Method and apparatus for treating a drilling fluid

Claim 1

A method for removing drilled solids from a drilling fluid being circulated in a well and containing drilled solids and a particulate weighting material denser and finer than at least a portion of the drilled solids, which comprises the steps of (a) passing said drilling fluid through a first vibrating screen sized to remove a portion of the drilled solids contained in said drilling fluid and to pass said weighting material; (b) centrifugally separating the drilling fluid passing said first vibrating screen into a low-density effluent and into an underflow slurry containing drilled solids and weighting material; (c) returning said effluent to the drilling fluid being circulated in said well; (d) screening said underflow slurry with a second vibrating screen sized to remove a portion of said drilled solids contained therein and to pass said particulate weighting material, said second vibrating screen being finer than said First vibrating screen; and (e) returning material passing said second vibrating screen to the drilling fluid being circulated in said well.

Claim 2

A method for removing drilled solids from a drilling fluid being circulated in a well and containing drilled solids and a particulate weighting material denser and finer than at least a portion of the drilled solids, which comprises the steps of (a) passing said drilling fluid through a first vibrating screen sized to remove a portion of the drilled solids contained in said drilling fluid and to pass said weighting material; (b) centrifugally separating the drilling fluid passing said first vibrating screen into a low-density effluent and into an underflow slurry containing drilled solids and weighting material; (c) returning said effluent to the drilling fluid being circulated in said well; (d) screening said underflow slurry with a second vibrating screen sized to remove a portion of said drilled solids contained therein and to pass said particulate weighting material, said second vibrating screen being finer than said First vibrating screen; and (e) returning material passing said second vibrating screen to the drilling fluid being circulated in said well.

Claim 7

A method for removing drilled solids from a drilling fluid containing barite and being circulated in a well which comprises the steps of (a) screening said drilling fluid with a first vibrating screen sized to separate a portion of the drilled solids and to pass said barite contained therein; (b) discarding said portion of drilled solids separated by said first vibrating screen; (c) centrifugally separating the drilling fluid passing said first vibrating screen into a low-density effluent and into a high-density underflow slurry containing barite and drilled solids; (d) returning said low-density effluent to the drilling fluid being circulated in said well; (e) screening said underflow slurry with a second vibrating screen sized to remove a portion of said drilled solids contained therein and to pass a major volume proportion of said barite contained therein; (f) discarding material collected on said second vibrating screen; and (g) returning material passing said second vibrating screen to the drilling fluid being circulated in said well.

Claim 8

A method for removing drilled solids from a drilling fluid containing barite and being circulated in a well which comprises the steps of (a) screening said drilling fluid with a first vibrating screen sized to separate a portion of the drilled solids and to pass said barite contained therein; (b) discarding said portion of drilled solids separated by said first vibrating screen; (c) centrifugally separating the drilling fluid passing said first vibrating screen into a low-density effluent and into a high-density underflow slurry containing barite and drilled solids; (d) returning said low-density effluent to the drilling fluid being circulated in said well; (e) screening said underflow slurry with a second vibrating screen sized to remove a portion of said drilled solids contained therein and to pass a major volume proportion of said barite contained therein; (f) discarding material collected on said second vibrating screen; and (g) returning material passing said second vibrating screen to the drilling fluid being circulated in said well.

Claim 11

A method of treating a drilling fluid being circulated in a well and containing barite and drilled solids, said method comprising the steps of (a) withdrawing drilling fluid from said well; (b) screening said drilling fluid withdrawn from said well with a first vibrating screen having an opening size no smaller than about 100 mesh on the U. S. Standard Sieve Series to remove drilled solids from the drilling fluid; (c) centrifugally separating the drilling fluid passing said first vibrating screen into a low-density effluent and into a high-density underflow slurry containing barite and drilled solids; (d) returning said effluent to said drilling fluid being circulated in said well; (e) screening said underflow slurry with a second vibrating screen having an opening size substantially smaller than that of said first vibrating screen to remove additional drilled solids from the underflow slurry, but sufficiently large to pass a major volume proportion of said barite contained in said underflow slurry; and (f) returning material passing said second vibrating screen to said drilling fluid being circulated in said well.

Claim 12

A method of treating a drilling fluid being circulated in a well and containing barite and drilled solids, said method comprising the steps of (a) withdrawing drilling fluid from said well; (b) screening said drilling fluid withdrawn from said well with a first vibrating screen having an opening size no smaller than about 100 mesh on the U. S. Standard Sieve Series to remove drilled solids from the drilling fluid; (c) centrifugally separating the drilling fluid passing said first vibrating screen into a low-density effluent and into a high-density underflow slurry containing barite and drilled solids; (d) returning said effluent to said drilling fluid being circulated in said well; (e) screening said underflow slurry with a second vibrating screen having an opening size substantially smaller than that of said first vibrating screen to remove additional drilled solids from the underflow slurry, but sufficiently large to pass a major volume proportion of said barite contained in said underflow slurry; and (f) returning material passing said second vibrating screen to said drilling fluid being circulated in said well.

Claim 13

A method of treating a drilling fluid being used in well drilling operations and containing a particulate weighting material and drilled solids, the average particle size of said drilled solids being substantially larger than the average particle size of said weighting material, said method comprising the steps of (a) passing the drilling fluid through a first vibrating screen; (b) discarding material screened out on said first vibrating screen; (c) centrifugally separating the drilling fluid passing said first vibrating screen with a sufficient number of hydrocyclones to treat the drilling fluid at the fluid circulation rate, said hydrocyclones operating to separate the drilling fluid into a low-density effluent and into a high-density underflow slurry, said underflow slurry containing substantial quantities of said particulate weighting material and substantial quantities of said drilled solids; (d) returning said effluent to said drilling fluid being circulated in said well; (e) screening said underflow slurry with a second vibrating screen having an opening size substantially smaller than that of said first vibrating screen and being particularly sized to screen out a major volume proportion of said drilled solids and to pass a major volume proportion of said particulate weighting material contained in said underflow slurry; (f) discarding material screened out on said second vibrating screen; and (g) returning material passing said second vibrating screen to said drilling fluid being circulated in said well.

Claim 14

A method of treating a drilling fluid being used in well drilling operations and containing a particulate weighting material and drilled solids, the average particle size of said drilled solids being substantially larger than the average particle size of said weighting material, said method comprising the steps of (a) passing the drilling fluid through a first vibrating screen; (b) discarding material screened out on said first vibrating screen; (c) centrifugally separating the drilling fluid passing said first vibrating screen with a sufficient number of hydrocyclones to treat the drilling fluid at the fluid circulation rate, said hydrocyclones operating to separate the drilling fluid into a low-density effluent and into a high-density underflow slurry, said underflow slurry containing substantial quantities of said particulate weighting material and substantial quantities of said drilled solids; (d) returning said effluent to said drilling fluid being circulated in said well; (e) screening said underflow slurry with a second vibrating screen having an opening size substantially smaller than that of said first vibrating screen and being particularly sized to screen out a major volume proportion of said drilled solids and to pass a major volume proportion of said particulate weighting material contained in said underflow slurry; (f) discarding material screened out on said second vibrating screen; and (g) returning material passing said second vibrating screen to said drilling fluid being circulated in said well.

Claim 20

A method of removing drilled solids from a drilling fluid that is being circulated in a well and which contains a particulate weighting material having an average particle size smaller than the particle size of a portion of the drilled solids, which comprises: (a) vibrationally screening said drilling fluid in a first screening stage to a first particle size fineness to remove part of said portion of drilled solids and to pass said weighting material and the remainder of the drilled solids; (b) centrifugally separating drilling fluid screened in step (a) into a low-density effluent, which is returned to the drilling fluid being circulated in said well, and a high-density underflow slurry containing particulate weighting material and drilled solids, and (c) vibrationally screening said underflow slurry in a second screening stage to a particle size finer than drilled solids removed in the first screening stage to remove additional particles in said portion of drilled solids from said underflow slurry and to pass and return to said drilling fluid being circulated in said well a major portion of the particulate weighting material contained in said underflow slurry.

Claim 21

A method of removing drilled solids from a drilling fluid that is being circulated in a well and which contains a particulate weighting material having an average particle size smaller than the particle size of a portion of the drilled solids, which comprises: (a) vibrationally screening said drilling fluid in a first screening stage to a first particle size fineness to remove part of said portion of drilled solids and to pass said weighting material and the remainder of the drilled solids; (b) centrifugally separating drilling fluid screened in step (a) into a low-density effluent, which is returned to the drilling fluid being circulated in said well, and a high-density underflow slurry containing particulate weighting material and drilled solids, and (c) vibrationally screening said underflow slurry in a second screening stage to a particle size finer than drilled solids removed in the first screening stage to remove additional particles in said portion of drilled solids from said underflow slurry and to pass and return to said drilling fluid being circulated in said well a major portion of the particulate weighting material contained in said underflow slurry.

Claim 24

A method of removing drilled solids from a drilling fluid that is being circulated in a well and which contains a particulate weighting material having an average particle size smaller than the particle size of the drilled solids to be removed, which comprises: (a) vibrationally screening said drilling fluid in a first screening stage to remove large size drilled solids and to pass drilling fluid containing substantially all of said particulate weighting material and the remainder of said drilled solids; (b) centrifugally separating fluid passing said first screening stage into a low-density effluent, which is returned to the drilling fluid being circulated in said well, and a high-density underflow slurry containing particulate weighting material and drilled solids finer than the drilled solids removed in said first screening stage but coarser, at least in part, than the average particle size of said particulate weighting material contained in said underflow slurry; and (c) vibrationally screening said underflow slurry in a second screening stage finer than said first screening stage to remove additional drilled solids from said underflow slurry and to pass and return to said drilling fluid a major portion of the particulate weighting material contained in said underflow slurry.

Claim 25

A method of removing drilled solids from a drilling fluid that is being circulated in a well and which contains a particulate weighting material having an average particle size smaller than the particle size of the drilled solids to be removed, which comprises: (a) vibrationally screening said drilling fluid in a first screening stage to remove large size drilled solids and to pass drilling fluid containing substantially all of said particulate weighting material and the remainder of said drilled solids; (b) centrifugally separating fluid passing said first screening stage into a low-density effluent, which is returned to the drilling fluid being circulated in said well, and a high-density underflow slurry containing particulate weighting material and drilled solids finer than the drilled solids removed in said first screening stage but coarser, at least in part, than the average particle size of said particulate weighting material contained in said underflow slurry; and (c) vibrationally screening said underflow slurry in a second screening stage finer than said first screening stage to remove additional drilled solids from said underflow slurry and to pass and return to said drilling fluid a major portion of the particulate weighting material contained in said underflow slurry.

Claim 28

A method of treating a drilling fluid that is being circulated in a well and which contains drilled solids and particulate weighting material which comrises: (a) vibrationally screening substantially the entire stream of the drilling fluid discharging from said well to remove drilled solids substantially larger than said weighting material from said drilling fluid, (b) centrifugally separating substantially all of said drilling fluid screened in step (a) into a major fraction component comprising a low density effluent, which is returned to the drilling fluid being circulated in said well, and a minor fraction component comprising a high density underflow slurry containing particulate weighting material and drilled solids; and (c) vibrationally screening said underflow slurry to remove additional drilled solids from the underflow slurry which are finer than the drilled solids removed in step (a) but coarser than a major portion of the particulate weighting material contained in the underflow slurry, and to pass and return said major portion of the particulate weighting material to the drilling fluid being circulated in said well.

Claim 29

A method of treating a drilling fluid that is being circulated in a well and which contains drilled solids and particulate weighting material which comrises: (a) vibrationally screening substantially the entire stream of the drilling fluid discharging from said well to remove drilled solids substantially larger than said weighting material from said drilling fluid, (b) centrifugally separating substantially all of said drilling fluid screened in step (a) into a major fraction component comprising a low density effluent, which is returned to the drilling fluid being circulated in said well, and a minor fraction component comprising a high density underflow slurry containing particulate weighting material and drilled solids; and (c) vibrationally screening said underflow slurry to remove additional drilled solids from the underflow slurry which are finer than the drilled solids removed in step (a) but coarser than a major portion of the particulate weighting material contained in the underflow slurry, and to pass and return said major portion of the particulate weighting material to the drilling fluid being circulated in said well.