Formation mechanical mechanism of low-angle fractures in pre-salt carbonate reservoirs: a case study from Carboniferous KT-I formation of the NT oilfield in the eastern margin of the Precaspian Basin, Kazakhstan

• DOI: 10.1007/s13202-024-01783-x
• Publication Date: 2024-04-12T07:03:21Z
• Authors: Changhai Li; Lun Zhao; Bo Liu; Weiqiang Li; Kaibo Shi; Wenqi Zhao; Jianxin Li; Qiang Zhu; Yunhai Li; Caiqin Ma
• Keywords: Magnetic dip; Offshore geotechnical engineering

Abstract Fracture is an important factor that affects the oil and gas productivity of carbonate reservoirs. Much researches have been done on origin high-angle fractures in reservoirs, but few efforts made genetic mechanical mechanism low-angle fractures. Based seismic data, core conventional logging data rock mechanics experimental combined with three-dimensional situ stress field simulation methods, features, formation geological conditions (LAFs) were analyzed by applying Coulomb–Moore criterion, Griffith criterion non-coordination criterion. The proportion number shear as high 90.2%, while tensile only 9.8% study area. Shear are mainly unfilled fractures, partially filled LAFs formed second tectonic movement, which knee-fold structure west low east developed buried depth most parts KT-I 800 m when area develops structure, a maximum 1800 minimum 70 m, dip angle steepest part stratum about 20°. A large under joint influence tectonics abnormally pressure water, including near-horizontal non-weak fabrics section (type I fractures), having certain bedding II fractures) weak III fractures). type follows Type strata angle, strata. comprehensive pre-existing strong horizontal extrusion, Low-angle caused reverse faults area, following Griffith’s research this paper not reveals pre-salt reservoirs also provides guidance for prediction solving problem water channeling fields.