惠民凹陷中央隆起带异常低压特征及成因分析
Subnormal Pressure Characteristics and Genesis Analysis of the Central Uplift Belt in Huimin Sag

摘要： 惠民凹陷普遍存在异常低压现象，低压发育层段为沙河街组二段、三段，且集中分布在中央隆起带周边。前人对异常低压成因研究尚存在于定性描述阶段，应用295口井试油实测地层压力数据，分析了惠民凹陷地层压力纵向、平面分布特征；从引起异常低压主要因素入手，定量分析了抬升地层剥蚀、地层温度降低、蚀变耗水作用、蚀变矿物体积变化对地层压力的影响。结果表明，地层剥蚀孔隙反弹引起地层压力降低0516 MPa；地温下降造成地层压力降低202~373 MPa；蚀变耗水引起地层压力降低864 MPa；蚀变矿物体积变化使得地层压力降低436 MPa；成藏期烃类充注，地层压力增加量小于32 MPa。以上各因素共同作用，使得中央隆起带压力演化呈现降压-增压-降压的旋回性，并最终形成现今压力分布格局。
Abstract: There commonly developed subnormal pressure in Huimin Sag, which mainly located in the second and third members of Shahejie Formation vertically and around the Central Uplift Belt horizontally. The previous studies on genesis of subnormal pressure has still remained unquantitative. Based on the measured data of 295 boreholes, the vertical and horizontal distribution characteristics of the strata pressure in Huimin Sag were discussed. Furthermore, the decrease of pressure caused by the influence of the strata denudation, temperature decrease, water consumption of mineral alteration and volume change of minerals was analyzed quantitatively, which was respectively 0516 MPa, 202 to 373 MPa, 864 MPa and 436 MPa. Hydrocarbon filling led the pressure increased less than 32 MPa. All the above factors together made that the pressure evolution of Central Uplift Belt presented the cycle of depressurizationpressurizationdepressurization, and finally formed the current distribution characteristics of pressure