含气页岩不同纹层及组合储集层特征差异性及其成因——以四川盆地下志留统龙马溪组一段典型井为例  

Reservoir characteristics and genetic mechanisms of gas-bearing shales with different laminae and laminae combinations:A case study of Member 1 of the Lower Silurian Longmaxi shale in Sichuan Basin,SW China

作　　者：施振生[1,2] 董大忠 王红岩[1,2] 孙莎莎 武瑾[1,2] SHI Zhensheng;DONG Dazhong;WANG Hongyan;SUN Shasha;WU Jin(PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;National Energy Shale Gas R&D(Experiment)Center,Langfang 065007,China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]国家能源页岩气研发(实验)中心,河北廊坊065007

出　　处：《石油勘探与开发》2020年第4期829-840,共12页Petroleum Exploration and Development

基　　金：国家科技重大专项“大型油气田及煤层气开发”(2017ZX05035-001);国家自然科学基金“晚三叠世四川盆地不同类型三角洲内部构型及成因模式”(41572079)。

摘　　要：基于薄片、氩离子抛光大片成像和纳米CT扫描等实验分析资料,对四川盆地下志留统龙马溪组一段典型井含气页岩不同纹层及组合储集层特征差异性及其成因进行研究。结果表明,该套页岩发育泥纹层和粉砂纹层,二者的单层厚度、物质组成、孔隙类型及结构、面孔率和孔径分布均存在差异性。泥纹层单层厚约100μm,有机质含量大于15%,石英含量大于70%,有机孔占比和面孔率高,顺层缝发育,有机质和有机孔均相互连通构成网状。粉砂纹层单层厚约50μm,有机质含量为5%~15%,碳酸盐含量大于50%,无机孔占比高,顺层缝不发育,有机质和孔隙均相互不连通。泥纹层和粉砂纹层的形成可能与富硅生物的勃发有关,间歇期形成泥纹层,勃发期形成粉砂纹层。泥纹层和粉砂纹层可构成条带状粉砂、砂泥递变和砂泥薄互层3类纹层组合。条带状粉砂纹层组合的孔隙度和水平与垂直渗透率比值均最大,砂泥递变纹层组合次之,砂泥薄互层纹层组合最低,泥纹层与粉砂纹层含量比值造成水平与垂直渗透率比值差异。Based on thin-section,argon-ion polished large-area imaging and nano-CT scanning data,the reservoir characteristics and genetic mechanisms of the Lower Silurian Longmaxi shale layers with different laminae and laminae combinations in the Sichuan Basin were examined.It is found that the shale has two kinds of laminae,muddy lamina and silty lamina,which are different in single lamina thickness,composition,pore type and texture,plane porosity and pore size distribution.The muddy laminae are about 100μm thick each,over 15%in organic matter content,over 70%in quartz content,and higher in organic pore ratio and plane porosity.They have abundant bedding fractures and organic matter and organic pores connecting with each other to form a network.In contrast,the silty laminae are about 50μm thick each,5%to 15%in organic matter content,over 50%in carbonate content,higher in inorganic pore ratio,undeveloped in bedding fracture,and have organic matter and organic pores disconnected from each other.The formation of mud lamina and silt lamina may be related to the flourish of silicon-rich organisms.The mud lamina is formed during the intermittent period,and silt lamina is formed during the bloom period of silicon-rich organisms.The mud laminae and silt laminae can combine into three types of assemblages:strip-shaped silt,gradating sand-mud and sand-mud thin interlayers.The strip-shaped silt assemblage has the highest porosity and horizontal/vertical permeability ratio,followed by the gradating sand-mud assemblage and sand-mud thin interlayer assemblage.The difference in the content ratio of the mud laminae to silt laminae results in the difference in the horizontal/vertical permeability ratio.

关 键 词：含气页岩 纹层 储集层特征 成因机制 下志留统 龙马溪组 四川盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]