基于埋深变化的川南龙马溪组页岩孔隙特征及控制因素分析

[研究目的]中国浅层-中深层页岩气勘探开发技术已经趋于成熟,深层页岩成为下一步勘探开发的重点,探明不同埋深条件下页岩的孔隙特征及其控制因素利于推动深层页岩的评优选区工作.[研究方法]本文基于核磁共振、场发射扫描电镜和X-射线衍射等实验分析手段,对比性评价了川南地区不同深度的龙马溪组页岩孔隙度、孔隙结构参数特征并进行影响...     

枣园油田孔一,二段储层成岩作用和孔隙结构特征

本文综合应用研究区目的层段岩芯样品的各项分析测试资料,对储集砂岩的成岩作用和孔隙结构进行研究,揭示了枣园油田储集砂岩的成分成熟度和结构成熟度均较低;各组分含量变化大是造成储层成岩变化和孔隙结构复杂的因素之一。孔一、二段砂岩经历了压实、胶结、交代、溶解和自生矿物充填等成岩作用。孔一段上部孔隙类型以原生孔隙为主,孔隙和喉道发育、孔渗高,但孔喉分选差;下部原生和次生孔隙并存。孔二段主要是次生孔隙,孔喉细、分选差,孔渗性较孔一段上部差。     

鄂尔多斯盆地镇泾区块延长组长81储层成岩作用特征及其对储集物性的影响

鄂尔多斯盆地镇泾区块上三叠统延长组长81储层具有成分成熟度低,结构成熟度中等到好的特点,岩性以岩屑长石砂岩和长石岩屑砂岩为主.长81砂岩属于特低孔特低渗储层,以次生溶蚀粒间孔为主要储集空间.目前储层正处于中成岩阶段A期,主要发育压实、胶结、溶解和交代4种成岩作用类型.机械压实作用是造成长81储层埋深小于2000 m砂岩...     

黄骅坳陷三马地区中深层储层孔隙发育及主控因素分析

本文根据储集岩样品的显微特征，分析了黄骅坳陷三马地区下第三系中一深部储层中孔隙的成因类型、微观特征及演化规律。研究表明，研究区储层孔隙演化具有明显的阶段性，可划分为原生孔隙、混合孔隙及次生孔隙3个发育带。中一深部储层中原生孔隙所占比例很小，以次生孔隙为主，随埋藏增大，次生孔隙所占比例相应增加。中深部储层中主要分布3个次生孔隙发育带，其深度分别为3200～3500m，3600～4000m，4200～4500m。次生孔隙类型主要为粒间溶孔和粒内溶孔，也可见到铸模孔和微裂缝。导致原始孔隙降低的主要原因为压实和胶结作用，次生孔隙形成机理主要包括长石、方解石的溶解作用和矿物的转化等。本文还讨论了储层岩相、岩性特征、地层水中有机酸浓度的改变、早期方解石的充填、烃类注入、异常高压及微裂缝等地质与地球化学因素对中深部储层成岩作用和次生孔隙形成与分布的控制作用。     

四川盆地蜀南地区上三叠统须家河组低孔低渗储层特征及形成机理

蜀南地区须家河组为一套辫状河三角洲平原分支河道沉积的岩屑砂岩、长石岩屑质石英砂岩和岩屑质石英砂岩。埋藏深度变化较大（0～2 673 m）,大部分埋深800～2 000 m,平均孔隙度4.64%,平均渗透率0.147×10-3μm2,属于低孔低渗储层。造成低孔低渗的主要原因是:（1）在构造背景上,须家河组沉积时研究区靠近刚由海变陆而隆升的物源区,沉积物搬运距离较短,分异程度低,大量的泥岩、千枚岩等塑性岩屑及杂基被保存下来,同时碎屑颗粒分选磨圆程度较差,均不利于原生孔隙的形成;（2）在沉积条件上,由于辫状河河道水动力不稳定,侧向改道迅速,早期泥岩易被冲蚀,导致砂泥混杂,砂岩中含较多杂基,堵塞充填原始孔隙;（3）早期持续快速的埋藏过程,压实作用强烈,岩屑压实变形被挤入粒间孔隙中,同时普遍发育的石英次生加大使得砂岩越发致密,孔隙消失殆尽。（4）研究区须家河组远离沉积中心,缺乏烃源岩成熟产生的酸性流体溶蚀改造,导致次生孔隙不发育。     

白音查干凹陷桑合地区腾格尔组储层特征及主控因素分析

白音查干凹陷桑合地区腾格尔组碎屑岩储层岩性主要为长石砂岩、岩屑长石砂岩和长石岩屑砂岩,填隙物以钙质胶结物为主,孔隙式胶结。储集空间类型主要为原生孔隙,以点状、片状喉道为主,具有喉道半径差别大,分选差,孔隙连通性差等孔隙结构特征。沉积环境及成岩作用为该区储层发育的主控因素。扇三角洲平原和前缘过渡带为有利储层发育区。压实及胶结作用通过减小孔隙空间及填充喉道对储层起破坏性作用;溶蚀作用则通过形成次生溶孔对储层起建设性作用。纵向上,发育两个储层物性异常带;平面上,扇三角洲平原与前缘相的过渡带为近物源、多物源、快速堆积模式,压实作用占主导地位,沉积相带与成岩相带共同作用形成平衡带。多种控制因素的综合效应,是该平衡带储层物性变好的主要原因。     

吐哈盆地巴喀气田八道湾组致密砂岩储层分析及孔隙度演化定量模拟

在吐哈盆地巴喀气田八道湾组砂岩储层特征及控制因素分析的基础上,以地史时间和埋藏深度为变量,以现今孔隙度为约束条件,紧密结合埋藏阶段分析和关键成岩阶段窗口分析,分阶段建立了巴喀气田八道湾组储层从埋藏初始直至现今的孔隙度演化定量模型,动态体现了整个孔隙度演化过程。定量模拟结果表明：研究区储层总孔隙度演化是一个七段式分段函数,各个阶段孔隙度演化或遵循减小模型或遵循减小与增大的叠加模型;机械压实阶段的孔隙度减小模型是以埋深为自变量的函数,压实和胶结综合作用阶段则是以埋深和埋藏时间为变量的函数;孔隙增大模型适用于Ro值范围为0.6～1.0的溶蚀作用窗口内;早期的纯机械压实作用使八道湾组储层已接近致密,溶蚀作用之前的压实和胶结综合作用导致储层致密化,而后期溶蚀作用仅在一定程度上提高了孔隙空间。     

Modelling of porosity evolution and mechanical compaction of calcareous sediments

A continuum mechanics model for the gravitational compaction of sediments is derived by assuming that the sediments are normally pressured and in a one-dimensional state of stress. Sediment strength is characterized in terms of effective stress laws adopted from soil mechanics. The model is a relatively simple mathematical formula that gives the porosity as a function of burial depth. The shape of the porosity profile is controlled by two mechanical parameters, the compression index and the void ratio at an effective stress of 100 kPa. The model was verified by analysing the porosity—depth data of oozes and chalk from the Ontong Java Plateau, gathered during Leg 130 of the Ocean Drilling Program. The mechanical parameters of the sediments were estimated using a least-squares method to fit the theoretical profile to the porosity data. The theoretical profile described accurately the ooze porosity data over depth ranges of 100 m or more. However, over smaller length-scales of 10–50 m there were systematic deviations between the theoretical porosity values and the ooze porosity data. The porosity deviations correlated with variations in the mean grain size of the sediments, due in part to changes in the foraminifera abundance. In the case of the oozes, the estimated mechanical parameters were consistent with published values obtained from one-dimensional compression tests. In contrast, the estimated mechanical properties for the chalks differed from published values. The chalk porosities were lower than could be explained by mechanical compaction. This explanation is supported by the compressional (P-wave) velocity data. In the chalk sections, the P-wave velocity increases more rapidly with burial depth than it does in the ooze sections, suggesting that sediment elastic properties are increasing due to interparticle binding.     

准噶尔盆地克-百逆掩断裂带上下盘储层差异性及其形成机理

基于岩芯、薄片和物性数据等资料,从构造演化、沉积体系时空展布、成岩作用特征及储层质量角度,对准噶尔盆地西北缘克拉玛依-百口泉地区逆掩断裂带上、下盘二叠系-侏罗系储层特征进行系统对比研究,探讨储层差异性形成机理.在断裂上盘,沉积物粒度较粗,通常为冲积扇或辫状河沉积砾岩、砂质砾岩,埋藏较浅,孔隙性较好.在断裂下盘,沉积物相对较细,通常为辫状河三角洲或扇三角洲前缘沉积砂岩,埋藏较深且孔隙性整体较差;局部层段发育沸石和长石的强烈溶蚀.通过分析认为,研究区储层埋藏史(断裂演化史)控制上、下盘储层砂体成因,决定储层现今埋深及成岩演化,影响储层次生孔隙的形成;沉积体系发育受同生的克-百主断裂控制,影响储层粒度、岩石成分成熟度、结构成熟度,决定储层原始孔隙结构发育情况.     

埋藏(机械)压实-侧向挤压地质过程下深层储层孔隙演化与预测模型

早期长期浅埋、后期快速深埋以及晚期强烈的侧向挤压作用是西部前陆盆地共性地质演化过程,受此地质演化过程影响,明确深层储层孔隙、孔径、喉径等参数的演化特征并进行定量评价,对油气勘探具有重要意义。开展成岩物理模拟实验,并与实际地质分析相结合,定量评价与预测了库车坳陷克拉苏构造带白垩系深层储层的孔隙类型与演化特征。研究结果认为,研究区深层储层的孔隙类型、含量变化及演化规律可划分为4个阶段,其中第3个演化阶段即深层储层快速埋藏后的早期阶段是孔隙度和渗透率提高的重要阶段,是此类地质过程下深层有利储层形成的关键时期。构造侧向挤压与成岩压碎破裂造缝、次生溶蚀两种改造机制,改善了深层储层的储集性、提高了渗透性,进而建立了深层储层孔隙预测模型。定量揭示出库车坳陷克拉苏构造带在埋深7 000~8 000 m甚至更深层段,储层孔径、喉径增大并保持,仍发育有效储层。     

压实过程中埋深和时间对碎屑岩孔隙度演化的共同影响

在相同埋深条件下,由于经历时间不同,地层压实程度将会存在差别。从粘弹塑性体应力-应变模型（Bingham 模型）推导出均速埋藏条件下地层孔隙度是埋深和经历时间的双元函数。该函数充分表明,在压实作用阶段,埋藏时间和埋深两个因素对地层孔隙度演化的影响都是非常重要的。为了充分证实这一结论,作者首先分析3个代表性沉积盆地地层孔隙度与埋深和埋藏时间的关系,阐明了除了埋深因素的作用,埋藏时间明显影响到了地层孔隙度的改变。另外,利用沉积物实验室压实物理模拟实验结果与实际盆地地层压实特征的差异性,进一步证明了压实过程中承压时间对压实程度起着重要的作用。任一深度地层孔隙度与埋深的表面关系不能掩盖地层孔隙度受埋藏过程控制的实质,即地层孔隙度受埋藏时间和深度的双重影响。     

成岩作用对储层孔隙的影响--以辽河盆地荣37块气田下第三系为例

通过对岩芯、铸体薄片、阴极发光薄片观察及X－衍射分析,认为辽河盆地下第三系砂岩储层成岩作用中的压实作用和胶结作用减小和破坏储层孔隙,溶蚀作用则增加储层孔隙,且后者仅在一定深度范围内作用,并从沉积相、砂岩的成因及岩屑成份等方面探讨了成岩作用对储层孔隙度的影响。     

克拉苏冲断带白垩系储层成岩作用及其对储层质量的影响

利用大量岩石薄片、铸体薄片、测录井资料及岩芯观察等资料,对库车坳陷克拉苏冲断带白垩系巴什基奇克组储集层的岩石组分、成岩作用及孔隙类型特征等进行了系统研究。其岩石学特征为:成分成熟度低,分选中-好,磨圆次棱角状-次圆状,结构成熟度中等-偏低。储集空间为次生孔隙及原生孔隙。储层经历了压实、胶结、溶解、破裂等成岩作用,主要处于中成岩A2-B期。压实作用以机械压实为主,胶结作用主要为碳酸盐胶结;溶蚀作用导致碳酸盐胶结物、长石颗粒和少量岩屑溶解、破裂作用产生裂缝。在克拉苏断裂的上、下盘地层中,压实作用及胶结作用是孔隙减少的主要原因。断裂带上盘埋深较浅,抬升遭受表生溶蚀作用使得溶蚀孔隙非常发育;断裂带下盘埋深较深,压实和胶结作用使得储层致密化,后期构造挤压破裂作用形成的裂缝及溶蚀扩大缝有效地改善了深部储层物性。     

鄂尔多斯盆地代家坪地区长6致密油储层孔隙结构特征及分类评价

利用取心井铸体薄片、扫描电镜、X衍射、压汞测试等分析化验资料,在系统研究鄂尔多斯盆地代家坪地区长6致密油储层微观孔隙结构特征、成因机理的基础上对其进行分类评价。结果表明长6储层储集空间以粒内溶孔、残余粒间孔为主,次为粒间溶孔、岩屑溶孔,喉道类型以片状、弯片状和缩颈型喉道为主。沉积作用形成的岩石组构和成分差异决定了储层原始孔渗条件,并影响到后期成岩作用的类型和强度;各成岩事件对物性影响定量计算表明,强烈的压实和碳酸盐胶结是造成储层原生孔隙结构被破坏的主要原因;构造挤压则加剧了孔隙结构的非均质性;结合盆地埋藏史将孔隙演化分为浅埋藏胶结减孔带、中埋藏压实减孔带、深埋藏溶蚀增孔带和深埋藏胶结减孔带等4个阶段。通过微观孔喉结构参数与储层宏观物性相关性分析,优选最大连通喉道半径、主要流动喉道半径、分选系数、排驱压力和中值压力等5个孔隙结构参数作为分类依据;进一步采用Q型聚类分析将长6储层分为4种类型,结果表明Ⅰ、Ⅱ类储层孔隙结构较好,为研究区有利开发目标区。     

四川盆地马路背地区上三叠统须家河组致密砂岩储层成因分析

马路背构造位于四川盆地东北部,该地区须家河组发育致密砂岩储层,却形成了“高产、稳产”的规模气藏。论文充分利用各种岩矿分析化验资料,从岩石学特征、成岩作用、孔隙演化等方面深入探讨了马路背地区须二段（T₃x2）致密砂岩储层的成因。结果表明:马路背地区须家河组以大巴山变质岩为母岩沉积了一套三角洲前缘中粒岩屑砂岩和石英砂岩;无论是石英砂岩还是岩屑砂岩,无论埋深大小,铸体薄片下孔隙均不发育,扫描电镜偶见微孔,物性很差;强烈的埋藏压实作用造成各种孔隙的缩小与消失;早燕山期（199~100 Ma）、中晚燕山期（100~65 Ma）、喜山期（65 Ma以来）等多期构造强挤压进一步造成孔隙减小和消失,构造压实减孔量大约4%;埋藏压实与构造强压实减孔的同时,产生了不同规模断层和裂缝（颗粒裂纹—粒间微裂缝—层间断层）,沟通微孔,形成断层—裂缝—微孔隙组成的断缝储集体。这类储集体主要受构造应力大小控制,构造挤压最强的部位,裂缝最发育;其次受岩性和砂岩厚度控制,中—薄层石英砂岩中最发育。     

四川盆地五峰组—龙马溪组重点井含气页岩孔隙类型与孔径分布

针对四川盆地五峰组-龙马溪组过成熟海相页岩,开展普通薄片观察、SEM成像、X-衍射全岩组分和黏土矿物分析、TOC含量测定、N2-CO2联合吸附实验和RG测定.结果表明,海相页岩发育有机孔、无机孔和微裂缝.有机孔多呈气孔状或海绵孔状,大、小混杂;无机孔多呈三角状、棱角状或长方形状;微裂缝多呈条带状,能有效沟通有机孔和无机...     

Research advances,geological implication and application in Ordos Basin of the “pore-size controlled precipitation” in diagenesis of carbonate rock reservoir

Based on the discovery of pore-size controlled mineral precipitation and cementation heterogeneity in carbonate rock reservoirs,the state of art and the geological implications are summarized,referring to the fluid-rock interaction and chemical hydrodynamics in porous media. (1)The pore-size controlled precipitation phenomenon is common in geological environments,as shown by the heterogeneous cementation and eventual features that the large pores are filled while small pores can be preserved. Related studies are mainly divided into three aspects,including pore structure observations at different scales,numerical simulation of fluid-rock interaction and mineral precipitation experiment. (2)The kinetic models related to surface chemistry can be used to explain the heterogeneous precipitation affected by pore-size distribution. The larger interfacial tension and mineral crystal curvature in the micropores result in the much higher effective solubility.Thus the fluids in micropores can maintain a higher supersaturation with no minerals precipitation. (3)The pore-size controlled precipitation leads to the selective preservation of micropores. It means that the much larger pores tend to be cement-filled while the smaller pores are preserved in the case of coexistence of pores at different scales. The impacts of cementation types on the overall permeability of rock are different. The pore-size controlled precipitation phenomenon is also worthy of attention in the research of geothermal development and geologic sequestration of carbon dioxide. In the last part, based on the heterogeneous cementation and porosity distribution of the Majiagou Formation in the Ordos Basin,we study the impacts of diagenetic fluids properties,origin and cementation patterns on the evolution of pore structure and high-quality reservoir distribution.The discovery and emphasis of pore-size controlled precipitation is of great theoretical significance to our understanding of the complex fluid-rock interaction process,which provides a new perspective for reservoir diagenesis and pore preservation.     

Burial-dominated cementation in non-tropical carbonates of the Oligocene Te Kuiti Group, New Zealand

Cementation of bryozoan-echinoid-benthic foraminiferal temperate shelf carbonates of the Oligocene Te Kuiti Group, North Island, New Zealand, occurred mainly during subsurface burial. The calcite cements in the limestones are dominated by equant and syntaxial rim spar which typically becomes ferroan (given an iron supply) and, compared to the skeletal material with normal marine δ¹⁸O values from +2 to −1‰, more depleted in ¹⁸O with depth of burial, the δ¹⁸O composition of bulk cement samples ranging from −1 to −7‰. These trends reflect the establishment in pore waters during sediment burial of reducing conditions and gradually increasing temperatures (20–50°C), respectively. The δ¹³C values (0 to +3‰) of the cements remain the same as the host marine shells, suggesting the source of carbon in the cements was simply redistributed marine carbonate derived from shell dissolution.

Two gradational burial diagenetic environments influenced by marine-derived porewaters are arbitrarily distinguished: shallow burial phase and moderate burial phase. During the shallow burial phase, down to 500–600 m sub-bottom depth, the carbonates lost at least 25% of their original porosity by mechanical compaction and were selectively cemented by non-ferroan or usually ferroan, variably luminescent, slightly ¹⁸O-depleted sparry calcite cement (δ¹⁸O −2 to −4‰), mainly as syntaxial rims about echinoid grains. These shallow-burial cements form less than about 10% of total cement in the majority of the limestones and their source was probably mainly mild intergranular dissolution of calcitic skeletal fragments accompanying the onset of chemical compaction. During the moderate burial phase, between about 600 and 1100 m sub-bottom depth, porosity loss continued (typically to about 70% of its original value) as a result of pressure-solution of calcitic bioclasts associated with more advanced stages of chemical compaction. This involved development of a wide variety of non-sutured and microstylolitic solution seams, including both single and composite, wispy or continuous, bedding-parallel types and non-parallel reticulate forms. The released carbonate was precipitated as ferroan (or non-ferroan where iron supply was negligible), dull luminescent, strongly ¹⁸O-depleted (δ¹⁸O −4 to −7‰), mainly equant calcite spar cement, occluding available pore space in the limestones.     

影响碎屑岩天然气储层物性的主要控制因素

碎屑岩天然气储层，尤其是埋藏历史较长、埋深较大的致密碎屑岩天然气储层物性的控制因素比较复杂，本文通过对我国中新生代主要含气盆地的碎屑岩储气层埋藏历史和成岩阶段与孔隙度关系的研究，提出了按产状将碎屑岩储层孔隙分为粒间孔、粒间溶孔、组分内孔隙和裂隙四种类型的划分方案，分析了各类孔隙对砂岩孔渗性的贡献。从碎屑颗粒物理性质和化学性质；砂岩中泥质杂基和自生粘土矿物；沉积速度与埋藏历史；碎屑岩粒径和分选程度；泥质岩成岩作用；构造背景和构造运动以及镜质体反射率和有机质成熟度等方面讨论了它们对碎屑岩天然气储层物性的控制机理。     

Pore Characteristics of the Fine‐Grained Tight Reservoirs in the Yabulai Basin,Northwestern China

This work investigated the pore structure characteristics and reservoir features of the finegrained tight reservoirs in the lower member of the Xinhe Formation(J_2 x_1) in the Xiaohu subsag,Yabulai Basin based on core samples through various techniques. Interbedded silt/fine sandstones and mudstones are developed in the study area. Scanning electron microscopy(SEM) images were used to delineate different types of pores, including primary intergranular pores, secondary intergranular and intragranular pores, organic pores and fractures. The pore types were distinguished by pore size, pore area, location and formation process. The pore radii of the fine-grained rocks range from 1 nm to 1.55μm, mainly concentrated between 5 and 300 nm by low pressure N_2 adsorption and MICP analyses. The pore structure parameters of pore throat size and pore throat sorting coefficient are both positively correlated with porosity, while pore throat sorting coefficient has a negative correlation with permeability. The pore structures of the studied samples are much related to the mineral type and content and grain size, followed by TOC content. In these rocks with relatively low TOC and low maturity, the rigid minerals protect pores with pressure shadow from collapse, and dissolution-related pores contribute a lot to inorganic porosity. In contrast, these rocks with abundant TOC contain a large number of organic pores. The permeability of the fine-grained tight reservoir is mainly dominated by larger pore throats, while a large number of small pores(mostly 0.1 μm) contribute considerably to porosity. These results have deepened our understanding of the interbedded fine-grained tight reservoirs and can be applicable to fine-grained reservoirs in a similar setting.