Title: Development characteristics and prediction of fractures in deep-ultradeep tight sandstone reservoirs of Kuqa Depression: a case study of the Bashijiqike and Baxigai formations in Dabei 9 Block

Authors: Peiming Huang; Wei Ju; Aslaug Clemmensen Glad; Yu Zhong; Haoran Xu; Yan Liang

Addresses: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, China University of Mining and Technology, Xuzhou, 221008, China; School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, 221116, China ' Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, China University of Mining and Technology, Xuzhou, 221008, China; School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, 221116, China ' The Danish Offshore Technology Centre, Technical University of Denmark, Elektrovej 375, 2800, Kgs. Lyngby, Denmark ' School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, 221116, China ' The Second Exploration Team of Shandong Provincial Bureau of Coal Geology, Jining, 272100, China ' School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, 221116, China

Abstract: Deep-ultradeep tight sandstone gas reservoirs are extremely important promising future energy. Natural fractures can improve the permeability and impact the overall reservoir quality. With the Dabei 9 Block of Kuqa Depression as an example, this study investigated and predicted the development and distribution of natural fractures in the tight sandstone reservoir based on R/S analysis method. Tensile-shear fractures are dominant fracture type within the block. Natural fractures primarily strike NW-SE and NE-SW directions with relatively high dip angle. Nearly 50% fractures are unfilled and partly filled. The coefficient index of fracture development Q was defined and calculated according to the lg(R/S) function. Error analysis of fracture prediction was also carried out. The results show that the Q corresponds to fracture density, and higher Q value commonly indicates larger density. Errors between fracture predictions and measures can be caused by various factors including fracture occurrence, fracture filling, limitation of conventional logging range, and multiple interpretations of logging curves. This study is expected to provide geological references for tight sandstone gas exploration and development in the Dabei 9 Block of Kuqa Depression. [Received: September 5, 2022; Accepted: August 19, 2023]

Keywords: fracture development characteristics; fracture prediction; R/S analysis method; ultra-deep tight sandstone; Dabei 9 Block; Kuqa Depression.

DOI: 10.1504/IJOGCT.2024.137857

International Journal of Oil, Gas and Coal Technology, 2024 Vol.35 No.3, pp.279 - 298

Received: 04 Sep 2022
Accepted: 19 Aug 2023
Published online: 05 Apr 2024 *

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