Oil & Gas Geology ›› 2025, Vol. 46 ›› Issue (1): 151-166.doi: 10.11743/ogg20250111

• Petroleum Geology • Previous Articles     Next Articles

Genetic mechanisms of high-quality deep to ultra-deep clastic reservoirs: A case study of the Permian-Triassic strata in the hinterland of the Junggar Basin

Jiyuan WANG1,2(), Bin WANG1,2(), Zongquan HU3, Fengkai SHANG4, Dezhi LIU4, Zhenming LI1,2, Qi QIU1,2, Zhenxiang SONG1,2, Zhiqi HU5   

  1. 1.Wuxi Institute of Petroleum Geology,Petroleum Exploration and Production Research Institute,SINOPEC,Wuxi,Jiangsu 214126,China
    2.Key Laboratory of Hydrocarbon Accumulation,SINOPEC,Wuxi,Jiangsu 214126,China
    3.Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 102206,China
    4.Exploration and Development Research Institute,Shengli Oilfield Branch Company,SINOPEC,Dongying,Shandong 257001,China
    5.School of Earth Resources,China University of Geosciences (Wuhan),Wuhan,Hubei 430074,China
  • Received:2024-07-09 Revised:2024-11-10 Online:2025-02-28 Published:2025-03-03
  • Contact: Bin WANG E-mail:wangjy1992.syky@sinopec.com;wangbin.syky@sinopec.com

Abstract:

This study aims to reveal the genetic mechanisms underlying high-quality deep to ultra-deep clastic reservoirs in the hinterland of the Junggar Basin. Using the latest drilling data and core samples from the hinterland, as well as data from casting thin section observations, scanning electron microscopy (SEM), spectral analysis, inclusion analysis, and X-ray diffraction (XRD) analysis, we investigate the origins of reservoirs in the Permian Upper Urho Formation and the Triassic Baikouquan and Karamay formations. The results indicate that differential diagenetic evolution governs the development of primary pores and secondary dissolution pores. The Karamay Formation underwent compaction, chlorite coating cementation, dissolution of feldspar/volcanic detritus, siliceous cementation, authigenic illite precipitation, and the late-stage calcite cementation sequentially, during which chlorite coatings emerged as the most significant diagenetic mineral for the preservation of primary pores. In contrast, the Upper Urho Formation experienced compaction, chlorite filling cementation, laumontite cementation, dissolution of laumontite/feldspar/volcanic detritus, siliceous cementation, authigenic illite precipitation, and the late-stage calcite cementation in sequence. The early-stage laumontite cementation and acid dissolution of laumontite/feldspar/volcanic detritus, among others, play a critical role in the formation of secondary pores. In the subaqueous distributary channels at the front of the shallow braided river delta, the strong hydrodynamic elutriation in high-energy facies zones results in superior primary pore structures in these reservoirs. This, combined with early-stage chlorite coatings and significant overpressure, collectively contributes to the preservation of primary pores. The early-stage cementation of high-hardness laumontite formed by the hydrothermal alteration of intermediate-mafic volcanic detritus resists the compaction and porosity reduction in the rapid deep burial stage. The acidic fluids from multi-stage hydrocarbon generation and overpressure transfer jointly accelerate the dissolution of aluminosilicate minerals and porosity enhancement. Under the background of low geotemperature, the Upper Urho-Baikouquan formations remain in middle diagenetic stages A and B, which has slowed down the diagenetic evolution and increased the lower depth limit for effective porosity development.

Key words: genetic mechanism, high-quality reservoir, deep to ultra-deep strata, Upper Urho Formation, Baikouquan Formation, Karamay Formation, Junggar Basin

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