Identification of sweet spots in shale-type and siltstone-type“shale oil systems”:A case study of the Chang 7 Member in Ordos Basin  

作　　者：Songqi PAN Qiulei GUO Caineng ZOU Zhenhua JING Ming YUAN Ying HE He ZHENG Ying MU Zhi YANG Shixiang LI Xinping ZHOU Songtao WU Hanlin LIU Feng YANG Yuanjia HAN 

机构地区：[1]Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China [2]State Key Laboratory of Enhanced Oil Recovery,Beijing 100083,China [3]School of Earth Resources,China University of Geosciences,Wuhan 430074,China [4]Institute of Porous Flow and Fluid,University of Chinese Academy of Sciences,Beijing 100049,China [5]Changqing Oilfield Company,PetroChina,Xi’an 710018,China

出　　处：《Science China Earth Sciences》2023年第7期1647-1663,共17页中国科学（地球科学英文版）

基　　金：funded by the National Natural Science Foundation of China(Grant Nos.41902151,42172180,41830431,and 41902144);the Petro China Scientific Research and Technology Development Project(Grant No.2021DJ1802)。

摘　　要：Mid-high maturity shale oil is the most realistic field for the scale breakthrough of terrestrial shale oil production in China.Generally,three deficiencies hinder shale oil development in China:heavy oil density,small sweet spot areas,and poor distribution continuity.Thus,identifying the“sweet spots”in shale oil reservoirs is critical for the efficient exploration and development of terrestrial shale oil.This study targets the siltstone type(Class-Ⅱshale oil)and pure shale type(Class-Ⅲshale oil)of the Chang 7 Member in the Ordos Basin,and identifies three stratigraphic units,namely the hydrocarbon accumulation unit,hydrocarbon generation unit,and hydrocarbon retention unit,which together constitute the in-source“shale oil system”.The hydrocarbon accumulation unit is mainly siltstone,where the hydrocarbons are migrated from shales.It has favorable porethroat network connectivity with a pore connectivity ratio of 32–57%,being the siltstone-type sweet spots.The hydrocarbon generation unit is mainly composed of high-TOC mudstone/shale and is the main contributor to in-source hydrocarbon generation and expulsion.This unit has high three-dimensional connectivity(28–30%),as shown by the pore-throat network model,associated with vertical paths for hydrocarbon expulsion.The hydrocarbon retention unit is mainly composed of low-TOC mudstone/shale retaining self-generated and migrated hydrocarbons.The pore connectivity rate is 17–42%,and the pore-throat network connectivity direction is uneven.Light and low-carbon-number hydrocarbons are preferentially trapped or even sealed in small pores of the retention unit,forming the typical mudstone/shale-type sweet spots.In the process called shale oil intrasource migration,the oil migrates in source rocks causing component fractionation,which allows more shale oil to enrich in the hydrocarbon accumulation and retention units to form sweet spots,compared with the hydrocarbon generation unit.The migration paths include the one from mudstone/shale to siltstone interl

关 键 词：Shale oil system Hydrocarbon accumulation unit Hydrocarbon generation unit Hydrocarbon retention unit Differentiated enrichment Sweet spots window Pore-throat network Throat direction 

分 类 号：P618.13[天文地球—矿床学] TE321[天文地球—地质学]