威荣深层页岩气储层微观孔隙结构表征及分类评价

doi:10.13809/j.cnki.cn32-1825/te.2021.02.003

摘要/Abstract

摘要：

为研究深层页岩储层评价标准,对其储层微观孔隙结构进行了研究。基于“高精度、跨尺度”微观孔隙结构研究思路,利用氮气吸附、高压压汞、扫描电镜以及矿物分析电镜等实验,形成一套全孔径范围的储层微观孔隙结构定量表征技术,建立了深层页岩气储层评价标准。研究结果表明：①孔隙类型为有机孔、粒间孔、粒内孔、微裂缝4类,不同类型孔隙差异大,以有机孔占主导,其面孔占比大于50 %,孔隙形态复杂,呈椭圆形、不规则状或扁平状分布,形状系数为0.50~0.90,分形维数（D）为2.72~2.92;②基于全孔径表征技术及分形理论将孔隙结构分为4类,其中Ⅰ类孔隙结构的有机孔发育（有机孔占比大于等于50 %）,分选较好（分选系数大于等于0.7）,变异系数较大（变异系数大于等于1.1）,孔隙半径分布呈多模态分布;③综合孔隙结构分类及储层参数,将页岩储层分为4类,其中Ⅰ类储层的关键参数为总有机碳含量（TOC）大于等于4 %,总含气量大于等于6 m³/t,孔隙度大于等于6 %,脆性矿物含量大于等于50 %,杨氏模量大于等于36 GPa,泊松比小于等于0.225,为Ⅰ类孔隙结构,该类储层主要分布于2—3¹小层,为水平井最优靶窗位置。

关键词: 威荣深层页岩气, 五峰组—龙马溪组, 微观孔隙结构表征, 分形理论, 评价标准

Abstract:

In order to study the evaluation standard of deep shale reservoirs, their micro pore characteristics have been studied. Based on the ideas of micro pore structure research with “high precision and cross scale”, and by using nitrogen adsorption, high pressure mercury injection, scanning electron microscope and mineral analysis electron microscope experiments, a series of quantitative characterization techniques of reservoir micro pore structure with full pore size range are formed, and the evaluation standard of deep shale gas reservoir is established. The research results show that: ①The pore types include organic pore, intergranular pore, intragranular pore and microfracture, which are of great difference with each other. The organic pores are dominant with the surface porosity more than 50 %, the pore morphology is complex with the distribution of elliptic, irregular or flat, the shape coefficient is 0.50~0.90, and the fractal dimension（D） is 2.72~2.92. ②Based on the full pore size characterization technology and fractal theory, the pore structure can be divided into four types. The organic pores of type Ⅰ pore structure are developed （organic pore ratio Is greater than or equal to 50 %）, well sorted （sorting coefficient Is greater than or equal to 0.7）, large coefficient of variation （variation coefficient Is greater than or equal to 1.1）, and multi-modal distribution of pore size. ③According to the classification of pore structure and reservoir parameters, shale reservoirs are divided into four types. The key parameters make up the structure of type Ⅰ are TOC≥4 %, total gas content Is greater than or equal to 6 m³/t, porosity Is greater than or equal to 6 %, brittle mineral content Is greater than or equal to 50 %, Young’s modulus Is greater than or equal to 36 GPa, Poisson’s ratio Is less than or equal to 0.225, and type Ⅰ pore structure. This kind of reservoir is mainly distributed in 2—3¹ layers, which is the optimal target window position.

Key words: Weirong Deep Shale Gas Field, Wufeng-Longmaxi Formation, micro pore structure characterization, fractal theory, evaluation criterion

中图分类号:

TE122

熊亮,庞河清,赵勇等. 威荣深层页岩气储层微观孔隙结构表征及分类评价[J]. 油气藏评价与开发, 2021, 11(2): 154-163.

Liang XIONG,Heqing PANG,Yong ZHAO, et al. Micro pore structure characterization and classification evaluation of reservoirs in Weirong Deep Shale Gas Field[J]. Reservoir Evaluation and Development, 2021, 11(2): 154-163.

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孔隙类型	赋存环境	扫描电镜典型照片	AmicSCAN矿物分析电镜典型照片	孔隙半径（μm）	形状系数	伸长率（%）	分形维数	有机孔占比（%）	面孔占比（%）
有机孔	有机质中	A5井,3 570.7 m	A5井,3 570.7 m	0.01~0.20	0.50~0.90	≤5	2.72~2.92	≥50	55~65
粒间孔	黏土矿物间	A5井,3 570.7 m	A5井,3 570.7 m	>0.10	0.60~0.70	>5	2.30~2.90	40~50	25~30
粒内孔	方解石、石英、长石中	A5井,3 570.7 m	A5井,3 570.7 m	0.01~0.70	0.70~0.87	<3	2.22~2.45	40~50	10~15
微裂缝	硅质纹层、碳酸盐岩纹层中发育	A5井,3 570.7 m	A5井,3 570.7 m

孔隙结构类型	主要分布小层及岩性	有机孔占比（%）	孔隙半径（μm）	孔隙度（%）	TOC （%）
单峰型	2小层,钙质-黏土质-硅质混合型页岩	≥50	0.01~0.20	4.1~6.9	≥4
双峰型	3³、4小层, 硅质-钙质- 黏土质页岩	40~50	0.05~10.00	5.1~6.4	2~3
单斜型	3¹小层,生物硅质页岩	≥50	0.05~0.20	5.1~7.4	≥4
单斜型	⑤—⑨号层, 黏土质页岩	<25	<0.05	4.2~5.0	<2

孔隙结构分类	TOC（%）	有机孔占比（%）	渗透率（mD）	储能评价参数（10^-4mD）	中值半径（nm）	分选系数	变异系数	孔隙类型	孔隙半径分布形态
Ⅰ类	≥4	≥50	≥0.120	≥85	≤41.5	≥0.7	≥1.1	有机孔发育,无机孔相对发育, 孔隙连通性好,微裂缝发育	多模态宽广型
Ⅱ类	3~4	40~50	0.040~0.120	15~85	41.5~43.0	0.6~0.7	0.9~1.1	有机孔相对发育,见部分无机孔、微裂缝	双模态宽广型
Ⅲ类	2~3	25~40	0.015~0.040	5~15	43.0~44.5	0.5~0.6	0.7~0.9	有机孔较发育,无机孔相对发育, 存在一定量微裂缝	双模态高低不对称型
Ⅳ类	<2	<25	<0.015	<5	>44.5	<0.5	<0.7	无机孔较发育,少量有机孔	单模态集中型

储层类别	地质参数				工程参数
储层类别	TOC （%）	孔隙度（%）	总含气量（m³/t）	孔隙结构类型	脆性矿物含量（%）	黏土矿物含量（%）	杨氏模量（GPa）	泊松比	层理及微裂缝
Ⅰ类	≥4	≥6	≥6	Ⅰ类	≥50	≤35	≥36	≤0.225	极发育
Ⅱ类	3~4	5~6	4~6	Ⅱ类	42~50	35~45	32~36	0.225~0.250	发育
Ⅲ类	2~3	3~5	2~4	Ⅲ类	35~42	45~55	28~32	0.250~0.280	较发育
Ⅳ类	<2	<3	<2	Ⅳ类	<35	>55	<28	>0.280	一般