High Quality Reservoir Controlling Factors Of The Shahejie Formation-4 In Bonan Sag

With the further deepening of exploration,deep oil and gas exploration has become the focus of the petroleum industry,mainly refers to the deep oil and gas exploration of new strata,new fields.Because of the lack of deep drilling data,logging data and geochemical data at that time,the research on the factors of sedimentary system is relatively lagging behind,which further limits the exploration and development of the study area.Factors such as sedimentary environment,formation pressure,diagenesis,gypsum and other factors control the development of high quality deep reservoirs in the Shahejie Formation-4 of the Bonan sag,making the conditions for developing high-quality reservoirs extremely complex.It further restricts the research work of deep layer high quality reservoir.Although progress has been made in deep exploration of oil and gas,the success rate of exploration is low.In order to strengthen the research in this field,this paper,on the basis of collecting and arranging the previous data and recognizing the geological background of the study area,through drilling,core observation,sample analysis and testing(sections cut from cores identification,physical properties,temperature,etc.)From the aspects of petrological characteristics,reservoir physical properties,reservoir space types,diagenesis and so on,the reservoir characteristics of the Shahejie Formation-4 in Bonan sag are recognized.It is of great theoretical and practical significance for deep oil and gas exploration to discuss the controlling factors of the development of high-quality reservoirs in the Shahejie Formation-4 in Bonan sag.The rock types of the Shahejie Formation-4 in Bonan sag are mainly unequal grain sandstone,medium coarse sandstone or gravel sandstone,fine conglomerate.Generally speaking,the Shahejie Formation-4 in Bonan sag is low porosity and low permeability.The primary pores are mostly destroyed and the unfilled fractures are effective migration channels.The main types of deep reservoir space in Bonan sag are three kinds of dissolved pores,three kinds of fractures and the composite system of pore fractures.The results show that the diagenesis which has important influence on reservoir development has compaction cementation metasomatism and dissolution.The salt water lacustrine system was mainly developed in the sedimentary period of the Shahejie Formation-4,the shallow lake basin system was dominant in the lower member 4 of Shahejie Formation,and the deep water lake basin system was the main system in the upper member 4 of Shahejie Formation.The development of the salt lake basin resulted in the precipitation of brine to form the gypsum strata.The sediments experienced alkaline diagenetic environment in the early stage.The development of gypsum formation should be one of the reasons for the difference of reservoir physical properties in Shahejie Formation-4 in each structural block.Abnormal pressure has a strong influence and control on reservoir physical properties.Overpressure and deep reservoir with good physical properties in the vertical and plane matching.Based on the analysis of the effective reservoir control factors in the Shahejie 4 Formation of the Bonan sag,it can be seen that sedimentation,diagenesis,formation pressure and gypsum have important influence on the development of deep effective reservoir.