Study On Phase Characteristics And Development Law Of Condensate Gas Reservoir

Condensate gas reservoir is a complex and special gas reservoir between traditional oil reservoir and gas reservoir.Its complex phase change and retrograde condensation characteristics,brings great difficulties to efficient development in the filed.The development of condensate gas reservoirs plays an important role in the development of world gas fields.After preliminary exploration and development,a condensate gas reservoir field in Sinopec has entered the stage of stable production growth.How to maintain the increasing trend of production and develop condensate gas reservoirs reasonably and regularly is the main problem to be solved urgently at present.In this paper,the related research is carried out under the support of the project of Sinopec on phase behavior characteristics of the condensate gas reservoir.The phase characteristics of condensate gas reservoirs are clarified,which provides a basis for formulating reasonable development plans.On the basis of full investigation,this paper studies the phase characteristics and development laws of condensate gas reservoirs through the following three parts:(1)Through PVT phase testing experiments on condensate gas samples from three wells,the phase characteristics of well fluids are clarified,and the effects of development stages and formation layers on phase behavior are studied;(2)The effects of depletion rate,development model and formation permeability on oil and gas recovery efficiency were studied through depletion development simulation experiments;(3)The experimental results of physical simulation are verified by coMParing with the production dynamic data fed back in the field.The formation of the understanding and conclusions are as follows:(1)The experimental results of the phase characteristics of condensate gas show that the condensate gas reservoir belongs to a condensate gas reservoir with oilring in medium-low condensate oil.There are obvious differences in fluid sample composition,dew-point pressure and retrograde condensate volume between different development stages and different formation layers.These effects should be taken into account in subsequent research and field production.(2)Physical simulation results show that:(1)Depletion rate is the main factor affecting recovery.The slower the depletion rate is,the greater the gas recovery,and the faster the depletion rate is,the greater the condensate oil recovery;(2)Under the development mode of maintain constant pressure firstly and then depletion,the gas recovery and condensate oil recovery are the largest,followed by the pure closed depletion mode;(3)In parallel experiments,the gas recovery and condensate oil recovery of high permeability cores are higher than those of low permeability cores.The difference of condensate oil recovery and permeability has obvious influence on development effect.(3)The research of retrograde condensation injury on field shows that the occurrence of retrograde condensation will lead to three stages of gas-oil ratio rising slowly,rising rapidly and falling rapidly,which is basically consistent with physical simulation.In addition,the gas-oil ratio fluctuation will occur in both rapid and slow depletion modes,and the fluctuation period under slow failure mode is relatively longer.