Study Of Simulation Experiment On Carbonate Reservoir Dissolution And Reconstruction By Acid Fluid

Through the experiments of acid fluids in carbonate erosion under the burial environment with the method of carbonate dissolution experiment,we can not only know the conditions,processes and controlling factors clearly of the experiments,we can also know the quantitative data about the formation of hole,minerals(crystals or particles)coming from carbonate erosion and the characters of the evolution of hole features.By discussing the relationships between the character of rocks,types of acid fluids,the temperature of stratum,pressure and other factors with the burial erosion of carbonate,combined with the variation of rock permeability,to evaluate the effect of reservoir reconstruction,which providing technical supports for the oil and gas exploration.In this experiment,we use the water-rock reaction simulation device,to simulate the erosion reaction and the fluid flow process in rocks between different types of dolomite and limestone with deionized water and organic acid solution,according to the actual burial environment of the Feixianguan Group,Changxing Formation,Sichuan Basin.This experiment is divided into four batches.We calculate the amount of rock erosion and permeability changes of each batch,we also use the CT and SEM to analyze the erosion characters of the minerals and holes in the internal or surface of rock.We analyze the variation of elements and minerals during the process of erosion reaction by testing the composition and content of elements of the exudates solution.Through the four batches of experimental study under the burial condition,the conclusions achieved are as follows:the water-rock reactions between fluids and rocks are important way of reservoir reconstruction.The rate of dissolution,the content ratio of Ca and Mg in solution and core permeability have the same variation.The effect of different fluids in reservoir reconstruction is different.The deionized water can reduce the core permeability,2.5g/L acetic acid solution increase the core permeability,the effect of transformation of acetic acid on dolomite is better than limestone.Most of the dissolved minerals in solution is CaCO3.The dissolution rate,permeability and content ratio of Ca and Mg are increasing when the experimental temperature increases during the temperature and pressure range of 50-150 ? and 0.5-22.5 MPa.The content ratio of Ca and Mg is close to balance when the difference of experimental pressure is 20MPa to 22.5MPa.This paper also discussed the changes of the temperature and pressure which influence the transformation of the reservoir,compared the different pressure regulation between the buried condition and underhypergene condition.