Patent ID: 7762357
Filing Date: 2010-07-27
Classification: E21B

Abstract:
1. A system in well drilling operations for controlling the density of a drilling fluid in a wellbore extending into the earth from a top end adjacent the surface, said system comprising: (a) a first tubular member having a top end and a bottom end, the top end of said first tubular member extending adjacent to or above the top end of the wellbore, the bottom end of said first tubular member being located in the wellbore, said first tubular member having a predetermined outer diameter; (b) a second tubular member having a top end and a bottom end, the top end of said second tubular member being located adjacent to or above the top end of the wellbore and the bottom end of said second tubular member being located in the wellbore, said second tubular member having a predetermined inner diameter which is greater than the outer diameter of the first tubular member, said second tubular member being arranged such that the first tubular member is disposed within at least a portion of the second tubular member to define an annular space between the outer diameter of the first tubular member and the inner diameter of the second tubular member; (c) a drilling device connected to the bottom end of the first tubular member; (d) a drilling fluid having a predetermined density disposed in said first tubular member, wherein said drilling fluid comprises a weighting agent; (e) a base fluid having a predetermined density different than the predetermined density of the drilling fluid; (f) a combination fluid comprised of the base fluid and the drilling fluid; and (g) a centrifuge, said centrifuge having a longitudinal axis with a helical conveyor disposed along said axis, an adjustable weir plate disposed around said axis, a first fluid outlet; and a second fluid outlet; wherein the weir plate and conveyor are disposed to direct a substantial portion of said weighting agent and a portion of said combination fluid together through one of said fluid outlets.