陕北富县探区延长组长3储层特征及评价

陕北富县探区延长组长3油层为该区的主力产层之一。长3油层属于三角洲前缘亚相沉积环境,其储层的主要成因类型为水下分流河道砂体、河口坝砂体,次为前缘席状砂和远砂坝。通过对80个样品的统计及分析,储层的矿物成分成熟度低,结构成熟度中等—好。储层的成岩作用类型繁多,但主要以压实及压溶作用、胶结作用和溶解作用为主,且主要处于晚成岩阶段的A期,成岩演化阶段分为3个:压实作用及粘土矿物胶结孔隙缩小期、胶结充填孔隙缩小期及溶解作用孔隙扩大期。通过对18口井1 683块样品的物性分析资料的分析,长3油层属于低孔—特低渗储层,孔隙类型以剩余粒间孔、粒内溶蚀孔为主。储层主要受沉积作用和成岩作用的影响。根据以上资料,把长3油层划分为好、中、差三类储层,长3~2的物性较好;长3~1、长3~3的物性较差。

Characteristic and Evaluation of Chang 3 Member Reservoir of the Yanchang Formation in the Fuxian Area, North Shaanxi

The oil-bearing Chang-3 member of the Yanchang Formation is one of the major oil producing formations in the Fuxian area,north Shaanxi.Chang-3 member belongs to an environment of delta frontal subfacies.The primary types of the reservoirs include distributary channel sandbodies,river mouth bar sandbodies.The secondary types are front-mat sand and distal bars.Statistics and analysis for 80 simples indicate that mineral maturity of Chang 3 reservoir is low,and textural maturity is medium-low.Reservoir diagensis types are relatively comlex and mainly consist of compaction,cementation and dissolution in the A period of the late stage.Diagenesis evolution can be divided into three stages:compaction and cementation to pore reduction,cementation,infilling and pore reduction and corrosion to pore enlargement.Petrophysical property analyses of 1747 simples from 18 wells show that the physical property of the Chang-3 member reservoir is of low porosity and very low permeable reservoir.Pore types are characterized by residual protozoal intergranular porosity and dissolution porosity.The reservoir is closely controlled by sedimentation and diagenesis.It is suggested that the Chang-3 reservoir can be divided into the high quality excellent,the intermediate quality and the low quality reservoirs.The physical property of the Chang3~2 reservoir is bettern that Chang3~1 and Chang 3~3.