准噶尔盆地吉木萨尔凹陷芦草沟组页岩油“甜点体”储集特征及成因机理

Reservoir characteristics and genesis of shale oil "sweet spots" in Lucaogou Formation, Jimsar Sag, Junggar Basin

王然 常秋生 钱永新 刘国良 万敏 黄立良

WANG Ran CHANG Qiusheng QIAN Yongxin LIU Guoliang WAN Min HUANG Liliang

中国石油 新疆油田分公司 勘探开发研究院, 新疆 克拉玛依 834000

Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay, Xinjiang 834000, China

准噶尔盆地吉木萨尔凹陷芦草沟组页岩油层系岩性复杂，非均质性强，“甜点体”形成规律是制约地质理论研究和勘探开发的一个关键难题。通过岩心观察、薄片鉴定和含油性分析，针对“甜点体”地质特征进行了表征，分析了影响产能的地质因素，确定了可动油孔隙的形成机理。吉木萨尔凹陷芦草沟组“甜点体”的岩性主要为岩屑长石粉细砂岩、云屑砂岩和砂屑云岩，孔隙度为5.75%~11.9%，渗透率为（0.02~1.26）×10-3 μm2，其中岩屑长石粉细砂岩的孔喉贡献率最大，“甜点体”的储集空间为溶蚀粒间（内）孔、裂缝；页岩油产能的大小受控于可动油孔隙的分布以及岩石组分中泥质、石英质和白云质的含量，可动油孔隙是在同生—准同生淋滤作用和酸性流体埋藏溶蚀联合作用下形成的，层理缝沟通溶孔是控制渗透率大小的关键因素。储层成岩过程中储集空间耦合生排烃作用最终形成“甜点体”，其形成的沉积环境为受波浪作用较强的云坪、混合坪、滨湖滩砂和碳酸盐岩浅滩沉积。该发现可对同成因类型页岩油的勘探和开发提供指导。

The shale oil layers of the Lucaogou Formation in the Jimsar Sag of Junggar Basin have complex lithology and strong heterogeneity. The formation of "sweet spots" is a key problem restricting exploration and development. Through core observation, thin section analysis and oil-bearing capacity analysis, the geological features of the "sweet spots" were characterized, the geological factors affecting productivity were analyzed, and the formation mechanism of movable oil pores was determined. The lithology of "sweet spots" of the Lucaogou Formation in the Jimsar Sag is mainly lithic feldspar fine sandstone, dolomitic sandstone and gypsum dolomite, with a porosity of 5.75%-11.9% and a permeability of (0.02-1.26)×10-3 μm2, of which the lithic feldspar fine sandstone made the largest contribution to pore throats. Intergranular (intragranular) pores and fractures provide storage space for "sweet spots". Shale oil yield is controlled by the pore distribution for movable oil and the contents of argillaceous, quartz and dolomite. The movable oil pores are formed under the combined action of syngenetic and quasi-syngenetic leaching and acid fluid burial dissolution. The key factor to control permeability is the connection of dissolved pores by bedding cracks. In the process of reservoir diagenesis, the coupling of hydrocarbon generation and expulsion in the reservoir space will eventually form a "sweet spot", mainly in environments such as dolomitic flat, mixed flat, lakeside beach sand and carbonate shoal which are strongly influenced by waves. This discovery can provide guidance for the exploration and development of shale oil of the same genetic type.

国家油气重大专项 2016ZX05046-006;中国石油天然气集团有限公司科技重大专项 2017E-0402;中国石油天然气集团有限公司科技重大专项 2019E-26

https://doi.org/10.11781/sysydz202004604