Research On Diagenesis And Reservoir Characteristics In The He-8 And Shan-1 Member In West Sulige Gas Field Of Ordos Basin

Due to distribution of sand body and very variety of reservoir physical characteristics and serious nonuniformity at the Sulige gas field, the article eyes on the problems existing in this area, under the guidance of sedimentology and oil geology theories, deeply research for the sedimentary facies, diagenesis and reservoir characteristics by means of many tests and analyses. Then the study seted up the model of the form and evolvement of raservoir, divided the diagenetie facies, studied the regulation of distribution. On the foundation of preliminary study, the paper analysised the controlling factors on development of reservoir,forecast the avail area for reservoir upgrowth.After the comprehensive research of the diagenesis characteristies,pore strueture characteristics,physical properties characteristics of the main gas bearing strata H8 and Shan1 reservoir of west Sulige gas field of Ordos Basin, holds that:During the sedimentary period of Shan-1 Formation, the sedimentary fades pattern was the meandering fluvial-delta deposit,which showed a sedimentary differentiation from north to south. During the sedimentary period of Member 8 of Xiashihezi Formation,the alluvial system migrated into the south of the study area widely and formed the fluvial-delta deposit,in which the braided fluvial was dominant.The results of reservoir petrology in west Sulige area show that:the quartzose standstone and lithic quartz sandstone are the mainly reservoir rock types of the west Sulige area.The type of detrital minerals has high quartzose and lithic quartz content,low feldspar content,with middle to slightly low compositional maturity.And the Argillaceous matrix. ferruginous calcite, siliceous are the mainly interstitial material tapy ,the tuffaceous and margin chlorite could be observed in some wells. During the mainly diagenesis types: The dissolution and fracture diagenesis functions are the main reasons of increasing reservoir quality. While the compaction,cementation and metasomatic alteration are the main reason of deceasing reservoir. According to the association type sand evolutionary sequences of the diagenesis pattern , it is concluded that the diagenetic evolution of He 8 and Shan 1 sandstone has already been in stage B of the middle diagenetic stage. Based on the analysis on diagenesis and reservoir petrology , the research area has be divided into five different diagenetic facies. Relatively the dissolution and cementation , facies combination belongs to the favorable reservoir.The mixed pore with remnants primary pore and secondary pore are the important pore-types of the west Sulige area reservoir. The reservoir with bad physical property is always low-porosity and low-permeability, individual is middle-porosity and low-permeability. So the reservoir pore texture is less. According to parameters of physical property and characters of mercury penetration,the reservoir is divided into four types. The west sulige gas field main belong to middle reservoirs.Then, the article comprehensive analysed the factors of reservoir develop on the basis of primeval sediments, deposition and diagenesis. According to the fomer reservoir classification of the porosity, permeability, gas saturation and absolute open flow of gas during reservoir testing, the synthetical reservoir classification has been proposed Basin on this scheme, the west sulige area mainly ascribed to middle-low reservoirs.and what is more,The channel sand body is favorable reservoir in Sulige area.