Petroleum department 3rd stage

Group (A)

Drilling Lab

7th Experiment:Mud Filtration

Date of experiment: February 25th 2016

Supervised by:Mr. Pshtiwan Jaf &

Eng. Muhammad Jamal

Prepared by:Muhammad Faisal

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Aim of experiment:The aim of this experiment is to illustrate the mud

filtration during static mud condition.

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Theory: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 and the amount of filter cake that will be deposited on the wall of the well bore wherever filtration occurs. From a drilling viewpoint 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. (Azar & Robelloa, 2007)

The flow of mud filtrate through a mud cake is described by Darcy’s law. Thus, the rate of filtration is given by:

Combining with the continuity equation gives:

Vf - the volume of the filtrate, cm3 ; t – time, s ; k – permeability of the mudcake, DarcyA – the area of the filter paper, cm2 ; Dp – the pressure drop across the mudcake, atm. According to API standard, Dp = 100 psigm – the viscosity of the mud filtrate, cp ; hmc – the thickness of the filter cakefsm, fsc – the volume fraction of solids in the mud and the volume fraction of solids in the cakeThe standard API filter press has A = 45 cm2; operated at a DP = 100 psig (6.8 atm).The filtrate volume collected in a 30-min time period is reported as the standard water loss. (Lyons, et al., 2015)

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Introduction:A test to measure static filtration behavior of water

mud at ambient (room) temperature and 100-psi differential pressure, usually performed according to specifications set by API, using a static filter press. The filter medium is filter paper with 7.1 sq. in. filtering area. A half-size cell is sometimes used, in which case the filtrate volume is doubled. 

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Other Apparatus & materials:

 

Mud balance Electronic balance Beaker

Syringe Electric mixer & steel

vessels

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Water Barite Bentonite Procedures:1. Loosen the T-screw until the filter cell can be removed from the frame. 2. Remove the filter cell and disassemble it. 3. Assure that all parts of the filter cell are dry and clean. 4. Check to see that the rubber gasket in the base cap is evenly placed. 5. Check the filtrate tube in the base cap to be certain it is free of obstruction. 6. Place the screen in the base cap with the wide rim up. 7. Place filter paper on the top of the screen. 8. Place the second rubber gasket on top of the filter paper. 9. Replace the cell body. 10. Turn the cell body clockwise until it securely fastens into the J slots. 11. Check to see that the rubber gasket is evenly fitted into the top cap. 12. Fill the filter cell within the drilling mud sample. 13. Check to see that the hole in the top cap is free of obstruction.

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14. Place the top cap on the filter cell. 15. Place the cell body into the frame. 16. Tighten the T-screw securely. 17. Place a graduated cylinder under the filtrate tube and adjust the support to keep the cylinder under the filtrate tube. 18. Close the pressure-relief valve until the pressure is 100 ± 5 psi. Start timing immediately. 19. Allow the test to continue for 30 minutes. 20. Read and make note of the amount of filtrate in the graduated cylinder to the nearest 0.1 cc. 21. Open the valve on the regulator by turning counterclockwise.22. Wait until all pressure is released.23. Remove the cell from the frame by loosening the T-screw.24. Remove the top cap and pour the mud out.25. Remove the bottom cap from the cell.26. Turn the bottom cap upside down on a solid surface and remove the filter paper.27. Measure the thickness of the filter cake to the nearest 1/32 inch.

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Calculation:

Mud cake thickness=3mmVolume of mud filtrate=25ml

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Discussion:Q1) why the rubber gaskets are necessary?A1) to prevent any leakage.Q2) why is the screen used for this test?A2) the screen is used beneath the filter paper to distribute the pressure evenly on the paper and prevent the rupture of the paper.Q3) in real wellbore condition, what forms the mud cake?A3) in wellbore condition the mud cake is formed of the rock cuttings mainly in permeable zones and the mud filtrates into the walls of the wellbore.

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Q4) what are the advantages of the mud cake?A4) the mud cake stops the loss of drilling fluids and can be a sign to identify porous and permeable zones.

ReferencesAzar, J. & Robelloa, S., 2007. Drilling Engineering. s.l.:PennWell Books.

Lyons, W., Plisga, G. J. & Lorenz, M., 2015. Standard Handbook of Petroleum and Natural Gas Engineering. New York: Gulf Professional Publishing.

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