Overpressure Prediction In Maoba And Puguang Area:a Case Study Of Jialingjiang Formation And Feixianguan Formation

The prediction of overpressure in carbonate strata is still a fundamental problem which has not been solved at home and abroad.The theoretical model and method for the prediction of overpressure in clastic strata are not suitable for carbonate strata with rigid and compact rock skeleton.Based on the data of geology,logging,drilling and seismic,the prediction model suitable for the carbonate formation pressure in Puguang Maoba area is analyzed under the isochronous stratigraphic framework,and the prediction model suitable for the carbonate formation pressure in the study area is selected.The prediction of carbonate pressure in Jialingjiang Formation and Feixianguan Formation,which are typical reservoirs in Maoba area of Puguang,has achieved good application results.By tracing and interpreting the sequence interface of carbonate rocks in Jialingjiang Formation and Feixianguan Formation(T₁j⁴⁺⁵、T₁j²、T₁j¹ of Jialingjiang Formation and T₁f ⁴、T₁f ³、T₁f ¹² of Feixianguan Formation)and tectonic mapping analysis,the study area is mainly high in southeast and low in northwest,and presents a NE-SW trending structural uplift in the middle.With the increase of buried depth,the amplitude of structural uplift is slow.Typical carbonate formation pressure prediction models are systematically analyzed and derived,including overpressure prediction model based on the relationship between volume stress variable and stress increment,formation pressure prediction model based on rock pore compression coefficient and rock pore pressure-pore volume,and formation pressure quantization model based on overpressure-effective stress-rock elastic parameter stress-strain.According to the actual geological background of the study area,a quantitative formation pressure model based on overpressure-effective stress-rock elastic parameter stress-strain is optimized,and the acquisition method and applicability of key parameters of the model are discussed.Based on the optimal carbonate formation pressure prediction model,the single well carbonate formation pressure prediction in Puguang Maoba area is carried out.The predicted results are in good agreement with the measured results.At the same time,3D seismic data is used to obtain the corresponding data of key parameters in the prediction model of carbonate formation pressure to realize the 3D seismic zone plane pressure prediction.Through comparative analysis of the measured pressure and predicted pressure results,the relative error is between 0.60%and 10.22%,and the average error is 5.87%.The predicted results are in good agreement with the measured results.The prediction results show that the average formation pressure coefficient in the Puguang area of Jialingjiang Formation and Feixianguan Formation is mainly distributed between1.1 and 1.2,which is basically normal pressure state.The pressure coefficient in the maoba area is large,and the average pressure coefficient is mainly distributed between1.4 and 1.9,which is the state of overpressure.The seismic data of key response parameters of overpressure in carbonate rocks is used to predict the pressure plane of carbonate rocks.