Piping and Equipment Arrangement

Drilling fluid should be processed through the solids-removal equipment in a sequential manner. The most common problem on drilling rigs is improper fluid routing, which causes some drilling fluid to bypass the sequential arrangement of solids-removal equipment. When a substantial amount of drilling fluid bypasses a piece or pieces of solids-removal equipment, many of the drilled solids cannot be removed. Factors that contribute to inadequate fluid routing include ill-advised manifolding of centrifugal pumps for hydrocyclone or mud cleaner operations, leaking valves, improper setup and use of mud guns in the removal section, and routing of drilling fluid incorrectly through mud ditches.

Barite

Silt

Colloidal

1

|

II 1

62 50 40

20 1210 8

1905 1000 838 500

Gumbo Removal

186 143 124 101

76 70

62 50 40

Separation Particle Size: >1000 micron (discard) Primary Application: Gumbo Applications Unweighted

Mud Cleaner

Shale Shaker

Separation Particle Size: >65 micron (discard) Primary Application: All

Separation Particle Size: >55 micron (discard) Primary Application: Weighted and Closed Systems

Desander

Separation Particle Size: >40 micron (discard) Primary Application: Unweighted mi

Figure Solids Control

Figure 5.2. General solids control equipment removal capabilities.

20 1210 8

Desilter

Separation Particle Size: >20 micron (discard) Primary Application: Unweighted

Centrifuge

Separation Particle Size: >2 micron (discard) Primary Application: Unweighted/Weighted Closed Systems n

Figure 5.2. General solids control equipment removal capabilities.

Each piece of solids-control equipment should be fed with a dedicated, single-purpose pump, with no routing options. Hydrocyclones and mud cleaners have only one correct location in tank arrangements and therefore should have only one suction location. Routing errors should be corrected and equipment color-coded to eliminate alignment errors. If worry about an inoperable pump suggests manifolding, it would be cost saving to allow easy access to the pumps and have a standby pump in storage. A common and oft-heard justification for manifolding the pumps is, ''I want to manifold my pumps so that when my pump goes down, I can use the desander pump to run the desilter.'' What many drilling professionals do not realize is that improper manifolding and centrifugal-pump operation is what fails the pumps by inducing cavitation. Having a dedicated pump properly sized and set up with no opportunity for improper operation will give surprisingly long pump life as well as process the drilling fluid properly.

Suction and discharge lines on drilling rigs should be as short and straight as possible. Sizes should be such that the flow velocity within the pipe is between 5 and 10 ft/sec. Lower velocities will cause settling problems, and higher velocities may induce cavitation on the suction side or cause erosion on the discharge side where the pipe changes direction. The flow velocity may be calculated with the equation:

2.48(insided diameter in)

Pump cavitation may result from improper suction line design, such as inadequate suction line diameter, lines that are too long, or too many bends in the pipe. The suction line should have no elbows or tees within three pipe diameters of the pump section flange, and their total number should be kept to a minimum. It is important to realize that an 8-inch, 90° welded ell has the same frictional pressure loss as 55 feet of straight 8-inch pipe. So, keep the plumbing fixtures to a minimum.

0 0

Post a comment