Experiment 4a. API Filtration Test: API High-Pressure/High Temperature (HPHT) Filter Press.

Aim and objective of the experiment: To determine the filtration rate of mud and the spurt loss

volume of the filtrate in high pressure and temperature through a HPHT Filter Press. This helps to

optimize the effectiveness of the drilling fluid.

Results and Discussion:

The tables below show the results obtained for mud 2 and mud 3 after the API high pressure/high

temperature (HP/HT) filtration test at 200 F with a 200psi differential.

Mud 2:

Time, t (min) Sqrt(t) Filtrate Volume (cc)

1 1 4.9

4 2 9.9

7.5 2.73861278752583 13.4

9 3 15

16 4 19.25

25 5 22.75

30 5.47722557505166 26

36 5 25.75

Mud Layer thickness: 0.22 in

Spurt loss: 2.5cc

Physical Properties of the filter cake: Solid, Silky, smooth

The standard filter loss: at t=30 mins: 26 cc

Diameter of the filter paper: 2.1 inch

Area of the filter paper: 3.46 inch2

Thickness of the filter cake per

unit area of filter paper: 0.0636inch-1

Temperature: 200F

High Differential Pressure: 200psi

0 1 2 3 4 5 6 70

5

10

15

20

25

30

35

Sqrt(t) mins

Volu

me

(cc)

The graph on the above shows the effect of pressure and temperature on the rate at with the fluid is

lost through the rock surface for mud 2. Comparing the two trendlines we can see that the rate of

fluid being lost of the formation is higher in higher pressure and temperature as suppose to standard

pressure and standard temperature and pressure. This can be seen by comparing the slope of the

two trendlines

Mud 3

Time, t (mins) Sqrt(t) filtrate volume (cc)

1 1 1

4 2 4.2

7.5 2.73861278752583 6.1

9 3 6.7

16 4 9

25 5 11

30 5.47722557505166 12

36 6 13.2

Mud Layer thickness: 0.13 in

Spurt loss: 0.2cc

Physical Properties of the filter cake: very firm, flexible

The standard filter loss: at t=30 mins: 12 cc

Diameter of the filter paper: 2.1 inch

Area of the filter paper: 3.46 inch2

Fig 1: effect of high pressure and temperature on the rate of fluid lost compared to normal pressure and temperature

Thickness of the filter cake per

unit area of filter paper: 0.0376inch-1

Temperature: 200F

High Differential Pressure: 200psi

0 1 2 3 4 5 6 70

2

4

6

8

10

12

14

f(x) = 2.29575846202248 x − 0.60906351824603f(x) = 2.35398556453455 x − 0.696707720160278

HPHT Filter PressLinear (HPHT Filter Press)Normal Fitler PressLinear (Normal Fitler Press)

Axis Title

Axis Title

The graph on the left shows the effect of pressure and temperature on the rate at with the fluid is

lost through the rock surface. Comparing trend line 1 and 2 we can see that the rate of fluid being

lost of the formation is only slightly higher in higher pressure and temperature as suppose to

standard pressure and standard temperature and pressure. This can be seen by comparing the slope

of the two trend lines. Comparing the results of mud 3 with mud 2, we can see that the composition

of mud 3 mostly the polymer is preventing mud three from being lost at a higher rate in higher

temperature and pressure (200F and 200psi).

The results from this test show that the increasing temperature and pressure can have an effect on

the filtration. These effects can be minimized by using additives such as polymers as results from

mud 3 illustrates. The filtration rate from the filter cake for mud 3 was 2.35cc and 2.29cc for high

temperature/high pressure and normal temperature and pressure respectively.

One of the primary effects of increase in temperature on the drilling fluid is the decrease in fluid-

phase viscosity. This could lead to a decrease in filter cake thickness and increasing the amount of

mud filtrate going into the formation causing various hole problems and formation damage.

Fig 3: effect of high pressure and temperature on the rate of fluid lost compared to Normal pressure and temperature

Conclusion and Recommendations:

It can be concluded that the effect of Temperature and pressure has an effect on the spurt loss and

the filtration rate which can be seen from mud 2. This can be controlled by adding polymers like in

mud 3. The precision of this experiment could be improved by measuring the pH and resistivity over

a number of times. The accuracy can be improved by using different equipment inorder to decrease

the significant errors.

Experiment 4b: Determination of pH

Aim: To determine the pH of drilling mud using a pH meter.

Observation: Not much observation was made as we didn’t have the pH meter so we couldn’t carry

about the exact experiment. One of the muds when tasted had a caustic soda taste.

Results:

Mud sample pH Temperature (°C),( °F)

1 9.67 19.3, 66.74

2 9.66 19.6, 67.28

3 9.51 19.6, 67.28

pH is defined as the negative log of hydrogen ions. The above results were given to us by the lab

instructor calculated from a previous experiment. As pH for all three muds are greater than 7, they

are all alkaline. The pH value suggests that the muds have been designed to avoid corrosion of

equipment and to reduce effects of hole damage through erosion and avoid flocculation.

It is important to maintain the pH in a required range as it could cause damages to the formation or

the drill pipe. If the pH is less than 7, then it could cause corrosion on the casing, drill sting and other

bottom-hole assembly. If the pH is greater than 7, then it could cause erosion. For a pH greater then

7, the fluid is basic and this basic fluid dissolves calcite in the mud and causes the salt formation to

collapse. Special care should be provided to mud with additives in them. Mud with biological

additives such as starch with a pH value of less than 11.5 is susceptible to bacterial attack and decay.

Problem *1Calculate the amount of caustic (NAOH) required to increase the pH of the mud obtained from the experiment to 11. Molecular weight of caustic: 40Product constant of water, Kw=1.0x10-14.The required pOH is 3.So, the hydroxide ions concentration is: ¿ ¿¿

Mud Sample: pH pOH ¿14−pH

[OH-] ¿10−pOH

Mol/lChange in [ ]Mol/l

Weight required. (g/l)

1 9.67 4.33 ¿10−4.33

¿4.67E-51.0E-3-4.67E-5=9.533E-4

9.533E-4*40=0.0381

2 9.66 4.34 ¿10−4.34

¿4.57E-51.0E-3-4.57E-5=9.543E-4

9.543E-4*40=0.0382

3 9.51 4.49 ¿10−4.49

¿3.34E-51.0E-3-4.67E-5=9.67E-4

9.67E-4*40=0.0387

Experiment 4c: Mud resistivity Measurement

Aim and objective of the experiment: To measure the resistivity of different samples of mud using a

resistivity meter.

Observation: A calibrated resistivity cell was used to measure the resistivity of the different samples

of mud. The lap instructor filled the clean, dry resistivity cell with fresh mud sample. He then

calculated the resistivity to the nearest 0.01 ohm-meter by connecting the cell to the device. The

temperature was also measured and recorded. The table of results below shows the resistivity and

temperature for different mud samples.

Results:

Mud sample Resistivity in ohm meters Temperature (°C),( °F)

1 2.7 19.3, 66.74

2 2.8 19.6, 67.28

3 5 19.6, 67.28

From the table above, we can see that mud sample 1 and 2 have a similar resistivity where as mud 3

has a comparatively higher resistivity. This is due of the composition of mud 3. Mud 1 and 2 were a

mixture of bentonite and barite whereas mud 3 contained 0.15%of polymer. The polymer increased

the viscosity of the mud which increases the resistivity.

Conclusions and recommendations

pH and resistivity meters were used to determine the pH values of the mud in sample 1, 2 and 3. It

can be concluded that the pH of all the three mud were maintained greater than 7 inorder to reduce

corrosion and avoid flocculation. The mud resistivity calculated showed that the composition plays a

vital role in determining the resistivity. Polymers add to the resistivity. The precision of this

experiment could be improved by measuring the pH and resistivity over a number of times. The

accuracy can be improved by using different equipment inorder to decrease the significant errors.