Patent ID: 8076269
Filing Date: 2011-12-13
Classification: B29C,C09K,E21B,Y10T

Abstract:
1. A method associated with drilling a wellbore comprising: determining a pore pressure gradient and a fracture pressure gradient at a selected depth within the wellbore, selecting reusable compressible objects having a shell that encloses an interior region, wherein the compressible objects have an internal pressure at atmospheric external pressure that is in between the pore pressure gradient and fracture pressure gradient at the selected depth and greater than 250 psi, wherein the shell is configured to experience less strain when the external pressure is about equal to the internal pressure than when the external pressure is both above and below the internal pressure of the compressible object, the reusable compressible objects comprising selecting a drilling fluid; introducing the compressible objects to the drilling fluid to form a variable density drilling mud, wherein the density of the variable density drilling mud varies in a non-linear fashion along at least a portion of the wellbore and the variable density drilling mud provides a density between a pore pressure gradient and a fracture pressure gradient for at least one interval as the variable density drilling mud circulates toward the surface of a well; and drilling the wellbore using the variable density drilling mud.