Killing fluid loss mechanism and productivity recovery in a gas condensate reservoir considering the phase behavior change

Abstract

A single well numerical model considering rock capillary pressure and hysteresis was built to study killing fluid loss mechanism and its influence on productivity recovery under different positive pressure differentials based on the gas reservoir characteristics of the gas condensate well by combining the reservoir engineering and oil and gas phase behavior theory. The results show that when reservoir pressure of near wellbore zone increases to the critical pressure of condensate oil, the three-phase (oil, gas, water) flow will change to two-phase (oil, water) flow, the gas block effect will weaken, and water-phase relative permeability will increase, which can be manifested as sharp increase of killing fluid loss rate; and the rising fluid loss into the reservoir can affect the phase of condensate oil and gas and fluid distribution in the storage space near wellbore, and consequently lead to abnormal killing fluid loss. The larger the fluid loss volume, the longer the time is needed to flow back the killing fluid after going into operation again and the lower the fluid flow back efficiency, and the longer the time need to recover stable production of condensate oil and gas will be. Using fluid loss control solution or lowering liquid-column positive pressure differential (by using low-density killing fluid) can effectively avoid abnormal fluid loss during overbalanced well workover and guarantee productivity recovery after well workover. Key words: gas condensate reservoir, phase behavior change, killing fluid, numerical simulation, loss mechanism, productivity recovery