Simulation Study on the Key Parameters Affecting Pressure-Controlled Drainage Effect

Pressure-controlled drainage can effectively reduce formation pressure in a high-pressure brine layer, but the influence of some key parameters on its effect in operating process is still unclear. The characteristics of pressure-controlled drainage technology were analyzed, and its technological process was summarized. On the basis of the seepage theory of formation brine and wellbore flow theory, a mathematical model with dynamic parameters was built taking into consideration the formation pressure recovery in the shut-in period to simulate the entire process of pressure-controlled drainage. Taking Well Keshen A in Tarim Oilfield as an example, simulations were conducted and the results by simulation and measurement were analyzed. It was found that the error between them was small. The analysis of key parameters affecting the effects and cycles of water drainage showed that the shorter the shut-in time, the quicker the decline in formation pressure. When the pressure-bearing limit of throttle was raised from 5 MPa to 15 MPa, the number of times for cyclic sewage disposal could be reduced by half. However, when the formation permeability was low, the effects of the first seven operations of water drainage were remarkable, and thus the period for trial drainage was set to seven days. According to the above results, relevant improving measures were put forward to better control the key operational parameters, so as to enhance the effects of pressure-controlled drainage.