Determination of volume percentage of low-gravity solids in water-based drilling fluid

The %vol low-gravity solids can also be calculated from the average specific gravity (ASG) of the solids in the sample:

ASG={12MW-[%vol water][Pw] – [%vol oil][P0]}/%vol solids

%vol Low Gravity Solids=(%vol solids)(Barite SG – ASG)/(Barite SG – Low-Gravity SG)

The ASG of the solids in the drilling fluid can be determined independently with the pressurized mud balance in the same manner as the lowgravity solids and the barite. (See procedure below.)

rig-site detemination of specific gravity of drilling solids
If a laboratory balance is not available at the rig site, have a laboratory determine the volume of a pressurized mud balance and stamp the volume, in cubic centimeters, on the cup. For example, assume 240 cc:
. Collect some representative cuttings (about 100 g) from the shaker screen.
. Wash the cuttings in distilled water (or oil for an oil mud) to remove the drilling fluid.
. Place the shale cuttings in several retorts and remove the liquid from the cuttings.
. Add the dry cuttings to the cup of the pressurized mud balance and determine a mud weight.
Assume that the dry-solids weight is 9.1 ppg. To determine the weight of cuttings:
. Multiply the dry-solids weight by the cup volume and divide by 8.34 ppg/g/cc.

(9.1 ppg * 240 cc)/(8.34 ppg/g/cc) = 262 g.
To determine the volume of cuttings:
. Add water to the dry solids (stir to remove as much air as possible), pressurize the cup, and read the mud balance.
. Calculate the volume of cuttings by the equation:
Volume of Cup -{[(Mud Weight*Cup Volume)]/8.34]-Weight of Cuttings}.
Assume that the pressurized balance reads 13.7 ppg. The weight of cuttings and water in the cup can be found by dividing the weight by 8.34 ppg/g/cc and multiplying by the volume of the cup. In the example:
(13.7 ppg*240cc)/(8.34 ppg/g/cc) =394.2 g.
Since the cup contains 262 g of solids, it must contain 132 g of water:[394 g-262 g=132 g], or 132 cc of water. The cup holds 240 cc of slurry with 132 cc of water, so it contains 108 cc of cuttings:[240 cc – 132 cc = 108 cc]
The density of the cuttings may be determined by dividing the weight of the cuttings by their volume. In this example: Density=262 g/108 cc, or 2.43 g/cc.

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