Uncover the Mystery of Lacustrine Shale Oil Reservoir by Integrating Advanced Logging Technologies and Special Core Measurements – Case Study of Chang 7-3 Shale Oil Reservoir, Erdos Basin, China

Abstract

Chang 7-3 lacustrine shale oil reservoir in Ordos basin is characterized by complex lithology and high heterogeneity with various mineral compositions (quartz, carbonates, feldspars, pyrites and volcanic ash), total organic carbon and pore structure. How to delineate the shale oil reservoir, how to identify the ‘sweet spots’ and its distribution are the two major challenges and objectives for this study. Advanced logging technologies were used to identify the different shale oil reservoir facies, and special core measurements (Tight Reservoir Analysis, Thin Section scanning , Mercury Injection Capillary Pressure, N2 and CO2 Gas sorption test, XRD and Nuclear Magnetic Resonance analysis) were designed to describe the reservoir from a micro point of view. The advanced core analysis results and logging technologies were integrated to depict the characters of the shale oil reservoir from microscopic to macroscopic scale, and the quality of the reservir was clarified, ‘the sweet pot’ were been targeted. Reservoir characteristics such as mineral composition, reservoir physical properties, reservoir pore space types, pore size distribution, oil content, kerogen type and maturity of organic matter, organic carbon content and distribution were revealed by this method and six shale oil reservoir facies were classfied, inculding super high gamma ray siliceous shale, high gamma ray siliceous shale, high gamma ray argillaceous shale, high gamma ray tuffaceous shale, medium gamma ray siliceous shale and medium gamma ray argillaceous shale. High gamma ray siliceous shale and medium gamma ray siliceous shale are proved to be the best shale oil reserovir for this formation, with 2~8% of TOC, 2~12% of effective porosity, more than 50% of quartz content, high propotion of macropores. This type of shale oil reservoir lies mainly in the south of Tianhuan depression and may related to the volcanic activity in this area. The conclusion of this pioneered project has been used to optimize the field E&P strategy in the basin for the best shale oil sweet spot selection. The wells tested based on the recommendation from this study got promising production after fracturing as well.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018