川中公山庙构造沙一段油藏成藏条件

MEMBER SHA-1OIL RESERVOIR FORMATION CONDITIONS OF GONGSHANMIAO STRUCT URE IN CENTRAL SICHUAN

公山庙构造是目前川中油气勘探的一个重点区块 ,该区侏罗系沙溪庙组沙一段油藏是西南油气田分公司“九五”期间原油勘探的重大发现。该油藏是构造—岩性复合油藏。通过对沙一段油藏成藏条件的系统深入分析 ,认为储层及油源通道是成藏的关键。油源主要来自下伏凉高山组烃源层 ,源岩厚度大 ,有机质含量高 ,烃源丰富 ,为沙一段油气富集提供了雄厚的物质基础。储层为低孔渗、致密、非均质性极强的薄层裂缝—孔隙型砂岩储层。受沉积体系演化的控制 ,多类型的储集砂体在纵横向相互叠置 ,从而导致储集砂体的集中发育 ,为油气富集提供了有利的储集条件。断裂发育极大地改善了储层的渗流能力 ,是影响产能的关键 ,并且为油气运聚提供了重要的通道。综合分析提出了“储集砂层与断裂并重”的勘探指导思想 ,并且指出勘探中应注意 :①沙一段底部砂层的稳定性及其品质的差异性 ;②沙一段中上部河道的多样性、垂向叠加性及侧向迁移性。

Gongshanmiao structure is a key tract of oil a nd gas exploration in Cen tral Sichuan at present.In the region,the member Sha 1 oil reservoir in Shaxima o Formation of Jurassic was an important discovery of oil exploration achieved b y the Southwest Oil and Gas Field Branch,PCL,during the Ninth'Five Year'Plan ,being a structural lithologic combination trap.Through systematically analyzin g its formation conditions,it is considered that the key conditions of reservoir form ation are oil source,reservoir bed and migration pathway.The oil source bed is m ainly the underlying Lianggaoshan Formation which has a large oil source rock th ick,high organic matter content and abundant hydrocarbon source,thus providing r ich material base for oil and gas accumulation in member Sha 1;reservoir bed is a tight,ultra heterogeneity,thin,fracture pore sandstone reservoir with low po rosity and low permeability,and controlled by sedimentary system evolution,many types of reservoir sandbodies were inter superposed with each other in vertical and lateral,thus providing beneficial storage condition for oil and gas accumula tion owing to the concentrated growth of reservoir sandbodies;and the well deve l oped faults not only greatly improved the percolation flow capacity of the reser voir,which is the key of influencing deliverability of the reservoir,but also pr ovided important pathways for oil and gas migration and accumulation.By means of comprehensive analysis it is proposed that'laying equal stress on reservoir s andbody and fault'is the thought of guiding exploration;and in exploration we s hould pay attention to ① the stability of the sandbodies at the bottom of memb er Sha 1 and the diversity of its quality,and ② the variety,superposed propert y,removability and heterogeneity of the channel sandbodies in the middle and on the top parts of member Sha 1.