Patent ID: 7980329

Claim:
A system for drilling a wellbore comprising: a wellbore; a variable density drilling mud disposed in the wellbore, wherein the variable density drilling mud comprises compressible particles and drilling fluid; drilling pipe disposed within the wellbore; a bottom hole assembly coupled to the drilling pipe and disposed within the wellbore; and a drilling mud processing unit in fluid communication with the wellbore, wherein the drilling mud processing unit is configured to separate the compressible particles from the variable density drilling mud; and wherein the drilling mud processing unit comprises: a rig shaker screen configured to receive the variable density drilling mud and cuttings from the wellbore and to divert material to a shaker flow path; a cutting shaker screen coupled to the rig shaker screen and configured to receive the material from the shaker flow path and to divert material from the shaker flow path to a cutting flow path; one of a hydrocyclone, a settling tank, and a centrifuge coupled to the cutting shaker screen and configured to receive material from the cutting flow path, separate material in the cutting flow path based on density, and provide material having a density similar to the compressible particles to an additional shaker screen; and the additional shaker screen configured to remove the compressible particles from the material having a density similar to the compressible particles.