Method and apparatus for strengthening a wellbore

摘要

Embodiments include drilling through a formation using a drill bit conveyed by a tubular string having an outer diameter at least 70 percent of the wellbore being drilled. The formation is drilled at a first rate of penetration (ROP) while pumping drilling fluid at a first flow rate. After drilling through the formation, the ROP is reduced to a second ROP, the flow rate is reduced to a second flow rate, and pressure is increased in the wellbore until drilling fluid begins to leak into the formation. While maintaining the increased pressure in the wellbore, the volume of drilling fluid lost to the formation is monitored until the rate at which the drilling fluid loss occurs is reduced. Components of this procedure are repeated until a selected wellbore strength is achieved.

主权项

1. A method of strengthening a wellbore, comprising:
drilling through a formation using a drill bit conveyed by a tubular string having an outer diameter at least 70 percent of the wellbore being drilled, wherein the formation is drilled at a first rate of penetration (ROP) while pumping drilling fluid at a first flow rate; after drilling through the formation so the tubular string extends beyond the formation, reducing the ROP to a second ROP, reducing the flow rate to a second flow rate, and increasing a pressure in the wellbore until drilling fluid begins to leak into the formation; while maintaining the increased pressure in the wellbore, monitoring the volume of drilling fluid lost to the formation until the rate at which the drilling fluid loss occurs is reduced; and repeating the increasing of pressure, leaking of drilling fluid into the formation, and monitoring the volume of drilling fluid lost to the formation until the rate at which the drilling fluid loss occurs is reduced until a selected wellbore strength is achieved.