Treatment of trap effect via pressure-controlled release

Trap pressure caused by lost circulation or injecting drilling fluids into formations brings great challenges to the formulation of on-site well controls. Pressure-controlled release is an effective technique to deal with formation trap effects during drilling. After analyzing the characteristics of trap pressure and actual drilling data, attempts were made to develop the pressure-controlled release technique for trap pressure. By strictly implementing the technical workflow of shut-in pressure calculation, pressure-controlled release, circulating blow-off and choke-manifold mud-density reduction, the trapped fluids enter the wellbore at a constant rate according to a certain proportion, and the trap pressure is gradually reduced to solve the short-term trap pressure problem of thief zones. The successful application in Well YT1, southwestern Sichuan Basin, shows that a reasonable pressure-controlled release can safely reduce the trap pressure, expand the drilling fluid density window, and seek a pressure balance between well kick and lost circulation, which is favorable for well control.