Study on and Application of a Blocking Removal System for Reservoir Damage by Water Invasion in Low Pressure Gas Wells
Low pressure gas wells drilled in the gas field D in South China Sea have experienced serious formation damage by water invasion.The formation damage by water invasion was studied through laboratory experiments such as drilled cuttings swelling,core damage by water sensitivity,water block,core flooding with water invasion,as well as three dimensional CT scanning etc.With these experiments,the degree of formation damage by water invasion is understood.To deal with the formation damage by water invasion,a blocking removal fluid suitable for disposal of formation damage by water invasion encountered in offshore low pressure gas wells was developed with a selected water invasion control agent,a new compounded organic acid HWCP,a corrosion inhibitor,a water blocking removal agent and a clay inhibitor.Laboratory studies show that condensate water causes more serious water sensitive damage to cores with low permeability,while the water blocking damage by the condensate water is weak to medium.Cores taken from the reservoirs are easy to damage by water invasion;when displacing at 0.5 MPa for 180 min,two pieces of cores,one saturated with formation water and another with condensate water,have water invasion damage of 59.76%and 69.67%,respectively.The blocking removal fluid has low surface tension,good swelling inhibitive capacity,good corrosion inhibitive capacity and strong ability to relieve formation damage by water invasion.A natural core injected with the water invasion control agent and the blocking removal fluid has permeability recovery of 100%or higher after displacing for 180 min.The blocking removal fluid has been used on the well A9hSa drilled in the gas field D in South China Sea,and water invasion damage was successfully removed,the gas production of this well was increased from 3.3×104 m3/d to more than 9.0×104 m3/d,a good result of using the blocking removal fluid.
Low pressure gas wellWater invasion damageCompound acid blocking removal fluidWater invasion control agentField application
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