CHLORIDE DETERMINATION

•Chloride ions exist in a mud system as Salts of Sodium, Magnesium, Calcium, or Potassium.
The determination of the Chloride ion present in the mud filtrate may give an indication of a Salt water flow, or the presence of a Salt formation or stringer.
•In mud systems to which Salt has been added, the Chloride measurements show the amount of salinity present in the mud.

Test Procedure:
•Measure 1.0 ml of filtrate into a white titration dish and dilute to a convenient volume with distilled water.
•Add a few drops of Phenolphthalein indication solution. If a pink color develops, add N/50 Sulfuric Acid until the pink color completely disappears.
It is not necessary to record the volume of N/50 Sulfuric Acid added.
•Add 4-5 drops of Potassium Chromate indicator to obtain a yellow color.
•Add Silver Nitrate while swirling or stirring until the color changes from yellow to orange-red (brick red), and persists for 30 seconds. Calculations:
•If 0.0282 N Silver Nitrate is used: –mg/L Chlorides = 1000 X ml of Silver Nitrate added
•If 0.282 N Silver Nitrate is used: –mg/L Chlorides = 10000 X ml of Silver Nitrate added Remarks:
•mg/L Salt (NaCl) = 1.65 X mg/L Chlorides
•The Chloride test may be run on the same sample used in the Pf determination, if the Mf test was not performed.
•Avoid contact with the Silver Nitrate solution. Wash immediately with water if Silver Nitrate gets on the skin or clothing.
•The end point of the reaction is when the Silver Chromate is when the first detectable permanent color change from yellow to a light brick red occurs.
•When using the weak Silver Nitrate solution, the end point is approached very gradually. Therefore, the formation of the Silver Chromate can be seen by a color change for yellow to brick red.
•If the strong Silver Nitrate is used, the end point is approached much more rapidly. Hence the early formation of the Silver Chromate, and is brick red color may be missed due to the larger amounts of Silver Nitrate being added. The color change will go from yellow to red. As soon as the red color is seen, the titration is complete.
•White lumps of Silver Chloride form when titrating high concentrations of Salt. This should not be mistaken for the end point.
•A high pH will precipitate Silver Oxide.

pH DETERMINATION

•The acidity or alkalinity of a drilling mud is indicated by the Hydrogen ion concentration, which is commonly expressed in terms of pH.
A perfectly neutral solution has a pH of 7.0, whereas alkaline (basic) solutions have a pH range between 7.0-14.0, and acidic solutions have a pH less than 7.0.
•The pH measurement is used as well to indicate the presence of contaminants such as cement or anhydrite.
Test Procedure
•pHydionPaper:
–This method may be used on the mud filtrate, or whole mud directly. –Place a 25 mm (1 inch) strip of indicator paper on the surface of the mud to be tested and allow it to remain until the liquid has wet the surface and the color has stabilized.
This takes approximately 1 minute.
–Compare the color standards provided with the test paper (which was not in contact with the mud solids) to the color standards provided with the test paper, and estimate the pH of the mud accordingly.
•Color pH Strips: –This method applies onlyto the mud filtrate.
–After obtaining a sample of mud filtrate, totally immerse the colored portion of the color pH strip into the filtrate, and remove immediately.
–After a short period of color stabilization (10-15 seconds), compare the color of the wetted strip with the color standards provided in the color pH plastic container.
•An estimate may be necessary if a color does not exactly match a particular pH value.

CATION EXCHANGE CAPACITY(MBT)

The Methylene Blue Dye Test, (MBT), is used to determine the Cation Exchange Capacity of the solids present in a water base drilling mud. Only the reactive portions of the clays present are involved in the test and materials such as Barite, Carbonates, and Evaporitesdo not affect the results of the test, since these materials do not adsorb the Methylene Blue •For Bentonite based mud systems, the MBT provides an indication of the amount of reactive clays which are present in the drilling mud solids and for Bentonite free, water based mud systems, the MBT reflects the reactivity of the drilled solids. The test cannot distinguish between the type of clays but, if a reactivity for the drilled solids is known or assumed, it can be used to determine the amount of Bentonite present in the Bentonite based systems Test Procedure: •Using the completely filled, 3 ml syringe, measure 2.0 ml of mud sample to be tested into the Erlenmeyer flask containing 10-15 ml of distilled water. •Add 15 ml Hydrogen Peroxide and 1 ml of 5N Sulfuric Acid. Swirl or stir as required to mixed the solution •Boil gently for approximately 10 minutes, and dilute with 20 ml fresh water. Test Procedure: •Add Methylene Blue Dye in 1.0 ml increments. After each dilution, swirl the flask and stir vigorously for at least 20 seconds, and remove a drop of sample on the end of the stirring rod. •Apply the drop to a piece of filter paper making the drop with the amount of Methylene Blue added between each increment. The approximate end point is reached when a blue ring spreads out from the blue spot on the filter paper. •At this point, without further addition of Methylene Blue, swirl the flask an additional 2 minutes, and place another drop on the filter paper. If the blue ring is again apparent, the end point has been reached. •If the ring did not appear, continue with the Methylene Blue increments until a blue ring permanently forms after two additional minutes of swirling Note: For increased accuracy, 0.5 ml increments may be used as the end point is approached. The blue ring is more apparent on the reverse side of the filter paper from which the drop is placed Calculations: Note:Thereare 2 different strengths of Methylene Blue dye that is used todetermine the Equivalent Bentonite Content. One will have to determine which strength of dye the chemical testing company is supplying •Stronger Strength of Methylene Blue: –kg/m3Reactive Clay ( Equivalent Bentonite Content) = 14.25 X ml Methylene Blue ml of Mud Sample –lb/bbl Reactive Clay ( Equivalent Bentonite Content) = 5 X ml Methylene Blue ml of Mud Sample •Weaker Strength of Methylene Blue –kg/m3Reactive Clay ( Equivalent Bentonite Content) = 10 X ml Methylene Blue ml of Mud Sample –lb/bbl Reactive Clay ( Equivalent Bentonite Content) = 3.5 X ml Methylene Blue ml of Mud Sample

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SOLIDS CALCULATIONS

•To completely analyze a drilling fluid for the amount of solids present, the following calculations should be used.
Low Density, UnweightedMud (No Oil, No Salt)
•Procedure:
–Measure Mud Density, D (kg/m3)
–Measure Bentonite from Methylene Blue Test, MBT (kg/m3)
•Volume Fraction of Solids, Fs
•Fs = [(D /1000) –1] X 0.625
–Volume Fraction of Water, Fw
•Fw= 1 –Fs
–Total Amount of Low Gravity Solids, LGS (kg/m3)
•LGS = D –(FwX 1000)
–Amount of Drilled Solids, DS (kg/m3)
•DS = LGS –MBT
Low Density, UnweightedMud (With Oil, No Salt)
•Procedure:
–Measure mud density, D (kg/m3)
–Measure Bentonite from Methylene Blue Test, MBT (kg/m3)
–Read the volume fraction of oil from the retort, Fo
•Volume Fraction of Solids, Fs
–Fs = [(D / 1000 –1) + (0.2 X Fo)] X 0.625
•Volume Fraction of Water, Fw
–Fw= 1 –(Fs + Fo)
–Total Amount of Low Gravity Solids, LGS (kg/m3)
•LGS = D –[(FoX 800) + (FwX 1000)]
–Amount of Drilled Solids, DS (kg/m3)
•DS = LGS –MBT
Low Density, UnweightedMud (With Oil, No Salt)
•Note: The oil fraction is obtained from the retort. The volume fraction of solids is obtained from the formula. This is done because small errors in reporting the volume fraction of solids can occur when taken from a retort in a unweightedlow density mud.
Low Density, UnweightedMud (With Salt, No Oil)
Note: These calculations should be used for fluids containing chlorides over 10,000 mg/L.
•Procedure:
–Measure Mud Density, D(kg/m3)
–Measure chloride content, Cl(mg/L)
–Measure Bentonite form Methylene Blue Test, MBT(kg/m3)
–Read the volume fraction of water from retort, Fw
–Read the volume fraction of Oil from retort, Fo
–Read the volume fraction of Salt in the mud from Figure 1.1, F Salt
Low Density, UnweightedMud (With Salt, No Oil)
–Amount of Salt in Mud, S(kg/m3)
•S = [(1.65 X Cl) X (Fw+ Fsalt)] / 1000
–Amount of Low Gravity Solids, LGS(kg/m3)
•LGS = 1.625 {D –[1000 (1 –Fsalt) ] + (160 X Fo) } –(0.375 X S)
–Amount of Drilled Solids, DS(kg/m3)
•LGS = LGS–MBT
–True Volume Fraction of Water, True Fw
•True Fw= [1.625 (1 –Fsalt)] –[(D + S) / 1600]
–Volume Fraction of Solids, Fs
•Fs = 1 –True Fw

Low Density, UnweightedMud (With Salt, With Oil)
Note: These calculations should be used for fluids containing chlorides over 10,000 mg/L.
•Procedure:
–Measure Mud Density, D(kg/m3)
–Measure Chloride content, Cl(mg/L)
–Measure Bentonite form Methylene Blue Test, MBT(kg/m3)
–Read the volume fraction of water from retort, Fw
–Read the volume fraction of Oil from retort, Fo
–Read the volume fraction of Salt in the mud from Figure 1.1, Fsalt

Low Density, UnweightedMud (With Salt, With Oil)
–Amount of Salt in Mud, S(kg/m3)
•S = [(.65 X Cl) X (Fw+ Fsalt)] / 1000
–Amount of Low Gravity Solids, LGS(kg/m3)
•LGS = 1.625 {D –[1000 (1 –Fsalt) ] + (160 X Fo) } –(0.375 X S)
–Amount of Drilled Solids, DS(kg/m3)
•LGS = LGS–MBT
–True Volume Fraction of Water, True Fw
•True Fw= [1.625 (1 –Fsalt)] –[(D + S) / 1600]
–Volume Fraction of Solids, Fs
•Fs = 1 –(True Fw+ Fo)
Weighted Systems
•Procedure:
–Measure the mud density, D(kg/m3)
–Measure the Chlorides, Cl(mg/L)
–Measure the Bentonite from Methylene Blue Test, MBT(kg/m3)
–Read the volume fraction of water from the retort, Fw
–Read the volume fraction of oil from the retort, Fo
–Read the volume fraction of Salt in the mud from Figure 1.1, F Salt
–Determine the volume fraction of solids from the retort, Fs
Weighted Systems
–Amount of Salt in mud, S (kg/m3)
•S = (1.65 X Cl) (Fw+ F Salt)/1000
–Amount of Total UndissolvedSolids, TS (kg/m3)
•TS = D –[(FoX 800) –(FwX 1000)] –S
–Average Relative Density of UndissolvedSolids, Dr
•Dr = TS / (Fs –F Salt) X 1000
–Amount of Barite in Mud, BAR (kg/m3)
•BAR = TS X [2.62 –(6.82/Dr)]
–Amount of Low Density Solids, LDS (kg/m3)
•LDS = TS –BAR
–Amount of Drilled Solids, DS (kg/m3)
•DS = LDS –MBT



Salt Volumes graph

RETORT / SOLIDS ANALYSIS

The retort apparatus is used to determine the amount and type of solids and liquids present in a drilling mud sample. Mud is placed in the steel container and then heated until the liquid portion is vaporized.

The vapor is passed through a condenser in which it is cooled, and then collected in a graduated cylinder.
•The volume of the water and oil is measured as a fraction of the total mud volume.
•For accurate results, a true mud density should be used for calculations, an accurate air free sample must be used, and a volume correction factor should be determined for oil content if it is present in the mud. Test Procedure
•Lift the retort assembly from the insulator block. Using a spatula as a screwdriver, remove the sample cup from the retort chamber.
•Pack the upper chamber with fine steel wool, or add 5-6 drops of “liquid steel wool”to the mud in the sample cup. Test Procedure
•Fill the lower sample cup with a freshly stirred mud sample, and replace the calibration lid, allowing any excess to escape.
•Wipe off any excess mud and screw the lower sample cup (with calibration lid still in place) into the upper chamber, maintaining both upper and lower chambers in the upright position. Screw condenser onto the outlet hose of the upper chamber Test Procedure
•Replace the retort assembly in the insulator block, and close the insulating cover.
•Add a drop of wetting agent (Aerosol) to a 10 cm3or 50 cm3graduated cylinder (depending on the size of retort being used), and place it under the drain of the condenser.
Plug in the retort and turn it on. Continue heating until liquid no linger drips from the condenser.
When using a thermostat retort, the light will go out at the end of the test Solids Calculations
•Most retorts are only accurate to within 1.0-2.0%. For that reason, most low solids muds, i.e.: muds with low mud densities that contain no Barite, salt or oil, use the following formula to calculate the volume fraction of solids:
•Volume Fraction of Solids (% Solids) = [(Mud Weight (kg/m3) / 1000) –1] X 0.625 Solids Calculations
•If a Baroid Retort is used, read the volume of oil and water. Calculate the fractions as follows if a 10 cm3retort is used:
•Fo(volume fraction of oil) = cm3oil / 10
•Fw(volume fraction of water) = cm3of water / 10
•Fs (volume fraction of solids) = 1.00 –total liquid fraction

SAND CONTENT

The API sand content is defined to be that portion of the drilling mud solids whose size is greater than 74 microns. The test can be used to give a qualitative, relative indication of the solids removal equipment effectiveness, the relative amount of coarse Barite present, and the abrasiveness of the mud.
Equipment:
•The sand content set consists of a 63.5 mm, 74 micron (200 mesh) sieve, a small funnel to fit snugly over the sieve, and a conical glass tube graduated in percent, and having two fluid level indicator lines





Test Procedure
•Fill the glass measuring tube to the indicated mark with the mud to be tested. Add water to the next mark. Close the mouth of the tube and shake vigorously.
•Pour the mixture onto the screen tapping it lightly to aid passing of the diluted mud through the screen. Add more clean water, and repeat this wet screening procedure until the wash water in the tube is clear. Wash the sand retained on the screen to free it of any remaining mud

Test Procedure
•With the sieve in an upright position, fit the funnel over the sieve. Invert slowly and fit the funnel tip into the mouth of the cleaned measuring tube.
•Back wash the sand from the sieve using a fine spray of clean water with the measuring tube positioned vertically upright, allowing the sand to settle in the tube for a few minutes.
•Report the sand content as the volume fraction of sand, (the volume percent divided by 100).
•For example, if the sand content is read as ¼%, the volume fraction is reported as 0.0025%

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Filtration Tests

•The filtration and wall building characteristics of a drilling mud are important for providing :
–a relative measure of the amount of mud filtrate invasion into a porous and permeable formation,
–the amount of filter cake that will be deposited on the wall of the wellbore wherever filtration occurs.
–From a drilling view point, these properties give an indication of the amount of water (or oil) wetting that can take place in filtrate sensitive formations,
–and the potential for tight hole or differential sticking problems. For productive, hydrocarbon bearing formations,
–these properties give an indication of the amount of filtrate invasion and permeability damage that can be expected.
•Filtration tests are conducted under two different conditions –standard API filtration test •surface (or room) temperature
–The API High Temperature
–High Pressure test (HT-HP test)
•±150 degrees Celsius (300 degrees F) or bottom hole temperature Standard API Test Procedure:
•Pour the mud sample into the cell, secure the lid and make sure all valves are in the correct positions to permit the application of pressure to the sample to be filtered.
If necessary, place a fresh CO2cartridge in the holding cylinder and screw the cylinder on quickly and securely to puncture the cartridge . Standard API Test Procedure:
•Place an appropriately sized, granulated cylinder under the filtration tube.
•Using the pressure gauge as an indicator, apply 700 kPa(100 psi) pressure to the sample and begin timing the test. Standard API Test Procedure:
•Collect the filtrate in the graduated cylinder for 30 minutes. At this time, remove the graduated cylinder, turn off and relieve the pressure on the test sample.
Standard API Test Procedure:
•Report the volume of collected fluid as the fluid loss in millimeters, making sure the volume is doubled if a “half area”filter press is used. •Disassemble the test cell, discard the mud, and use extreme care to save the filter paper with minimal disturbance to the filter cake. Remove excess mud from the filter cake by light washing, or lightly sliding a finger across the filter cake. Standard API Test Procedure: •Measure the thickness of the filter cake and report in millimeters.
If desirable, the filter cake texture may also be noted as being dry to slick, and mushy to firm to provide an indication of its friction factor and compressibility.
•Wash all components thoroughly fresh water, and wipe dry with a clean cloth or paper towel High Temperature
–High Pressure Filtration Test
•The following is the standard procedure adopted by the API for testing at ±149 degrees C (300 degrees F), and 3450 kPa(500 psi) differential pressure.
•Connect the heating jacket to the correct voltage, place a thermometer in the well of the jacket, and preheat the jacket to 155 deg.
C (311 degrees F). Adjust the thermostat in order to maintain a constant temperature High Temperature
–High Pressure Filtration Test
•Take warm mud from the flowline, and preheat to 50-55 deg.
C (120 –130 degrees F) while stirring.
•Load the cell as recommended by the manufacturer.
Care should be exercised not to fill the cell closer that 15 mm from the top to allow for expansion.
High Temperature
–High Pressure Filtration Test
•Place the cell in the heating jacket with both the top and bottom valves closed.
Transfer the thermometer from the heating jacket to the well of the test cell.
•Place the pressure assembly on the top valve stem and lock into place. Place the bottom pressure receiver and lock into place.
Apply 700 kPa(100 psi) to both pressure units with the valves closed. Open the top valve, and apply 700 kPa(100 psi) while heating.
•When the temperature reached ±149 deg.c (300 deg. F), open the bottom valve and increase the pressure on the top assembly to 4150 kPa( .High Temperature
–High Pressure Filtration Test •When the temperature reached ±149 deg. C (300 deg. F), open the bottom valve and increase the pressure on the top assembly to 4150 kPa( 600 psi) to start filtration.
Collect the filtrate for 30 minutes, maintaining 149 deg.
C (300 deg F) temperature, ±2 deg. C.
•If desired, record the volume after 2 seconds.
If the back pressure rises above 700 kPa(100 psi) during the test, cautiously bleed off pressure by collecting a portion of the filtrate. Record the total volume.
.High Temperature
–High Pressure Filtration Test
•The filtrate volume should be corrected to a filter area of 4581 mm2. Double the filtrate volume and report.
•At the end of the test, close both valves.
Back the T-handle screw off the regulator, and bleed of the pressure from both regulators.
•Caution:
The filtration cell will still contain ±3500 kPa(500 psi) pressure.
Maintain the cell in a upright position and cool to room temperature. After the cell is cool, continue to hole the cell upright (cap down), and loosen the top valve to bleed off the pressure slowly. High Temperature –High Pressure Filtration Test
•After the cell has cooled and the pressure has been bled off, the cell may be inverted to loose the cap screws with an Allen wrench.
Remove the cap with a gentle rocking motion.

Carefully retain the filter cake for analysis and thoroughly clean and dry all components.
•Do not use the filtrate for chemical analysis.
High Temperature
–High Pressure Filtration Test
•If filter cake compressibility is desired, the test can be repeated using 1400 kPa(200 psi) on the top pressure unit, and 700 kPa(100 psi) for the bottom pressure unit.
•Record both temperature and pressure with the results of the filtration test at all times.
The temperature of 149 deg. C (300 deg. F) is normally selected, so as to be within the range where high temperature mud treating procedures and chemicals are required.
High Temperature –High Pressure Filtration Test Note: At any time when utilizing any HT-HP filter press, if the CO2pressure runs out in the middle of the test and a replacement cartridge has to used, remember to shut the top and bottom valves prior to replacing the CO2cartridge.
Remember the filtration cell will still contain 500 psi pressure

Drilling Fluid Rheology

What is Rheology?
“Rheology is the study of deformation and flow







•Rheological properties are very important in drilling fluids
•By making certain measurements on a drilling fluid it is possible to determine how that fluid will flow under a variety of conditions, including temperature, pressure and shear rate.
Rheological measurements.
•In the field, a rotational viscometer having an industry standardized bob and sleeve is used


.
•Shear stress, viscosity, or gel strength is determined from the degree of rotation of the bob under the influence of the shear rate created in the mud by the action of the outer, rotating sleeve.
.•Because most drilling muds are non-Newtonian in behavior (pseudoplasticand thixotropic), stress, viscosity and gel strength measurements must be performed at prescribed shear rates (rotational speeds).
•The industry standard rotational speeds are 600 and 300 rpm for any steady state of rheological parameter and 3 rpm for gel strength (an indication of thixotropy) measurements.
Procedures for rheological measurements.
•Place a recently agitated sample in a suitable container and lower the instrument head until the sleeve is immersed in the drilling mud sample exactly at the scribed line of the sleeve.
•With the instrument set at 600 rpm, rotate the sleeve until a steady dial reading is obtained, (for highly thixotropic muds, this may take some time).
•The 600 rpm dial reading is taken at the point for which the change in dial reading is less than 1 degree (one dial division over a stirring time of one minute).
•When the dial reading has reached this steady value, record this as the 600 rpm dial reading, D600.
•Lower the speed to 300 rpm, and stir the sample at this speed until a steady reading is obtained using the same criteria for the steady state point. Record this value at the 300 rpm dial reading, D300.
Calculations:Apparent viscosity (cP) = D6002Plastic viscosity (cP) = D600–D300Yield point (pa) = D300-PV2Yield point (lb/ft2) = D300-PV

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