Patent GB-1359775-A (GB)
Title: Method and apparatus for treating drilling mud
IPC: E21B21/06
Filed: 1972-08-01
Abstract: 1359775 Treating drilling mud GULF RESEARCH & DEVELOPMENT CO 1 Aug 1972 [11 Aug 1971] 35874/72 Heading B2H [Also in Division El] Ferrous-abrasive-laden drilling mud discharged from a well is treated for recirculation in an abrasive jet drilling process by screening oversize cuttings from the drilling mud, dividing the screened drilling mud into a ferrousabrasive-rich stream and a drilling mud stream substantially devoid of ferrous abrasives, cleaning the ferrous abrasives in the ferrous-abrasive-rich stream to reduce the concentration of drilling mud on the ferrous abrasive to below 5% by weight drying the clean ferrous abrasives, and mixing the dried ferrous abrasives with drilling mud liquids at a controlled rate to form a drilling mud for recirculating through the well. As shown, mud with suspended cuttings is discharged from a well 10 into a rotating ditch 16 which delivers the mud on to a shale shaker vibrating screen 18. The oversize cuttings are discarded at 20 and the mud with undersize solid particles is delivered to a magnetic separator 24 in which the ferrous abrasive particles are separated from the major portion of the drilling mud and discharged as a concentrated slurry which is pumped into a centrifugal cleaner 32 to further reduce the concentration of drilling mud on the abrasive particles. The cleaned abrasive particles are discharged from the cleaner on to a conveyor 36 which delivers the particles to a rotary kiln drier 38 from which the dried particles are discharged by an elevator 54 on to a screen 56. The oversized and undersized abrasive particles are rejected at 58 and 60 and the dried and sized abrasive particles are delivered to a storage hopper 61. The major part of the liquid delivered into cleaner 32 with non- abrasive solids and some broken abrasive particles are discharged through a line 40 and pumped by a pump 42 through a line 44 into a cyclone 46. Ferrous abrasive particles are discharged from the cyclone on to a screen 48 where they are washed by a water stream circulated by a pump 50. The washed abrasive particles are then discharged on to the conveyor 36. If only a small part of the abrasive particles are broken, the drilling mud discharged from the cleaner 32 may be returned through a line 43 to the magnetic separator 24, bleeding of the drilling mud from the system being periodically effected through a line 41 to prevent build-up of broken abrasives in the system. Another alternative is to deliver the drilling mud discharged from the cleaner to a second magnetic separator to receive the small amount of abrasives not separated in the cleaner. Dirty liquid from the magnetic separator 24 is delivered to compartment 62a of a mud pit 62. A pump 64 feeds the dirty liquid to cyclones 68, the under flow, containing cuttings and a small amount of abrasives, being discarded at 70 and the overflow containing clay particles being delivered through line 72 as "clean" liquid to compartment 62b of the mud pit. A pump 74 delivers a first portion of the clean liquid through line 78 to adjust the volume of liquid passing through line 44, a second portion through line 80 into compartment 62a to maintain a constant supply of liquid, and a third portion through line 81 back to compartment 62b. Make-up chemicals are added to line 81 from a hopper 82 to maintain the desired drilling mud properties. Clean liquid is delivered from compartment 62b by a pump 86 to a cooler 88, a portion of the cooled liquid being returned to compartment 62b and another portion to a vibrating screen 94 and thence to compartment 62c. A pump 98 withdraws clean liquid from compartment 62c and delivers it through lines 102, 104 to a blender 106 to which dried and sized abrasive particles is delivered from hopper 61 via a weigh feeder 108. A concentrated suspension of abrasive in clean liquid is delivered from the blender by a pump 110 and an injector 112 to a line 114 for delivery to the well 10 together with the major portion of the clean drilling liquid delivered through line 116 to a battery 118 of high pressure pumps connected by a line 120 to line 114.