Supervised By : Mr.Pshtewan Jaf
Aim of experiment:
The test consists of monitoring the rate, at which fluid is forced from a
filter press under specific conditions of time, temperature and pressure,
then measuring the thickness of the residue depositedupon the filter
The filtrationandwall building characteristicsof a drilling mud are important
for providing a relative measure of the amount of mud filtrate invasionintoa
porous and permeable formationand the amount of filter cake that will be
depositedonthe wall of the well bore wherever filtrationoccurs. Froma
drilling viewpoint theseproperties give anindicationof the amount of water
(or oil) wetting that can take place in filtrate sensitive formations andthe
potential for tight hole or differential sticking problems. For productive,
hydrocarbon bearing formations these propertiesgive anindicationof the
amount of filtrate invasionandpermeability damage that can be expected.
Loss of fluid (usually water and soluble chemicals) from the mud to the
formation occurs when the permeability is such that it allows fluid to pass
through the pore spaces. As fluid is lost, a build up of mud solids occurs
on the face of the wellbore. This is the filter cake.
The loss of liquid from a mud due to filtration is controlled bythe filter cake
formed of the solid constituents in the drilling fluid. Two types of filtration
occur; dynamic, while circulating and static, while the mud is at rest.
Dynamic filtration reaches a constant rate when the rate of erosionof the
filter cake due to circulating matches the rate of deposition of the filter
Static filtration will cause the cake to grow thicker with time, which
results in a decrease in loss of fluids with time.
Filtration tests are conducted under two differentconditions:
1. The standard API filtration test is conducted at surface (or room)
temperature and 700 kPA, (l00 psi), pressure for thirty minutes. For this
test the fluid loss is the volume (in millilitres) of filtrate collected in this
time period and the filter cake thickness (in millimetres) is the thickness
of the cake that is deposited on the filter paper in this time period.
2. The API high temperature, high-pressure test, (HTHP test) is
conducted forthirty minutes of filtration at a temperature of l49 C, (300
F), and a differentialof 3450 kPa, (500 psi). For this test the filtrate must
be collected under a backpressure of 700 kPA, (l00 psi) in order to
prevent vaporization of the filtrate.
Apparatus of experiment
Standard Filter Press
1. Be sure each part of the cell is clean and dry, particularly the screen,
and that the gaskets are not distorted or worn. The screenshould be
free of sharp edges,burrs or tears.
2. Assemble the cell as follows: Base Cap, rubber gasket, screen,one
sheet of filter paper, rubber gasket and cell body.
3. Pour the freshly stirred sample of fluid into the cell to within 0.5 inch
(13 millimeters) to the top in orderto minimize CO2 contamination of the
filtrate. Check the top cap to insure the rubber gasket is in place and
seated all the way around and complete the assembly. Place the cell
assemblyinto the frame and secure with the T-screw.
4. Place a clean dry graduated cylinder under the filtrate exit tube.
5. Close the relief valve and adjust the regulator so that a pressure of
100 ± 5 pounds per square inch (690 ± 35 kilopascals)is applied in 30
seconds or less.The test period begins at the time of initial
6. At the end of 30 minutes, measure the volume of filtrate collected.
Shut off the air flow through the pressure regulator and open the relief
7. Reportthe volume of filtrate collected in cubic centimeters to the
nearest 1/10th centimeter3 as the API filtrate. Reportthe time interval
and the mud temperature in °F (°C) at the start of the test. Save the
filtrate for running chemicalanalysis.
8. Check to see that all pressure has been removed from the cell, and
then remove the cell from the frame. Disassemblethe cell, discard any
remaining mud and using extreme care save the filter paper and
depositedcake with a minimum of disturbance to the cake. Wash the
filter cake on the paper with a gentle stream of water or with dieseloil if
oil mud is being tested.
9. Measure and report the thickness of the filter cake to the nearest 1/32
inch (0.8 millimeter). A cakethickness less than 2/32 inch is usually
considered acceptable.Observations as to the quality of the cake should
be noted. Notations such as hardness, softness,toughness,slickness,
rubberiness,firmness,flexibility and sponginess are appropriate
filtration on formation damage:ffectof mudE-
is an undesirable operational and economic problem that can occurs during the various
phases of oil and gas recovery from subsurface reservoirs including production, drilling,
hydraulic fracturing, and work-over operations. Formation damage assessment, control,
and remediation are among the most important issues to be resolved for efficient
exploitation of hydrocarbon reservoirs.
Deep bed filtration of fines with capture and permeability damage takes place near to
production wells, in drilling operation. The particles in drilling fluid are captured by size
exclusion (straining) or by different attachment mechanisms (electric forces, gravity
segregation and diffusion).
Mud cake occur when:-
, such as a drilling fluid, is forcedslurrymedium when apermeableThe residue deposited on a
. Filtrate is the liquid that passes through the medium,pressureagainst the medium under a
cake-rate and filterfiltrationleaving the cake on the medium. Drilling muds are tested to determine
arepermeabilityproperties. Cake properties such as cake thickness, toughness, slickness and
stuckthe cake that forms on permeable zones in the wellbore can causeimportant because
can resultproductionand other drilling problems. Reduced oil and gaspipe
ws deep filtrate invasion. A certain degree ofwhen a poor filter cake allodamagereservoirfrom
-completions in highholeopencake buildup is desirable to isolate formations from drilling fluids. In
of an external filter cake is preferable to a cake that formsformationheangle or horizontal holes, t
.formation damagepartly inside the formation. The latter has a higher potential for
likely to cause theand thick filter cake build up arefiltrationExcessive-
,due to reduced hole diameter.Tight hole, causing excessive barrier. Increased pressure
Differential sticking, due to an increased pipe contact in filter cake.
-Pressure affects filtration by:
Compressing the filter cake, reducing its permeability and therefore reducing the filtrate.
-Temperature affects on filtration by:
Reducing the viscosity of the liquid phase and hence increasing filtration.
-Time affects on filtration:
With all other factors being constant, It has been found in early work that the volume of
fluid lost is roughly proportional to the square root of the time for filtration.
-Form of mud cake and mud filtration with time cause to occur of formation damage:
Formation damage is defined as the impairment to reservoir (reduced production) caused by
wellbore fluids used during drilling/completion and workover operations. It is a zone of reduced
permeability within the vicinity of the wellbore (skin) as a result of foreign-fluid invasion into
the reservoir rock.
-Preventing formation damage:
1-Ability to recover fluids from the reservoir is affected very strongly by the hydrocarbon
permeability in the near-wellbore region
2-Although we do not have the ability to control reservoir rock properties and fluid properties,
we have some degree of control over drilling, completion, and production operations
Payatakes,A.C.etal.,“Applicationof PorousMediummodelstothe Studyof DeepBedFiltration,”
Can. J. Chem.Eng.,52, 727 (1974).
Jiao,D. and M.M. Sharma, “Mechanismof Cake BuildupinCrossflow Filtrationof Colloidal
Suspensions,”Journal of ColloidalandInterfacial Science,1994. 162:p. 454-462.
Fisk, J.V., and Jamison,D.E., "Physical Properties of Drilling Fluids atHigh Temperatures and Pressures,"SPE
Drilling Engineering,December 1989,pp.341-46.