Experimental Study Of Water Invasion And Gas Injection For Water Control In The Main Reservoir Of Puguang Gas Field

The Puguang gas reservoir is the largest carbonate gas reservoir in China.With the development of the gas reservoir,the main gas reservoir in Puguang has experienced edge and bottom water intrusion or even water flooding during the production process.At the same time,the drop in formation pressure has intensified the flow of formation fluids.complexity.Therefore,the exploration of gas injection and water control technology and its mechanism has important guiding significance for the efficient development of such gas reservoirs.In this thesis,the experimental method of the diffusion law of indoor supercritical CO₂ system in formation fluid and the physical simulation experimental method of edge-bottom water-driven multi-row well gas production were established,and the comparative study of different development methods was carried out to reveal the edge and bottom of carbonate gas reservoirs.The law of water and water influx;by carrying out CO₂ injection water control experiments,the changes in gas and water production characteristics influenced by multiple factors were analyzed,and the mechanism of CO₂ injection water control was explored.The experimental results show that,under bulk conditions,the diffusion coefficient of CO₂-formation water system and CO₂-CH₄ system is positively correlated with the pressure drop;with the increase of system pressure,the diffusion coefficient shows an upward trend;The rate of diffusion;under the condition of porous media,the diffusion coefficients of CO₂-formation water system and CO₂-CH₄ system are also positively correlated with the pressure difference,but compared with bulk conditions,diffusion is more difficult to proceed.The diffusion coefficients of CO₂ in the formation water system and CH₄ system are both in the order of 10^-8,indicating that the diffusion rate of CO₂ is very slow under reservoir conditions,and it can exist in the formation as a single phase to form an effective sealing strip.The edge and bottom water intrusion of the tandem core model can be divided into four stages:the slow seepage stage of edge water,the stable seepage stage of edge water,the stage of water breakthrough and the stage of complete flooding.The optimal gas injection rate range for water control should make the formation pressure recovery level not lower than 66%,and the recovery factor increase by about 21.6%-26.6%;when the water is completely flooded,inject CO₂ to control water,which can prolong the production cycle of gas wells and reduce gas wells.waste pressure.The experimental results of gas injection and water control in the parallel core model show that after CO₂ injection,part of the water in the high-permeability core can be connected to lock gas,but the high-permeability core will see water quickly,and the final recovery rate increases by 5.1%;CO₂ can form an effective isolation zone,delay water channeling,and increase the ultimate recovery factor by 6.6%.Combined with the analysis of the water intrusion law and the characteristic changes of gas production and water,the gas production during the water intrusion law can be divided into four stages:the uniform gas production stage,the gas production increase stage,the gas production decline stage,and the single-phase flow stage.;The mechanism of CO₂injection to control water and enhance oil recovery can be divided into three aspects:communication of water to lock gas,delay of water channeling,and CO₂ injection to enhance energy replacement.