SOLID & LIQUID CONTENT AND EMULSION CHARACTERISTICS OF DRILLING FLUID

SAND CONTENT DETERMINATION:

Theory

Periodic sand content determination of drilling mud is desirable, because excessive sand may result in the deposition of a thick filter cake on the wall of the hole, or may settle in the hole about the tools when circulation is stopped, thus interfering with successful operation of drilling tools or setting of casting. High sand content also may cause excessive abrasion of pump parts and pipe connections.

Sand content is determined by elutriation, settling, or sieve analysis. Of the three methods, sieve analysis is preferred because of reliability of test and simplicity of equipment. The volume of sand, including void spaces between grains, is usually measured and expressed as percentage by volume of the mud.

Experiment Equipment : Baroid Sand Content Set:

The Baroid Sand Content Set consists of a 200-mesh sieve, funnel, and a glass measuring tube calibrated from 0 to 20% to read directly the percentage sand by volume.

Test Procedure

1. Pour mud into the Baroid Sand Content Tube until it fills up to the mark labeled “Mud to Here”. Then add water to the mark labeled “Water to Here”. Cover mouth of the tube with thumb and shake vigorously.
   2. Pour this mixture through the screen, being careful to wash everything out of the tube with clear water through the same screen. Wash sand retained on screen with a stream of water to remove all mud and shale particles.
   3. Fit funnel down over top of screen, invert slowly turning tip of funnel into mouth of tube, and wash sand back into tube with a fine spray of clear water on the back side of the screen. Allow the sand to settle.
   4. Observe the quantity of sand settled in the calibrated tube as the sand
   content of the mud.

result

Report the sand content of the mud in percent by volume (% by volume). Take into account coarse solids obtained on the screen.

Care of instrument

After each use, wash the screen, funnel and tube free of any dirt, and dry
thoroughly. Take special care to clean and dry the 200-mesh screen.

Remarks

1. In step 2 of the procedure, the pouring of the mud and water mixture through the screen can be facilitated by tapping the side of the screen with a spatula handle.
2. Contents retained on the screen in Step 2 of the procedure should not be mashed, stirred, or mutually forced through the screen with a finger,pencil, or the like, as this will give an erroneous reading and may pull the screen loose from the side of the container.

EMULSION TEST

Theory

Emulsion testers are used to indicate the stability and type of emulsion whether water-in-oil or oil-in-water. They are used in the evaluation of inverted emulsion drilling fluids, cements, and fracturing fluids. Time stability and resistance to electrolyte contamination of these systems can be predicted from a measurement of relative emulsion stability.

Test Equipment

Test Procedure

1. The Fann Emulsion Tester may be operated from self-contained batteries, external 12 volt DC or from 115-volt AC 50-60 cycle current. Select power source desired and set power switch accordingly (D.C. position is for either self-contained battery or for external storage battery).
2. Set meter multiplier switch at the X1 position with the voltage control knob at zero.
3. Immerse probe in well-stirred sample so that electrodes are covered.
4. Raise voltage slowly by turning control clockwise and watch the flag indicator below meter. When movement of the red flag occurs, indicating current flow between electrodes, read breakdown voltage on meter. If breakdown does not occur, set range switch to X2 or to X4 position and repeat above steps.
5. Clean probe carefully after each use, using care not to alter the spacing of electrode.
6. When internal batteries are depleted (indicated by a marked fall-off in output voltage as shown on the meter) remove panel from carrying case and replace the 8 No. 2 flashlight cells. Only leak-proof batteries should be used.

Caution

1. Do not touch bare metal of electrodes when instrument is turned on.
2. Do not short out electrodes.

OIL, WATER, SOLID & CLAY CONTENT DETERMINATION:

Theory

Knowledge of the liquid and solids content of a drilling mud is essential for good control of the mud properties. Such information will often explain poor performance of the mud and indicate whether the mud can best be conditioned by the addition of water or whether treatment with chemical thinner or the removal of the contaminant is required. Similarly, proper control of an oil emulsion mud depends upon a knowledge of the oil content.

For muds containing only water and solids, the quantity of each can be determined from the mud density and from the evaporation of a weighed sample of mud. Oil and water content can also be obtained measuring the liquid fraction. The latter method is only applicable to oil emulsion muds.

Test Equipment
The Baroid Oil and Water Retort Kit

The apparatus required to determine the oil, water and solids content of the mud is included in the Baroid Oil and Water Retort Kit (See figure below).

Test Procedure

1. Lift retort assembly, out of insulator block. Using the spatula as a screwdriver, remove the mud chamber from the retort.
2. Pack the upper chamber with very fine steel wool.
3. Fill mud chamber with mud and replace lid, allowing excess to escape. (This is a point where error is often introduced. Be sure that no air is trapped in the chamber. An accurate charge of mud is essential).
4. Wipe off excess mud and screw mud chamber into upper chamber.
5. Replace retort in insulator block and put insulation cover in place.
6. Add a drop of wetting agent to graduate and place under drain of condenser; then turn heater on.
7. Heat mud until oil stops coming over or until the pilot light goes out on thermostatically controlled units. For diesel oil this time will be about 15 minutes with the thermostated retorts and about 20 minutes in the uncontrolled units at 110 volts. Low or high voltage will cause variations in time required. Crude oils may require longer heating periods.
8. Read the volume of oil and of water. (A drop of wetting agent at this time will often improve the menisci for easier reading).
9. Where the new style thermostated retort is used faster heating can be obtained and the temperature is controlled to prevent overheating.

NOTE:

Nearly 100% recovery of refined oil will be obtained with this retort. If the mud is made up with crude oil, calibration runs should be made on mud containing a known percentage of the crude used. Recovery on some crudes may be as low as 60%. If the distillation is being carried on for more than 30 minutes, the retort should be removed occasionally in the uncontrolled units and observed for temperature. In any case, the retort should never be heated above a DULL RED HEAT. The heater will burn out is left on too long.

Care of Equipment

Before each retorting the following should be done:

• Use the spatula to scrape the dried mud from the mud chamber and lid to assure correct volume.
• Remove and replace any mud-caked steel wool.
• Clean the retort drain tube and condenser with a pipe cleaner.

THEORY AND CALCULATIONS OF SOLID CONTENT

The solid phase of a drilling mud units of two components, i.e. (i) High specific gravity solids with a specific gravity of 4.3 and (ii) Low specific gravity solids with a specific gravity of 2.5.

The total solids phase, in volume %, is found by the Baroid Oil and Water
Retort.

The information (data) from the retort test can be used to calculate the average specific gravity of solids, the % of different types of solids, and the % solids by weight in the mud, as shown below:

NOTE:

The accuracy of your calculations depends on the retort test data. These care should be taken while running the equipment to ensure good results.

CALCULATIONS