Paleokarst fracture-vug types and their reconstruction in buried hill area, Tahe oilfield, Tarim Basin

The Tahe oilfield in the Tarim Basin contains typical karsr fractured-vuggy reservoirs with caverns and solution fractures and vugs as the major storage space. The classification and description of the paleokarst fracture-vug poses a challenge for the fine development of the oil reservoirs. This study takes the Block 4 in the Tahe area as an example to investigate the genetic correlation, controlling factors of distribution and productivity differences of these karst fracture-vug. Three types of karst fracture-vug, i.e., epikarst type, underground river type and fault-controlled type, are then proposed based on whether they share unified karst water flow pattern and circulation path. Meanwhile, three processes that have modified the fracture-vug are recognized, i.e., the architectural transformation, cave collapse and in-filling. The intrinsic architecture and spatial distribution of the fracture-vug are also characterized. Guided by the understandings, a producing reserve assessment and production-injection well pattern readjustment have been successfully carried out in the Block 4, verifying the guiding significance of the study. © 2022, OIL & GAS GEOLOGY Editorial Board. All right reserved.