川中--川南地区上三叠统须家河组气藏异常压力分布及成因

通过对川中--川南地区须家河组气藏异常压力的纵向和平面分布特征研究,结合沉积背景、构造演化和生烃作用等分析了异常高压的成因;并利用剥蚀量、流体包裹体均一温度及改进的Lee--Kesler状态方程识别了古今地温差与剥蚀厚度及其与压力系数之间的关系。川中--川南须家河组各储层段压力系数在平面上由西北向南逐渐降低,纵向上呈常压(压力系数0.90～1.1)、高压(压力系数1.1～1.4)及超高压(压力系数1.4)三段式分布。生烃增压和储层的致密化是本区产生异常高压的主要原因。各气藏古今地温差为35℃～70℃,古今地温差与剥蚀厚度呈正相关关系、与压力系数呈负相关关系,说明川中--川南须家河组现今压力分布状态是地层抬升剥蚀造成的。

Distribution and origin of abnormal pressure in Upper Triassic Xujiahe Formation reservoir in central and southern Sichuan

Through the research of longitudinal and plane distribution characteristics of abnormal pressure in Xujiahe Formation reservoirs in central and southern Sichuan,the authors analyzed the causes of abnormal high pressure combining with sedimentary background,structural evolution and hydrocarbon generation,and recognized the relationships between ancient and mordern geothermal difference with denudation thickness and pressure coefficients utilizing denudation thickness,homogenization temperature of fluid inclusions and improved Lee-Kesler state equation. The pressure coefficients of the Xujiahe Formation reservoirs decreased in the plane from northwest to south,and appeared to be three-staged in distribution vertically including normal pressure （coefficient as 0. 90 ～ 1. 1）,high pressure （coefficient as 1. 1 ～ 1. 4） and superhigh pressure （as coefficient 〉1. 4）. The generation pressurization of hydrocarbon and densification of reservoir are the main reasons of abnormal high pressure. The ancient and mordern geothermal difference of gas reservoir is 35℃ ～ 70℃,and the ancient and mordern geothermal difference is positive relation with denudation thickness and negative with pressure coefficient. The fact shows the present pressure distribution in the Xujiahe Formation in central and southern Sichuan is caused by the uplift anddenudation of strata.