Gas accumulation and great exploration breakthroughs in HTHP formations within Yinggehai-Qiongdongnan Basins

Abstract

Abstract: Through years of efforts, significant progresses have been made in gas exploration in the Yinggehai-Qiongdongnan (YQ) Basins. However, further breakthroughs in the medium-deep formations with high temperature and high pressure (HTHP) are constrained by unfavorable factors, such as poor quality data seismic, complicated geological conditions and unclear gas accumulation mechanism under HTHP conditions. In this paper, through detailed case study, the HTHP gas accumulation mechanism, main controlling factors and accumulation modes were comprehensively analyzed supported by the systematic theory of basin-forming and gas accumulation mechanisms and relevant exploration techniques under HTHP conditions in the YQ Basins. The results reveal huge gas resource potential in HTHP formations in the YQ Basins, providing abundant source basis for achieving great breakthroughs in gas exploration. Moreover, it is innovatively cognized that predominant provenances exist in structural transfer zones and unbalanced subsidence controls gravity flow distribution within strike-slip extensional basin. The theory of HTHP gas accumulation was upgraded and the HTHP gas accumulation mode of strike-slip extension controlling source and sands, hydrocarbons conducting through overpressure fissures, and multi-stage superimposition was established. The study results provide theoretical evidences for defining exploration targets in medium-large HTHP gas fields within the YQ Basins and carrying out oil and gas exploration in other HTHP basins. In recent years, some medium-large gas fields (e.g. X13-1, X13-2, L13-2, and L25-1) have been discovered and assessed successively, creating a new ground for gas exploration in HTHP formations within the YQ Basins.

Key words: Yinggehai-Qiongdongnan (YQ) Basins, high temperature and high pressure (HTHP), gas accumulation mechanism, natural gas, exploration breakthrough

Xie Yuhong, Li Xushen, Xu Xinde, Tong Chuanxin, Xiong Xiaofeng. Gas accumulation and great exploration breakthroughs in HTHP formations within Yinggehai-Qiongdongnan Basins[J]. China Petroleum Exploration, 2016, 21(4): 19-29.

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