Study and Application of a Method for Evaluating the Performance of Barite Recycling

A shale gas well was drilled with high density invert emulsion drilling fluid in the third interval, and the barite recycling system was the key solids control equipment for the maintenance of drilling fluid properties. In the field operation there was no method for evaluating the performance of barite recycling system, and the barite recycling equipment was run at low efficiency. The barite recycling system was composed of a medium speed centrifuge and a high speed centrifuge. High density solids and low-density solids can be fractionally separated inside the centrifuge by different forces acted on them. The criteria for evaluating the performance of a two-speed centrifuge system are as follows:for medium speed centrifuge, the efficiency of separating the low-density solids in the underflow and the low-density solids in the overflow should be as low as possible. For high speed centrifuge, the efficiency of separating the low-density solids in the underflow and the low-density solids in the overflow should be as high as possible. A mathematical model and an evaluation method were established and tested in horizontal drilling of the well Wei204H7-6, where the medium speed centrifuge was running at a speed of 2,200 r/min, and 3.2% low-density solids were separated out of the underflow of the drilling fluid. On the other hand, 20.74% low-density solids were separated out of the overflow of the drilling fluid, apparently not being up to the evaluation criteria. Then the speed of the medium-speed centrifuge was reduced to 2,000 r/min, at which only 0.15% low-density solids were separated out from the underflow, and 4.6% low-density solids were separated out from the overflow, satisfying the criteria to some extent. The high speed centrifuge was run at 2,805 r/min, and the efficiency at which the low-density solids were separated was 61%, realizing high efficiency operation of the centrifuge system.