Distribution characteristics and genetic analysis of the abnormal fluid pressure in the middle Permian in the northern fault-fold zone of the western Sichuan Depression
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摘要: 含油气盆地中温压场的研究是探明油气成藏机理的核心问题,特别是古压力的恢复对研究油气的运移、聚集甚至储层的成岩、烃类的生成都起着至关重要的作用。文中以现今地层压力为约束,应用盆地模拟法恢复了川西北断褶带中二叠统的压力演化过程,并利用构造挤压应力模型定量分析超压主控因素。恢复结果显示,川西北中二叠统则发育两期超压,特别是侏罗纪—早白垩世末,受构造挤压应力作用超压快速累积,且不同构造单元受挤压应力的影响差别较大。近造山带发育弱超压,晚白垩世之后恢复至常压;远离造山带的褶皱带和前渊带则发育超压—强超压,且受侧向挤压应力的影响,构造抬升后仍然保持超压—强超压的状态。Abstract: The temperature and pressure field is the key point for studying on the mechanism of hydrocarbon accumulation in the petroliferous basin, and the reconstruction of paleo-pressure particularly plays an important role in the study of hydrocarbon migration and accumulation, and even diagenesis in reservoirs and hydrocarbon generation for source rocks. In this paper, with pressure distribution as constraint, the paleo-pressures in the middle Permian of the northwestern Sichuan Basin were reconstructed by adopting basin modeling. In the northwest fault-fold belt of the Sichuan Basin two stages of overpressure developed, in the middle Permian, especially from the late Jurassic to the end of early Cretaceous.The overpressure accumulated rapidly in reservoirs under the effect of compressive stress which varied greatly in different structural units. The weak overpressure developed near the orogenic belt, which recovered to normal pressure after the late Cretaceous; but the strong overpressure developed in the fold and foredeep zone far from the orogenic belt even after the structure uplift, which was mainly controlled by the external compressive stress from northwest.
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图 3 川西坳陷北部断褶带构造单元分布(据王鼐等,2016修改)
Figure 3. Distribution of tectonic units in the northern fault-fold zone of the western Sichuan Depression (modified after Wang et al., 2016)
表 1 中二叠统实测压力
Table 1. DST data of the Mid-Permian
井号 层位 产层中部
深度/m地层压力/
MPa压力
系数ST1 茅口组 6961.5 122.8 1.80 栖霞组 7175.0 95.6 1.36 L004-x1 茅口组 6156.0 127.9 2.12 L16 茅口组 5931.0 127.9 2.20 L17 栖霞组 5950.0 131.1 2.25 表 2 构造挤压应力对川西北地区地层压力的贡献量
Table 2. Contribution of tectonic compressive stress to the formation pressure in the northwestern Sichuan Basin
时间 平均构造应力/
MPa孔隙度/
%密度/
(g·cm-3)泊松比 超压
贡献率/%增压大小/
MPa印支运动晚幕 19.5 5 2.66 0.22 92 17.99 燕山运动早-中幕 60.9 3.5 2.66 0.22 94 57.52 燕山运动晚幕 32.8 3 2.66 0.22 95 32.23 喜山运动早幕 36.5 2.5 2.66 0.22 96 35.03 喜山运动晚幕 41.5 2.1 2.66 0.22 97 40.09 平均构造应力数据操成杰,2005;孔隙度为下文典型单井盆地模拟结果 表 3 川西北地区中二叠统温度降低量及其引起的压力下降幅度
Table 3. Pressure reduction caused by temperature reduction in the Mid-Permian in the northwestern Sichuan Basin
井名 ΔT/℃ ΔPt/MPa Ph/MPa P0/MPa Pmax/MPa ΔP/MPa GJ 57.7 62.1 72.7 108.5 149.9 41.4 L4 60.4 64.9 61.1 93.8 126.5 32.7 B1 57.1 61.5 55.6 71.7 105.0 33.3 S1 76.3 82.1 61.0 78.9 138.7 59.8 K3 66.5 71.6 35.9 34.9 69.6 34.7 注:ΔT=最高古地温-现今温度;ΔPt=ΔT×1.076 MPa/℃ (刘一锋等,2015);Ph为静水压力;P0为现今压力;Pmax为盆地模拟得到最大古压力;ΔP=Pmax-P0 -
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