Analysis Of Reservoir Physical Properties Under Controlling By Sedimentary Facies And Diagenesis

In recent years, the oil & gas production of The Changqing Oil Field has exceeded that of the Daqing Oil Field, thus hydrocarbon yield of the Changqing Oil Field has already been the number one in the CNPC, especially the nature gas yield increasing catches people’s eyes. The Sulige Gas Field is one of the focused gas fields for exploration and development of the Changqing Oil Field, which has been the largest gas field in our country. The study area is located in the south of Sulige Gas Field, the exploration and research on the HE 8 and SHAN 1 hydrocarbon-bearing Groups of the Permian, Upper Paleozoic is relatively weak at present. The sedimentary facies, characteristics of the sandstone reservoir petrology, porosity and permeability, diagenesis of the HE 8 and SHAN 1 Group are studied in this paper, based on the observation of drilling cores, well logging interpretation, identification and quantitative statistics of the skeleton and cement minerals from conventional thin sections and casting thin sections under microscope, electron microscope scanning, measurement of homogenization temperature of the diagenetic fluid inclusions, porosity and permeability.The research results reveal that the depositional environment of during the SHAN 1 period was meandering-river delta front in the south of Sulige Gas Field, the HE 8 sedimentary period was belong to braided-river delta plain in the northern part, and braided-river delta front in the study area, respectively. The sandstone types of HE 8 and SHAN 1 are mainly quartzarenite and litharenite, Dissolution pores are the major pore type in the sandstone reservoir, but occurred often companied with the other pore type such as primary intergranular pores, intercrystal micropores, microfissures and cracks, resulting in mult-pore assemblage, among these pore assemblages, the assemblage of primary intergranular pores+ dissolution pores+ intercrystal micropores is the best one in the HE 8 and SHAN 1 sandstone reservoirs. Diagenesis of the reservoirs mainly include mechanical compaction, cementation (including silica, clay minerals, calcite cementation), metasomasis and dissolution. The HE 8 and SHAN 1 reservoirs of the study area have entered the middle diagenetic A period as a whole.Depositional facies controls the spatial distribution of sand body, is also the reflection of the hydrodynamic conditions, which is the original factor affecting the reservoir physical property. The porosity and permeability of sandbodies are different varying with different sedimentary microfacies. Quality of sandbody in distributary channel and subaqueous distributary channel is much better. The horizontal distribution of porosity and permeability is controlled by the distribution of microfacies:quality of sandstones distributed in the middle part of the distributary channels and the subaqueous distributary channels is the best, followed by the sandbodies in the edge of the channels. Diagenesis, on the basis of original deposition, has great influence on the reservoir physical properties. In the diagenesis, compaction and cementation are the main factors which resulted in the low porosity and low to very low permeability reservoirs, while dissolution increased the porosity of reservoirs, improving the reservoir quality greatly.