Researches On Temporary Plugging Technology In Fracturingfractures For Tapping The Potential Of Old Wells In Penglaizhen Formation In Western Sichuan

The tight sandstone gas reservoirs majority of oil and gas wells are in late stage of development in western,output enter decreasing period.The measures of increase production are increasing to tapping the potential of old wells.In the killing process,kill fluid will flow the high flow capable steady fractures into the reservoirs in old well turn-tier development.Not only the kill fluid's outflow will cause unstability of killing process,but also it will lead to seriously pollute gas reservoirs and reduce oil and gas production.Therefore,the study of formation damage the killing fluid cause when turn-tier development,and development of reservoir protection and temporary plugging killing fluid will become one of the key technologies of efficient development of fractured oil and gas resources.Penglaizhen formation gas reservoirs in western Sichuan is the tight sandstone gas reservoirs,the feature are the poor reservoir properties,non-homogeneous distribution of intensity,small size pore and throat and bundle types throat.Types of clay minerals are rich,its occurrence division structure exists instability,which lead to have potential damage that particles are dispersed and migrated,water is trapped,treatment agents are absorbed and retained in the gas resources.Current killing fluid can not form intact temporary plugging layer for the steady fractures.Therefore killing fluid outflow into reservoirs seriously.Papers to steady fractures in turn-tier development as the protection object,as the background to the special engineering geological characteristics of the work area.on the basis of previous studies by reservoir sensitivity experiment,capillaries self-absorption and water trapped experiment and solid particles damage experiment and so on to study gas reservoirs damage mechanism.And,by narrowly measuring ceramic proppant and pore size,optimizing the particle size distribution of bridging agents,doing performance evaluation experiments and optimizating treatment of well killing fluid to manufacture reservoir protection,temporary plugging and layer transfer killing fluid.At last,research and design killing scheme with the new killing fluid combining with killing technology.Choosing high acid soluble temporary plugging agent through the fine calculating the size of the temporary plugging fracture,matching the size of the temporary plugging particles and proportion.Through the temporary plugging agent added amount experiment eventually determined to be 20%,formed two sets of temporary plugging pressure well liquid formula:?1?kill fluid+15.7%180 mesh CaCO₃+4.3%320 mesh CaCO₃;?2?kill fluid+18%120 mesh CaCO₃+2%200 mesh CaCO₃.Analyses the damage time and pressure on the influence of the permeability recovery rate.Experimental results show that the drilling fluid plugging effect is good,flowbacking pressure is 1.5 MPa,flowback acid defuse plugging rate can reach 97%,and compatibility of drilling fluid temporary plugging agent is good.For treatment of well killing fluid optimization experiment was carried out,the result show that the tackifier,fluid loss agent,clay stabilizing agent,reduceing surfactant tension,the corrosion,pH regulator effect is good,A set of protection of temporary plugging reservoir type killing liquid has performed very well.Combining the application of well killing fluid technology,for each block horizon of well killing methods were analyzed,and the kill liquid solution application in turn new or old well layer was analyzed,for the temporary plugging type field application scheme of well kill fluid.Field experiment results show that the well chosen to protect the origin type of temporary plugging kill liquid layer has obvious effect.