Efectiveness and petroleum geological signifcance of tectonic fractures in the ultra‑deep zone of the Kuqa foreland thrust belt:a case study of the Cretaceous Bashijiqike Formation in the Keshen gas feld  

作　　者：Rong-Hu Zhang Ke Wang Qing-Lu Zeng Chao-Feng Yu Jun-Peng Wang 

机构地区：[1]PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100086,China [2]PetroChina Hangzhou Research Institute of Geology,Hangzhou 310023,Zhejiang,China

出　　处：《Petroleum Science》2021年第3期728-741,共14页石油科学（英文版）

基　　金：This work was supported by the National Key Research and Development Project(No.2019YFC0605501);the National Science and Technology Major Project(2016ZX05003001).

摘　　要：The buried depth of the gas-producing reservoir in the Kuqa foreland thrust belt of the Tarim Basin exceeds 6000 m.The average matrix porosity of the reservoir is 5.5%,and the average matrix permeability is 0.128×10^(−3)μm^(2).In order to reveal the characteristics and efectiveness of ultra-deep fractures and their efects on reservoir properties and natural gas production,outcrops,cores,thin section,image logs and production testing data are used to investigate the efectiveness of tectonic fractures in ultra-deep reservoirs in the Kuqa foreland thrust zone,and the corresponding geological signifcance for oil and gas exploration and development are discussed.Tectonic fractures in the thrust belt include EW-trending high-angle tensile fractures and NS-trending vertical shear fractures.The former has a relatively high flling rate,while the latter is mostly unflled.Micro-fractures are usually grain-piercing-through cracks with width of 10-100 microns.In the planar view,the efective fractures are concentrated in the high part and wing zones of the long axis of the anticline,and along the vertical direction,they are mainly found in the tensile fracture zone above the neutral plane.The adjustment fracture zone has the strongest vertical extension abilities and high efectiveness,followed by the nearly EW longitudinal tensile fracture zone,and the netted fracture zone with multiple dip angles.The efectiveness of fracture is mainly controlled by fracture aperture and flling degrees.Efective fractures can increase reservoir permeability by 1-2 orders of magnitude.The higher part of the anticline is associated with high tectonic fracture permeability,which control enrichment and high production of natural gas.The netted vertical open fractures efectively communicate with pores and throats of the reservoir matrix,which forms an apparent-homogenous to medium-heterogeneous body that is seen with high production of natural gas sustained for a long term.

关 键 词：Fracture efectiveness Ultra-deep Reservoir Foreland thrust belt Kuqa depression Geological signifcance 

分 类 号：P618.13[天文地球—矿床学]