摘要
根据川中地区上三叠统须家河组典型气田的现今实测地层压力分析了异常高压发育的特征。以现今实测压力为约束,利用流体压实耦合方法恢复了须家河组气田主要储层的压力演化史。研究结果表明:上三叠统须家河组储层超压的发育在总体上是逐渐增大的,其地层压力演化可划分为三个阶段:(1)150 Ma之前为常压阶段,地层压力等于静水压力;(2)150 Ma至100 Ma为压力增加超压发育阶段,在100 Ma时地层压力达到最大,压力系数在1.1～1.6之间;(3)100 Ma至今为压力降低超压发育阶段,该时期地层压力及静水压力都发生明显降低,但是超压仍继续发育,演化至今压力系数在1.4～2.0之间。研究表明,烃类的充注和构造抬升剥蚀事件是川中地区异常高压的主要成因机制。
The characteristics of present abnormal high formation pressure（AHFP） in Xujiahe Formation of central Sichuan Basin were obtained based on the measured formation pressure.The formation pressure of main reservoirs obviously shows high formation pressure or AHFP at present.Bajiaochang gas field is a typical AHFP gas field with pressure coefficient between 1.7 and 2.0,while the others belong to high formation pressure gas fields with pressure coefficient between 1.2 and 1.6.This paper use coupled fluid flow compaction method to reconstruct the pressure evolution of the major reservoirs in Xujiahe Formation.This method could perfectly consider the changes of porosity,permeability and fluid volume in the reservoirs,which could perfectly reconstruct the pressure evolution history.Thermal history is a key parameter during reconstructing the pressure evolution,so this paper reconstructs thermal history by using vitrinite reflectance based on Easy% Ro model.The pressure evolution history of the major reservoirs were reconstructed according to relevant parameters and constrained in measured formation pressure.The evolution of formation pressure in Xujiahe Formation can be divided into three stages：（1） normal pressure before 150 Ma;（2） pressure increase and AHFP accumulation between 150 Ma and 100 Ma.The formation pressure and pressure coefficient gradually increased during this period.The formation pressure got to maximum with pressure coefficient between 1.1 and 1.6 at about 100 Ma;（3） pressure release but AHFP accumulation after 100 Ma.Both the formation pressure and the hydrostatic pressure decreased,but the hydrostatic pressure decreased more than formation pressure,so the pressure coefficient still increase and finally reach between 1.4 and 2.0.The origin of abnormal pressure was analyzed based on the reconstructed formation pressure incorporated burial history and maturity evolution history.It was found that the hydrocarbon charging and the hydrostatic pressure decrease during strata erosion were the main origin of AHFP,while the temperature decrease during strata erosion was main origin for the decrease of formation pressure at later period.AHFP is conducive to the hydrocarbon migration and accumulation in this area.With the characteristics of strong heterogeneity in the reservoirs,the development of AHFP was main force for hydrocarbon migration and accumulation through the dense barriers.The fluid migration is non-darcy flow in low permeable reservoir which must overcome restart pressure.In this case,the overpressure was necessary for hydrocarbon migration.The decrease of formation pressure at later period was beneficial to desolution of dissolved gas and desorption of coal bed methane in Xujiahe Formation,which enhanced the gas accumulation efficiency.To a certain extent,it reduces the requirements for gas kitchen,forming a series of large gas fields under the condition of source rock deficiency of Xujiahe Formation in central Sichuan Basin
出处
《沉积学报》
CAS
CSCD
北大核心
2011年第5期953-961,共9页
Acta Sedimentologica Sinica
基金
国家科技重大专项(编号:2008ZX05007-003-01)资助
关键词
压力演化
异常高压
四川盆地
川中地区
须家河组
pressure evolution； abnormal high formation pressure； central Sichuan Basin； Xujiahe Formation
