Study On Evaluation And Demolition Of Condensate Oil Pollution In BK Dense Gas Reservoir

In the process of gas condensate reservoir’s depletion development, retrograde condensation phenomenon inevitably appears in the formation when layer pressure drops below the dew point. Retrograde condensation damage may cause condensate gas well productivity reduced heavily, especially for the low permeability condensate gas reservoir. Well evaluated retrograde damage degree and proper methods to relieve damage help to improve the recovery. Two kinds of condensate gas sample with different condensate oil contents were measured to acquire the physical properties under high temperature and pressure. Obtained two kinds of different permeability cores from the field, named BKl group and BK2group. Monitored the near and away from wellbore depletion by different experimental methods in the long cores, and compared the condensation damage degree quantitatively for the eight experiment groups in the long cores. Removing condensate oil damage experiment is conducted and optimized the most proper method to relieve damage based on the field practice.The research results show that:the damage degree of condensate oil near wellbore region is higher than that in far wellbore region under the condition of same cores and condensate fluid; the fluid with high condensate oil content has more serious damage compared with the lower condensate oil fluid under the same other conditions; the experiment in the low permeability long cores has worse damage degree than the higher permeability cores when the other conditions are the same. Since the practice and technological limitation, early depletion is considered to be a proper way to develop the BK condensate gas reservoir. Obtained the pressure when highest condensate oil appears through CVD (constant volume depletion) experiment, then the relieve condensation experiment is conducted under this pressure, which included inject0.1HCPV (Hydrocarbon Pore Volume) dry gas,0.05HCPV dry gas and0.05HCPV carbinol,0.1HCPV nitrogen, raise temperature by15degrees Celsius and raise temperature by30degrees Celsius. The results show that the condensate gas damage has been relieved to some extent. For BK condensate gas reservoir, the method of injecting dry gas is recommended to improve condensate damage. The research results in this paper can intensify the understanding of condensate damage mechanism and relieve methods, which has some reference value for the development in similar gas reservoirs.