Research and Application of a New Method for Dynamic Diagnosis of Gas-Cap Reservoirs
During the development of gas-cap reservoirs,crude oil,dissolved gas,gas-cap gas,condensate oil,and formation water may be produced simultaneously.Accurately calculating formation pressure and recovery percent of each phase is crucial for dynamic diagnosis and potential tapping of remaining oil and gas in such reservoirs.Current methods for calculating formation pressure fail to take water inva-sion into consideration,leading to uncertainty in production splitting,which increases the risks in subsequent adjustment and potential tap-ping.Through water influx fitting and Newton iteration methods,a new method for dynamic diagnosis of gas-cap reservoirs based on water invasion characteristic analysis and average formation pressure prediction was established.The application of this method in the Y3 gas-cap reservoir in the M oilfield indicates that crude oil and condensate oil account for 89.7%and 10.3%in the produced oil,respectively,and the produced gas contains 97.9%gas-cap gas and only 2.1%dissolved gas.The recovery efficiency of gas-cap gas and condensate oil is as high as 46.6%and 31.2%,respectively,while the recovery efficiency of crude oil and dissolved gas is merely 12.1%and 1.7%,respec-tively.These results are consistent with production test results.
gas-cap reservoirdynamic diagnosiswater invasionaverage formation pressurephase partitioningremaining oil and gas po-tential tapping
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