Study On The Integrity Of CO₂ Storage Formation Under Chemical-Seepage-Stress Action

With CO₂ flooding and the continuous expansion of storage,on the one hand,the CO₂injection formation after will change the stress state of the rock stratum,on the other hand the CO₂ dissolves in water to form acid fluid in formation rock dissolution,changed the macro and micro composition of formation rock mechanical characteristics,in these two aspects together under the action of the CO₂ injection zone formation can maintain integrity,should cause enough attention,also decided to CO₂ flooding and storage project success or failure of the key factors.By combining laboratory experiments with numerical simulation,this paper reveals the microscopic mechanism of the water-rock reaction between CO₂ displacement and the conditions of storage and storage,and expounds the change rules of the microscopic mineral composition,pore characteristics and macroscopic mechanical parameters of the reservoir and interlayer rocks during the process of CO₂ displacement and storage.This paper explains the formation integrity failure phenomenon caused by CO₂ sequestration with the increase of storage time,and presents an evaluation method for formation integrity considering the combined action of chemical-percolation-stress multiple physical fields,which provides a theoretical basis for the evaluation of formation integrity in the process of CO₂ displacement and storage.Research contents mainly include:?1?By analyzing the reaction process between rock minerals and CO₂ aqueous solution and the transformation relationship between each mineral,the microscopic reaction mechanism of rock minerals in the process of CO₂ storage was clarified.According to the variation trend of the secondary pore structure of reservoir rocks under the action of dissolution,the CO₂-water-rock dynamic reaction model was established by introducing the parameters of the solid-specific surface area.Based on the reaction characteristics of rock dissolution and precipitation,and based on the transition state theory,the evolution model of rock porosity and permeability characteristics in the process of dynamic reaction was established by combining the material migration and chemical reaction terms.?2?The rock static corrosion experiment and dynamic displacement experiment,through the determination of mineral composition and microstructure observation,reveals the change on the rock phase transformation in the process of mineral components of pore characteristics,the influence of rock quantitative evaluation after CO₂ solution chemistry,the change rule of permeability of rock in numerical simulation for CO₂ flooding process and formation integrity evaluation of initial parameters at the same time,the dynamic response under the condition of rock permeability characteristics of the evolution model experiment.?3?The numerical simulation of the water-rock dynamic reaction in the process of CO₂ oil displacement and storage was carried out under the WAG working conditions in the field,and the variation rules of mineral content,porosity and permeability characteristics and storage capacity of the reservoir and interlayer rocks were obtained,so as to clarify the carbon sequestration effect of each mineral component in the stratum during the process of storage.It provides the necessary parameters for the numerical simulation of formation integrity under the action of chemical-seepage and mechanics,and provides the theoretical basis for the research of formation integrity failure mode.?4?Considering chemical-seepage and stress is a combination of physical fields,based on the damage mechanics theory,through the dynamic response of porosity in the process of change to reflect the mesoscopic structure of rock damage degree,established a dynamic response model of petrophysical parameters in the process of evolution,micro dissolution reaction conditions for the quantitative characterization of petrophysical parameters evolution;Aiming at the CO₂ storage area in Hei79,a dynamic evaluation method of formation integrity changing with time was proposed from two aspects of microscopic sealing mechanism and macroscopic mechanical failure,and the evaluation process of formation closure was improved.