Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (5): 1259-1274.doi: 10.11743/ogg20240505

• Petroleum Geology • Previous Articles     Next Articles

Deformation characteristics and hydrocarbon accumulation models of the Lan’ga and Hotan River fault zones in the Tarim Basin

Hailong MA1,2,3(), Lin JIANG1,2, Wenlong DING3,4,5(), Pengyuan HAN3, Zhen WANG1,2, Changjian ZHANG1,2, Huan WEN1,2, Liming DING1,2, Jie LI1,2   

  1. 1.Northwest Oil Field Company,SINOPEC,Urumqi,Xinjiang 830001,China
    2.Key Laboratory for Enhanced Oil Recovery for Fractured-Vuggy Reservoirs,SINOPEC,Urumqi,Xinjiang 830001,China
    3.School of Energy Resources,China University of Geosciences (Beijing),Beijing 100083,China
    4.Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism (Ministry of Education),China University of Geosciences (Beijing),Beijing 100083,China
    5.Key Laboratory of Shale Gas Resource Strategic Evaluation (Ministry of Land and Resources),China University of Geosciences (Beijing),Beijing 100083,China
  • Received:2024-04-06 Revised:2024-09-05 Online:2024-10-30 Published:2024-11-06
  • Contact: Wenlong DING E-mail:297048455@qq.com;dingwenlong2006@126.com

Abstract:

A Y-shaped thrust-detachment fault striking NNE-near NS directions is developed in the middle of the Tarim Basin, composed of strike-slip for a half and thrust for another half. The fault exhibits significantly different structural style from those in adjacent areas and involve varying fault systems on both sides. However, its formation mechanisms and structural evolution remain unclear. In this study, we investigate the formation mechanisms and evolutionary characteristics with the structural analysis of the Hotan River and Lan’ga fault zones. Comparing the two fault zones in terms of the hydrocarbon accumulation characteristics in the Tahe oilfield, we delve into the characteristics of hydrocarbon migration and accumulation along the Hotan River fault zone. The results indicate that the Lan’ga and Hotan River fault zones are formed during the Late Caledonian, featuring a semi-strike-slip, semi-reverse-thrust Y-shaped thrust-detachment structure. These fault zones converge downwards into strike-slip faults and thrust upwards into the Silurian strata, forming faulted anticlines. Regional in-situ stress is identified as the main cause of the formation of both fault zones. At the end of the Early Ordovician, large-scale NNE- and NNW-trending strike-slip faults were formed in the Tabei Uplift and NNE-trending strike-slip faults were formed in the Bachu Uplift due to stresses from the southwest, southeast, and north. During the Late Caledonian, thrust-detachment faults that converged downward into strike-slip faults and thrust upward to the Silurian strata were formed due to the compression from Eastern Kunlun Orogen and the South Tianshan Ocean, cutting through the strike-slip faults. Thus, those strike-slip faults in their hanging walls got reactivated. Consequently, their hanging walls exhibit more developed fracture networks and a higher degree of fracturing compared to their foot walls and other areas. As a result of late-stage tectonic movements, these strike-slip faults continue to develop in the thrust fault zones, which further dislocate the thrust faults. The Lan’ga fault zone presents two favorable hydrocarbon accumulation models: (1) of the main NNE-trending strike-slip faults transecting the fault-karst reservoir dipping upward, and (2) of the fault-karst reservoirs characterized by segmented hydrocarbon enrichment along the secondary NNE-trending strike-slip faults. Specifically, the hydrocarbon charging along main faults in the Hotan River structural zone underwent lateral adjustment into the secondary NNE-trending strike-slip-controlled reservoirs of fractured-vuggy type during the Late Hercynian, leading to the formation of fault-karst reservoirs, which exhibit segmented hydrocarbon accumulation along the fault zones. The NNE-directed fault-karst reservoirs in the southern anticline zone represent the favorable exploration target.

Key words: fault-karst reservoir, structural evolution, hydrocarbon accumulation model, Hotan River structural zone, Lan’ga structural zone, Bachu Uplift, Tarim Basin

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