Miocene Reservoir Characteristics And Formation Causes Of High-quality Reservoirs In L Sag Of Qiongdongnan Basin

With the deepening of onshore exploration and research,deep water basins have gradually become the focus of exploration and research.Based on the results of previous studies,this paper takes the Miocene reservoir in L sag of deep water area in the Qiongdongnan Basin as an example.By means of X-ray diffraction,polarized light microscopy,scanning electron microscopy and hydrothermal simulation,the author has systematically studied the reservoirs in the study area from four aspects: petrology,petro physics,diagenesis and reservoir space characteristics.It is clear that the study area Layer characteristics.In addition,a series of waterrock simulation experiments were designed.Based on the reservoir characteristics in the study area,the effect of high-temperature overpressure on the reservoir quality and the main controlling factors of high-quality reservoirs were clarified.The L sag develops two sedimentary systems: the central canyon water channel and the submarine fan,which are divided into three types of temperature and pressure fields: high temperature and atmospheric pressure,high temperature overpressure,and high temperature strong overpressure.The reservoir space in the study area is mainly primary pores and secondary pores formed by corrosion.The diagenesis of the reservoir mainly includes compaction,cementation,and dissolution.Three stages of hydrocarbons and one CO2 filling are identified in the study reservoir,combining quantitative analysis of reservoir evolution of diagenetic facies,evolutionary models of different temperature and pressure field reservoirs can be obtained: high temperature and atmospheric pressure reservoir compaction pore reduction is weakened,the later siliceous dissolution provides secondary pores;high temperature overpressure and high temperature strong overpressure reservoir compaction pore reduction significantly,early feldspar and late carbonate formation of secondary porosity.By designing a series of water-rock simulation experiments of organic acids with quartz and feldspar single minerals,it was confirmed that organic acids can react with minerals to form secondary dissolution holes under high temperature and overpressure conditions.The Miocene reservoir quality in L sag is affected by diagenesis and the underground environment of hightemperature overpressure,compaction is destructive diagenesis,organic acid dissolution is the main contributor to secondary pores and is the most important constructive diagenesis of reservoirs.The high-temperature and atmospheric pressure reservoirs are mainly dominated by intergranular dissolution of quartz,while the high temperature overpressure and strong overpressure reservoirs are dominated by intragranular dissolution of feldspars.Overpressure can cause micro-fractures in reservoirs and increase reservoir porosity.High temperature can promote the dissolution of quartz and feldspar,and the higher the temperature,the greater the degree of dissolution,high temperature overpressure can also withstand the pressure of part of the overlying formation,which can effectively reduce the compaction effect,protect the primary pores and secondary pores,and effectively improve the physical properties of the reservoir.In high temperature overpressured reservoirs,organic acid dissolution is the most important constructive diagenesis,and overpressure pore retention is the most important constructive diagenesis in high temperature and overpressured reservoirs,with the increase of overpressure,the pore protection effect of overpressure increases.