胜北洼陷三间房组致密砂岩气藏有利储层特征与成岩相

Favorable reservoir characteristics and diagenetic facies of tight sandstone gas reservoir of Sanjianfang Formation in Shengbei Subsag

吐哈盆地台北凹陷胜北洼陷中侏罗统三间房组发育致密砂岩凝析气藏,油气勘探潜力巨大。通过岩心描述、薄片观察、扫描电镜分析等手段,系统分析了胜北洼陷三间房组的沉积和储层特征,开展成岩作用与成岩相研究。研究表明:胜北洼陷三间房组储层岩石类型为长石岩屑砂岩(约占70%)和岩屑砂岩(约占30%),为强非均质性特低孔-特低渗致密砂岩储层;以细砂岩为主,颗粒支撑,孔隙型胶结,成分和结构成熟度都较低,储层砂岩以压实、胶结等成岩作用为主;储层物性是气藏富集的关键因素,主要受成岩作用和沉积微相类型影响,绿泥石胶结和成岩后期裂缝改造是优质储层发育的重要特征;三间房组二、三段为储层发育有利层段,共发育4种成岩相类型,其中有利于有效储层发育的成岩相有2种,分别为绿泥石-粒间孔成岩相和高岭石-溶蚀孔、粒间孔成岩相。

Tight sandstone condensate gas reservoirs are developed in the Middle Jurassic Sanjianfang Formation in Shengbei Subsag,Taibei Sag, Tuha Basin, with huge oil and gas exploration potential. The sedimentary and reservoir characteristics of Sanjianfang Formation in Shengbei Subsag are systematically analyzed by means of core description, thin section observation, scanning electron microscope analysis, and the study of diagenesis and diagenetic facies is carried out. The results show that the reservoir rock types of Sanjianfang Formation in Shengbei Subsag are feldspathic lithic sandstone(about 70%) and lithic sandstone(about 30%), which are tight sandstone reservoirs with strong heterogeneity, ultra-low porosity and ultra-low permeability. It is dominated by fine sandstones, supported by grains, cemented by pores, with low composition and texture maturity. The reservoir sandstones are mainly diagenetic processes such as compaction and cementation. Reservoir physical property is the key factor for gas reservoir enrichment, which is mainly affected by diagenesis and sedimentary microfacies types. Chlorite cementation and post diagenetic fracture reconstruction are important characteristics of high-quality reservoir development. The second and third members of Sanjianfang Formation are favorable for reservoir development, and there are 4 types of diagenetic facies developed. Among them there are 2 diagenetic facies favorable for effective reservoir development, namely chlorite-intergranular pores diagenetic facies and kaolinite-dissolution pores and intergranular pores diagenetic facies.