Diagenetic Field Analysis And Porosity Prediction Of Gaotaizi Reservoir In Northern Songliao Basin

In order to evaluate the reservoir quality of the Gaotaizi reservoir in northern Songliao Basin,the effects of time,temperature,diagenetic fluid and pressure were taken into account.Combining the original Diagenetic Modeling System,this model was improved and the numerical value of diagenesis was recompiled.The diagenetic evolution numerical simulation and reservoir porosity prediction of the Gaotaizi reservoir in northern Songliao Basin were carried out by applying the updated simulation system.Through the analysis of diagenesis of mudstone and sandstone and the division of diagenetic stage,the diagenetic law of the study area shows that the diagenesis has become stronger from the edge to the sedimentary center.Based on this,the diagenetic field analysis shows that: At the end of the Nenjiang deposition period,hydrocarbon source rocks began to generate oil and gas.At this time,the Gaotaizi reservoir entered in the sub-period of the middle diagenetic stage A1,in which secondary pores developed,structural traps have taken shape,and the original oil and gas reservoirs began to form;The source rock of the first member of the Ming Dynasty is mainly in the A21,and the reservoir of the Gaotaizi reservoir is mainly in the middle A1.The structural trap has basically been established,and large-scale accumulation of oil and gas is basically completed.Nowadays the basic state of the late K2 m is maintained,On the plane distribution,it basically entered the A21 in Qijia-Gulong Depression,Daqing Placanticline,and Sanzhao Depression,and the bottom of the Gaotaizi reservoir in the Qijia-Gulong Depression has even entered in the A22,primarily including secondary pores,massive cracks,in which the organic matter maturity is in the stage of maturity or high maturity.After analyzing the reservoir physical factors,we take full account of the two main controlling factors of sedimentary facies and diagenesis.Based on the comprehensive consideration of these two main control factors,the method of controlling variables is adopted.The change of porosity of different diagenesis under the same sedimentary conditions and different sedimentary facies under the same diagenesis are discussed.The multivariate porosity prediction model is obtained by post-fitting.The prediction of this model shows that the porosity distribution has certain similarities,due to the deeper burial of the two depressions and the finer grain size,each layer of reservoir porosity isolines gradually decreases along the periphery of the basin toward Sanzhao Depression and Qijia-Gulong Depression.From bottom to top,the porosity of reservoirs in each interval gradually increases,and the range of tight reservoirs gradually decreases.At present,themiddle and bottom parts of the Gaotaizi reservoir are all densify in the Central Depression.Based on the simulation of the development history of single well porosity,we combined with the temperature measurement data of fluid inclusions and then it was confirmed that the compact time of Gaotaizi Reservoir in Qijia-Gulong Depression was earlier than the accumulation time.Therefore,oil and gas are not controlled by structural traps,which are mainly distributed in high-quality reservoirs adjacent to source rocks.