Identification and Evaluation of Organic-Rich Shale in Kuqa Depression, Tarim Basin, Western China

Abstract

Tarim Basin has great potential of gas resources in China, which is also rich in continental shale gas. Based on geological analysis of single well, and combining outcrop, drilling, logging and seismic data, this paper analyzes sedimentary environment, burial depth and distribution of dark shale in the Mesozoic of the Kuqa Depression, especially geochemistry, reservoir bed characteristics and gas content through experimental testing, and evaluates shale gas potential of the key formations in the Jurassic by using the volumetric method and the volume method. Six sets of organic-rich dark shale developed in the Mesozoic of the Kuqa Basin, and the Kezilenur Formation in the Jurassic has the most favorable geological conditions. (1) This formation was developed in swamp facies and semi-deep lake and deep lake facies, with burial depth 317~3980 m (average 2776 m), organic-rich shale (TOC>4%) thickness of 24~113 m, distribution area of 1702 km²; (2) TOC is 0.48%~9.66% (average 4.10%), main organic matter type is III, maturity 0.54%~1.83% (average 1.19%); (3) Lithology is mainly dark mudstone and carbonaceous mudstone. The average content of quartz, feldspar, carbonate and other brittle mineral is 44.4%. Clay mineral is mainly illite and illite-smectite, with hard and brittle texture. Reservoir space is mainly organic matter holes, micro-pores between clay minerals, inter-crystalline pores and a large number of fractures with porosity 0.33%~3.44% (average 1.35%), permeability 0.43~1.9 μD (average 1.1 μD); (4) Maximum adsorption capacity is 1.19~7.55 m³/t (average 3.812 m³/t), showing positive correlation with organic carbon content (TOC). The Kezilenur Formation has evaluated resources reaching 3.05×1012 m³, as a favorable area for shale gas exploration and development.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015