Research Onreservoir Characteristics Of He8Section And Shan1Section Of Block Su48in The West Area Of Sulige Gas Field

This paper presents an in-depth and detailed research on the petrologic characteristics, permeability features, pore types and pore structures of paleozoic He8section and Shan1section of Block Su48in the west area of Sulige Gas Field. This study is based on core observation and relevant experiment reports. Casting thin section, scanning electron microscope, image analysis, image pore analysis, X-ray diffraction analysis, high-pressure mercury injection experiment, phase permeability experiment and cathode luminescence are applied.The reservoir performance is further analyzed. The research shows that:(1) The upper He8section and Shan1section of the target layer under research are braided delta plain deposit, and the lower He8section is delta plain deposit of meandering river. The sedimentary microfacies developed in He8section and Shan1section mainly includes distributary channel, natural levee and diara. The rocks in the reservoir are mainly lithic quartzite sandstone and quartz sandstone. Cement in the interstitial matter component mainly includes silica deposits, carbonate deposits and authigenic clay mineral, such as kaolinite and water mica. Mixed base is mainly composed of clay minerals.(2) The reservoir space of the upper He8section, lower He8section and Shan1section of the target layer under research are mainly pores, and some wells develop cracks, which are rarely seen in the whole research area. In terms of pore makeup, most primary pores disappeared in diagenetic process, and most pores are inter-granular dissolution pores. Radii of pores at different layers are of little differences. Pore combination types mainly include intergranular pore combined with dissolution pore, rock debris dissolution pore and micropore, and intergranular pore combined with intergranular micropore. Throats mainly include curved lamellar throat and bundled tubes throat, followed by lamellar throat.(3) The whole He8section and Shan1section of the target layer under research were formed in stage B of middle diagenetic phase. During rock formation, compaction, dissolution, micro fracture and cementation exerted great impact on the reservoir performance. The compaction and cementation are relatively developed in He8section and Shan1section, which will have a negative impact on the reservoir. Under strong compaction, primary pores in reservoir sandstone reduce greatly and even disappear, and reservoir performance and connectivity deteriorate. The siliceous and carbonate cements, especially the secondary quartz in sandstone, generated during cementation fill in the pores and further block the pores, deteriorating the reservoir physical properties. On the whole, the physical properties of the lower He8section are better than those of the upper He8section and Shan1section.(4) The high-pressure mercury data and capillary pressure curves reflect that He8section and Shan1section of the target layer are with high displacement pressure (valve pressure), low mercury withdrawal efficiency, large pore, throats with small radius and poor connectivity, and low water displacement efficiency. The intermediate flat section of high pressure mercury curve is not obvious, and the curves of most wells rise steeply; there is little irreducible water saturation parallel with the longitudinal axis, indicating that pore throat is of poor sorting and the rock permeability is poor. The capillary pressure curve reflects that the target layer belongs to low-permeability and extra low-permeability reservoir.