of the pores. Generally, the Qingshankou shale is at a low-mature to mature stage with a TOC content of more than 1.0%, and could be as thick as 250 m in the study area. Pores with diameters of more than 10 nm are well-developed in the shale. This research illustrates that there are favorable conditions for shale oil occurrence and enrichment in the Qingshankou shale in the study area.     

松辽盆地白垩系砂岩储集层特征

白垩系砂岩储层是松辽盆地主要的油气层，砂岩成分以石英，长石和岩屑为主，为长石砂岩，岩屑长石砂岩和长石质岩屑砂岩，储层孔隙包括粒间孔，粒内溶孔，铸模孔，胶结物内溶孔，裂缝等，储层孔隙演化经历了早、中、晚等成岩阶段，在中成岩阶段,晚成岩阶段早期和晚期有3次次生孔隙发育，其对储层性质有明显的改善。本区砂岩储集层可分为4个类型，且具有不同的分布规律。     

含粉砂质层页岩储层孔隙结构和物性特征:以张家滩陆相页岩为例

鄂尔多斯盆地东南部延长组张家滩页岩储层中发育有大量粉砂质层,全面系统地理清张家滩页岩孔隙结构和物性特征,需要对比研究粉砂质纹层发育页岩、粉砂质层不发育的泥质页岩以及粉砂岩。本文选取了22块页岩样品,通过压汞法、气体吸附法和气测孔渗法等多种测试手段,结合扫描电镜观察,在对组成3种岩石类型的粉砂质层和泥质层孔隙发育类型研究的基础上,分析了3种岩石类型孔隙结构和物性特征的差异,并讨论了造成上述差异的影响因素。结果表明,粉砂质纹层发育页岩和粉砂岩孔径在100 nm以上的中-大孔孔体积较大,具有更好的储集和渗流能力。通过对比粉砂质层和泥质层的组分、沉积结构和成岩作用等的差异可知：粉砂质层中石英、长石等粉砂级刚性碎屑颗粒的富集有利于原始孔隙的形成和在物理压实过程中的保存;有机酸存在造成的酸性成岩环境有利于长石等颗粒发育溶蚀孔隙;液态烃等在颗粒表面形成的薄膜能够有效地抑制石英等胶结作用的发生。与泥质层相比,粉砂质层具有更好的孔隙形成和保存条件,使得粉砂质纹层发育页岩和粉砂岩的孔隙结构和物性特征明显优于泥质页岩。     

Deep Continental Scientific Drilling Engineering Project in Songliao Basin: progress in Earth Science research

The Songke No.2 well (eastern hole) (referred to as Well SK-2), one of the “two wells and four holes” of the Deep Continental Scientific Drilling Engineering Project in the Songliao Basin, is in Anda City, Heilongjiang Province, and was officially completed on May 26, 2018. The scientific goals of Well SK-2 cover four aspects: paleoclimate research, resource and energy exploration, primary geological research, and development of deep earth exploration techniques. Since the official commencement of drilling in 2014, the Well SK-2 scientific drilling engineering team has organized and implemented drilling for coring, in situ logging, chemical analysis of core elements, and deep structural exploration around the well. Currently, the following preliminary scientific research progress has been made: 4334.81 m in situ core data has been obtained; the centimeter-level high-resolution characterization of the most complete and continuous Cretaceous continental strata ever unearthed has been completed, and the standard profile of continental strata has been initially established; the unconventional natural gas resources and basin-type hot dry rocks in the deep Songliao Basin were found to have good prospects for exploration and development; the climatic evolutionary history of the Cretaceous continental strata was rebuilt for the first time, covering hundreds of thousands to millions of years, and the major events of Cretaceous climate fluctuations have been discovered; all these reveal strong evidence for the subduction and aggregation of paleo-ocean plates, providing a theoretical basis for the re-recognition of the genesis of the Songliao Basin and for deep earth oil and gas exploration. The implementation of the Deep Continental Scientific Drilling Engineering Project in the Songliao Basin is of great significance for exploring the mysteries of the Earth and solving major problems such as those related to the deep energy environment. It is a solid step along the road of “going deep into the Earth”.     

陆相页岩气储层孔隙发育特征及其主控因素分析:以鄂尔多斯盆地长7段为例

鄂尔多斯盆地延长组是目前最具页岩气潜力的研究层段之一。本文以该盆地东部长7段为研究对象,运用氮气吸附法及氩离子剖光扫描电镜分析对页岩气储层孔隙结构及孔隙类型进行分析和测定,并结合岩石矿物组分、有机质成熟度以及总有机碳（TOC）质量分数,讨论了孔隙结构和影响因素。结果表明,长7段页岩气储层孔隙结构复杂,根据吸附回线形态可分为2类：Ⅰ类回线主要对应孔径为2.6~4.2 nm的狭缝结构或楔形结构的平行板状孔或微裂缝,具体可分为黏土矿物矿片间孔隙、有机质内狭缝状孔隙及基质微裂隙等类型;Ⅱ类回线主要为分布于2.3~3.1、3.5~3.8、4.3~5.2 nm等多个孔径段的开放型圆筒状孔,包括有机质孔和残余粒间孔。中孔和微孔是总孔体积和比表面积的主要贡献者。w（TOC）是延长组页岩总孔体积及比表面积的主要控制因素,与总孔体积及比表面积均呈正相关关系;镜质体反射率及矿物含量对孔隙发育的控制作用不明显,但黏土矿物对微孔孔容贡献较大,其中伊利石质量分数与BET比表面积及孔容有较好的相关性。     

松辽盆地升平地区深层成岩作用数值模拟与次生孔隙带预测

为了预测松辽盆地深部碎屑岩成岩阶段和次生孔隙发育带的展布、研究储层孔隙发育史与其他成藏要素的匹配关系，本文将传统的成岩作用研究和数值模拟技术相结合，在作用模型和效应模型的基础上，建立了一个成岩作用数值模拟的综合模型。松辽盆地升平地区深层登娄库组成岩演化的研究表明，在泉头期末，登娄库组进入晚成岩阶段A1期，烃源岩进入生油门限，储层开始发育次生孔隙；在青山口期末，登娄库组处于晚成岩阶段A—B期，登二段烃源岩进入大量生、排烃的成熟阶段，生烃时间、储层次生孔隙发育时间和圈闭形成时间匹配良好，油气藏开始形成。目前，本区的登娄库组在南部主要处于晚成岩阶段C期，在北部处于晚成岩阶段B期。成岩指数ID=0．85～1.15，且有砂体发育的地区，即为本区次生孔隙发育带的分布范围。     

Pore Characteristics and Factors Controlling Lacustrine Shales from the Upper Cretaceous Qingshankou Formation of the Songliao Basin,Northeast China: A Study Combining SEM,Low-temperature Gas Adsorption and MICP Experiments

To investigate pore characteristics and the factors controlling lacustrine shales,geochemical,mineralogical and petrophysical experiments were performed on 23 shale samples from the Qingshankou Formation of the Songliao Basin,China.A comparison of mercury injection capillary pressure (MICP) and low-temperature N2 adsorption pore-size distribution showed that MICP has a higher pore-size distribution (PSD) line in its overlapping pore diameter range,which may be elevated by the higher pressure of MICP.Therefore,in the overlapping range,low-temperature N2 adsorption data were preferred in pore characterization.Negative correlations were observed between pore volumes and TOC content,indicating organic matter pores are not well-developed in the studied samples.This may be related to their low grade of maturity and type I kerogens.There existed negative relationships between pore volumes and S1,which illustrated that liquid hydrocarbons occupied some pore space.Micropore volume had a better correlation with S1 than mesopore and macropore volumes,which suggests that liquid hydrocarbons preferentially occur in micropores.No obvious relationships between pore volumes and quartz or feldspar were observed,while pore volumes increased with the increasing clay mineral content.These relationships indicate that intraparticle pores in clay minerals represent the principal pore type.     

松辽盆地东南隆起超大型油页岩矿床特征及成因

研究区内已发现的超大型油页岩矿床位于吉黑地槽褶皱系松辽中断陷的一个三级构造单元--松辽盆地东南隆起内。研究区主要发育白垩纪地层,属于陆源碎屑岩沉积。经钻井岩心观察和采用“费舍尔”方法对含油率测试分析表明,油页岩层主要赋存在早白垩世青山口组和晚白垩世嫩江组。含油页岩层系整体为一套厚层的暗色泥页岩和油页岩组合。井间油页岩层对比和油页岩平面展布特征显示,该区油页岩呈层状、规模大、分布范围广、矿层稳定、连续性好。研究证实矿石含油率与有机质组分及总有机碳关系密切,矿石灰分大,属低品质油页岩矿石。通过对油页岩特征及成矿环境分析,认为矿床成因属于腐泥型页岩-油页岩。     

压汞法测定页岩孔隙特征的影响因素分析

压汞法是目前测定岩石内部孔隙特征的常用方法,但测试结果受样品尺寸、测量范围等多种因素的影响。本文以页岩为主要研究对象,采用压汞法等测试手段分析了不同的样品尺寸、接触角等条件下的孔隙特征。结果表明:1孔隙率与所选的孔径范围有关,在7.1 nm~100μm孔径范围内测量孔隙率的准确性更高;样品制备时可能产生人为裂隙导致孔隙率的测量误差较大。2在一定孔径范围内,与人工合成样品相比,页岩的平均孔径、孔隙率、比孔容等特征值受样品尺寸影响更大。页岩样品尺寸的减小,不仅能增加小孔隙间的连通性,而且可以降低较大裂隙的影响。3接触角从130°增加到150°,平均孔径变大约35%。因此应在准确测量接触角的情况下采用小尺寸样品进行测试,同时进一步完善并统一压汞法测量页岩孔隙特征的实验规范,以提高测试结果的准确性和可比性。     

松辽盆地北部油页岩资源潜力评价

为评价松辽盆地北部油页岩资源潜力,开展了14口地质井的钻探、2 100多口老井的复查和多项油页岩的样品分析测试工作。根据油页岩分析测试资料,结合录井、测井、地震、沉积等研究成果,总结了油页岩主要特征,并用体积丰度法初步估算了埋深小于1 km的油页岩和页岩油潜在资源量。结果表明:松辽盆地北部油页岩主要发育在青山口组一段和嫩江组一、二段沉积时期的湖相沉积中,是盆地两次最大湖泛期的产物;嫩江组和青山口组油页岩平均岩石密度分别为2.20和2.18 t/m³,平均含油率分别为5.55%和5.39%;油页岩有机质类型为Ⅰ型和Ⅱ₁型,处于未成熟低成熟阶段,有机质丰度极高,是最好的生油岩。松辽盆地北部油页岩分布广泛、层位稳定、资源潜力巨大,初步估算埋深小于1 km的油页岩潜在资源量为6 008.40×10⁸ t,页岩油潜在资源量为297.50×10⁸ t。油页岩可以成为未来大庆油田常规油气的重要补充或接替资源。     

松辽盆地北部中浅层油页岩分布特征及资源潜力

利用有机碳含量、镜质体反射率等手段,对松辽盆地北部上白垩统青山口组一段、嫩江组一段、嫩江组二段三个层位油页岩的分布、地球化学特征及富集条件进行研究表明:目标层主要以深湖相、半深湖相的黑色泥岩和页岩为主,厚10~30m不等;有机质丰度较高,TOC值介于1.873%~10.625%之间,平均6.47%,干酪跟类型以Ⅰ型、ⅡA型为主,成熟度Ro普遍为0.41~0.78,处于低成熟阶段;三个层位油页岩有机质来源以湖生生物及海侵带来的藻类等母源物质为主,沉积时期主体处于海侵深水、强缺氧环境,有机质保存条件较好。     

松辽盆地深层地层及构造特征

本文研究了松辽盆地深层地层层序、划分方法及其区域构造特征、演化规律,指出沙河子组、营城组在火山活动间歇期发育有湖泊沼泽相煤系地层,这对找煤工作具有重要的指导意义。     

松辽盆地梨树断陷页岩气资源潜力评价

松辽盆地梨树断陷纵向上发育白垩系沙河子组和营城组两套主力泥页岩烃源岩层系,其沉积环境有利、厚度大、分布广。沙河子组以Ⅱ段页岩气地质条件最好,其w(TOC)分布范围为0.11%~8.20%(平均值1.45%);营城组发育两段优质泥页岩,Ⅰ段w(TOC)为0.26%~12.01%(平均值1.96%),Ⅱ段w(TOC)为0.06%~5.03%(平均值1.06%)。有机质类型以Ⅱ₁-Ⅲ型为主,含少量I型。沙河子组R_o普遍较高,断陷西部基本进入过成熟阶段,缓坡带处于成熟-高成熟阶段。营城组R_o变化范围较大,小城子、孤家子和十屋地区R_o达到2.00%以上。两套泥页岩脆性矿物体积分数为32.10%~62.90%,具有较好的储集性能。断陷内有多口探井在沙河子组和营城组的厚层泥页岩段钻遇高气测显示。营城组I段泥页岩含气量为0.62~3.09 m³/t。采用概率法初步预测出沙河子组和营城组页岩气资源量为6 645.34× 10⁸ m³。秦家屯地区和苏家屯次洼为页岩气勘探的有利目标区,桑树台深洼带为较有利目标区。     

松辽盆地长岭断陷沙河子组页岩有机显微组分孔隙演化规律研究

有机质孔隙是页岩储集空间的重要组成部分,具有强烈的非均质性,阻碍对页岩储层质量的正确认识和评价,其本质是受有机显微组分类型及其在生烃过程中孔隙演化的影响。本文采用场发射扫描电镜和荧光显微镜定位观察手段实现特定显微组分孔隙发育特征的表征,结合Image J图像处理技术,对不同演化阶段的显微组分进行定量化统计,总结不同有机显微组分的孔隙演化规律。研究结果表明:固体沥青孔隙度随着成熟度的升高呈现先增加后减小的趋势,在固体沥青反射率SBR_O介于1.6%～2.0%时,固体沥青孔隙最为发育,而以SBR_O=2.0%为界,固体沥青孔隙度开始减小。镜质体和惰质体的孔隙发育规律相似,随着成熟度增加,总体表现出先减小而后微弱增加的趋势。在生油窗阶段,镜质体和惰质体孔隙度最小,无机矿物和固体沥青的充填使胞腔孔隙损失达90%以上,而进入高成熟阶段,固体沥青孔隙的发育使原始胞腔孔隙得到一定程度的恢复,成为镜质体和惰质体残余孔隙的主要贡献者,贡献率达56.73%和100%,可见固体沥青孔隙对页岩储层储集空间的重要性。综合沉积成岩作用和生烃作用,页岩储层在未成熟阶段和高成熟阶段晚期孔隙最为发育,前者有机质以原始胞腔孔隙为主,后者以固体量孔隙为主。明确有机显微组分孔隙演化规律为页岩有利储层预测和页岩气生产开发储层改造提供参考。     

松辽盆地北部青一段油页岩地球化学特征及其记录的古湖泊学信息

油页岩地球化学特征及其记录的古湖泊学信息是揭示油页岩成矿富集规律的关键佐证。根据含油率、TOC、岩石热解、元素分析、生物标志化合物检测及有机显微组分分析,精细刻画了松辽盆地北部ZY1井青一段油页岩的地球化学特征,并分析了其记录的古湖泊学信息,探讨了古湖泊对油页岩有机质富集的控制作用。结果表明：青一段发育8层中等偏好品质的油页岩,下部为高品质油页岩富集层段;油页岩的含油率和TOC质量分数相关性极好,处于未熟—低成熟度演化阶段,生烃潜力大;油页岩中含丰富的萜类和甾类化合物,有机质类型主要为Ⅰ型,有机质来源主要为层状藻占优势的湖泊水生生物。地球化学参数指示,青一段下部古湖泊生产力呈现3个低→高的旋回,对应的古湖泊水体盐度呈现为3个半咸水-咸水旋回、古湖泊水体氧化还原性表现为还原-强还原-还原的厌氧环境,其中旋回Ⅱ后期湖泊生产力最高,对应的水体盐度最高、还原性最强。表明湖泊富营养化造成的高湖泊生产力是青一段高品质油页岩有机质富集的物质基础,盐度分层控制下强还原的湖底环境是高品质油页岩有机质富集的良好保存条件。     

沁水盆地武乡区块上古生界煤系页岩气储层孔隙特征和孔隙结构

储层孔隙特征和孔隙结构是影响页岩气赋存与储集的重要因素。为评价海陆过渡相高演化煤系页岩储层性质与页岩气储集性能,应用扫描电子显微镜、高压压汞、低温N₂和 CO₂气体吸附、微米CT扫描、核磁共振实验方法,对沁水盆地武乡区块上古生界煤系页岩气储层孔隙微观特征和孔隙结构进行了研究。结果表明,沁水盆地武乡区块上古生界煤系页岩样品中发育多种类型微观孔隙,常见粒间孔、粒内孔和微裂缝,有机质孔几乎不发育;武乡区块煤系页岩气储层样品孔隙总孔容分布在0.021 9~0.073 5 mL/g之间,平均值为0.039 9 mL/g,总比表面积主要分布在11.94~46.83 m²/g之间,平均为29.16 m²/g,其中介孔(2~50 nm)和微孔(<2 nm)是煤系页岩气储集的主要载体。煤系页岩中的高配位数孔隙数量越多,相应的孔容和孔比表面积越大,孔隙连通性越好;在孔隙数量和总孔容相差不大的前提下,山西组煤系页岩储层孔隙结构与连通性比太原组煤系页岩稍好。     

陆相裂谷盆地构造沉积学特征:以松辽盆地伏龙泉断陷为例

构造沉积学不仅强调大地构造背景条件对盆地演化的控制作用,同时还注重盆地内部的构造特征与沉积充填特征之间的控制及响应关系研究。陆相裂谷盆地发育过程中,构造作用强烈,盆地沉积充填过程复杂,进行构造沉积学研究对揭示盆地构造沉积演化过程具有重要意义。以大量地震、钻测井资料为基础,结合大地构造背景资料,研究松辽盆地伏龙泉断陷发育过程中的构造、沉积演化特征,分析构造活动与沉积作用之间的响应及控制关系,并由此讨论半地堑陆相湖盆的沉积充填演化规律及其控制因素。研究表明,在伏龙泉断陷盆地演化过程中,早期的火山岩隆起对盆地初始裂陷期形态具有明显的影响作用;边界断层的分布及其生长速率特征则对盆地结构演化过程起着首要的控制作用。盆地裂陷期,研究区古气候环境比较稳定,构造因素是控制该陆相裂谷盆地地层序列与沉积特征的首要因素;断裂发育特征决定了盆地的古地貌特征,而盆地的古地貌特征直接影响着盆地内部的沉积充填类型与沉积体系展布格局;区域构造抬升与断块掀斜是该半地堑盆地内部发育不整合面的主要因素。在陆相裂陷盆地的构造沉积特征研究中,构造沉积学显示出了其必要性与适用性,有利于在揭示构造沉积现象的同时,合理解释其地质成因。     

黔西地区下石炭统旧司组页岩气聚集条件及含气性分析

为研究旧司组页岩气聚集条件和含气性特征,以黔西地区下石炭统旧司组页岩为研究对象,采用薄片鉴定、X-射线衍射分析、覆压孔渗、扫描电镜、低温氮吸附、有机地球化学、含气量现场解析、等温吸附等测试方法开展研究。结果表明:黔西地区旧司组富有机质页岩广泛发育,厚度主体上介于30~100 m之间,有机碳含量高,有机质类型主要为Ⅱ型,处于过成熟生干气阶段;矿物成分主要为石英和黏土矿物,脆性指数均大于50%,为超低孔、超低渗,孔隙类型多样,孔径介于2~4 nm之间,以中孔为主,比表面积和总孔体积较大,具备良好的页岩气聚集条件;页岩微观孔隙的分形维数(D₁、D₂)较大,平均值分别为2.804 1、2.753 8,页岩孔隙结构较为复杂、非均质性较强;现场解析总含气量主体介于1.5~3.0 m³/t之间,等温吸附气量介于1.58~4.52 m³/t之间,含气性能较好,旧司组显示出具有良好的页岩气勘探潜力。     

鄂尔多斯盆地延长探区延长组页岩气储层孔隙结构特征

为了评价陆相页岩气储层的储集空间和储气能力,以鄂尔多斯盆地延长探区上三叠统延长组长7段、长9段页岩为研究对象,运用电子扫描显微镜、高压压汞、低温CO2和N2气体吸附等实验方法,对陆相页岩气储层孔隙类型特征、孔隙结构及其影响因素进行研究。结果表明：(1)延长探区上三叠统延长组陆相页岩发育多种类型微观孔隙,以粒间孔和粒内孔为主,少量晶间孔和溶蚀孔,有机质孔发育较少,为陆相页岩气赋存提供了储集空间;(2)延长组页岩中介孔(2～50 nm)贡献了其主要的孔容和比表面积,占总孔容的7437%,占总比表面积的6440%,且长9段页岩的总孔容和总比表面积均大于长7段页岩;(3)延长组页岩孔隙结构以狭缝型孔和板状孔为主,孔径主要分布在04～09 nm、3～25 nm和5～200 μm区间段内,延长组页岩平均孔径为853 nm,且长7段页岩平均孔径大于长9段页岩;(4)页岩有机碳含量、有机质成熟度及矿物成分含量共同影响着延长组页岩孔隙的发育,其中矿物成分含量是以介孔孔隙为主的延长组页岩孔隙发育的主控因素,有机碳含量及成熟度的增加主要对页岩中微孔孔隙的发育起到积极作用。