سیالات حفاری

معماری فرهنگ قوم لر حفاری وسیالات حفاری تمدن لرستان

 
mud testing
نویسنده : رضا سپهوند - ساعت ۱٢:٢٥ ‎ق.ظ روز ۱۳٩۱/۱/۱٧
 

PREFACE

 

The purpose of this manual is two fold: first to acquaint the Drilling engineering students with the basic techniques of formulating, testing and analyzing the properties of drilling fluid and oil well cement, and second, to familiarize him with practical drilling and well control operations by means of a simulator. To achieve this objective, the manual is divided into two parts.

 

The first part consists of seven experiments for measuring the physical properties of drilling fluid such as mud weight (density), rheology (viscosity, gel strength, yield point) sand content, wall building and filtration characteristics. There are also experiment for studying the effects of, and treatment techniques for, common contaminants on drilling fluid characteristics. Additionally, there are experiments for studying physical properties of Portland cement such as free water separation, normal and minim-um water content and thickening time.

In the second part, there are five laboratory sessions that involve simulated drilling and well control exercises. They involve the use of the DS-100 Derrick Floor Simulator, a full replica of an actual drilling rig with fully operations controls, which allow the student to become completely absorbed in the exercises as he would in an actual drilling operation. The simulator has realistic drilling rig responses that are synchronized to specific events, like rate of penetration, rotary table motion, and actual rig sounds such as accumulator recharge, break draw works, etc.

It is hoped that the material in this manual will effectively supplement the theory aspect presented in the main course.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TABLE OF CONTENTS

PART  I:  DRILLING  FLUID 

 

 

Preface …………………………………………………………………...…....i

Table of Contents …………………………………………………..………...ii

Laboratory Safety Instructions……………………………………………...iii

 Experiment No. 1: Mud Weight, Marsh Funnel Viscosity and pH...................................... 4

 Experiment No. 2: Mud Rheology Test ……………………………………....11

 Experiment No. 3: Filtration, Wall Building and Resistivity ………………..16

Experiment No. 4. Mud Weight Control ……………………………………..21

Experiment No. 5. Drilling Fluid Contamination Test………………………. 24

Experiment No. 6. Solid, Liquid Content and Emulsion Characteristic                                of Drilling Fluids………….…………………………………………………27

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LABORATORY SAFETY INSTRUCTIONS

 

Safety in the laboratory must be of vital concern to all those engaged in experimental science work. It is therefore the responsibility of everyone to adhere strictly to the basic safety precautions provided and to avoid any acts of carelessness that can endanger his life and that of others around him. It is equally important to always abide by all the instructions for conducting the experimental work during the laboratory sessions. Below are some guidelines for general laboratory safety and procedures:

 

1-All students must be familiar with the locations and operational procedures of the

Emergency Shower, Fire Extinguishers, Gas Masks and Fire Blankets. These safety

devices pictured below.

 

2- Laboratory coats, safety glasses and safety shoes MUST be worn at all times during the laboratory session  NOTHOABS and open sandals are allowed during the laboratory sessions.

 

3- Eating, drinking and smoking are strictly. PROHIBITED in the laboratory at all times. Laboratory glassware should NEVER be used for drinking purpose.

 

4- Report any injury immediately for First Aid treatment, no matter how small.

 

5- Report any damage to equipment or instrument and broken glassware to the laboratory instructor as soon as such damage occurs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.   EXPERIMENT NO. 1

1.1.  MUD WEIGHT, MARSH FUNNEL VISCOSITY AND PH

       1.1.1.     MUD WEIGHT or DENSITY   TEST:

Theory :

 

The density of the drilling fluid must be controlled to provide adequate hydrostatic head to prevent influx of formation fluids, but not so high as to cause loss of circulation or adversely affect the drilling rate and damaging the formation.

Normal pressure gradient by water is equal to (0.433 psi/ft) and equal to 433 psi/1000 ft.

 

Test Equipment

 

The Baroid Mud Balance as shown below is used to determine density of the drilling fluid. The instrument consists of a constant volume cup with a lever arm and rider calibrated to read directly the density of the fluid in ppg (water 8.33), pcf (water 62.4), specific gravity (water = 1.0) and pressure gradient in psi/1000 ft. (water 433 psi/1000 ft.)

 

 

 

Figure 1.1: Typical Mud Balance

 

Calibration

 

1.Remove the lid from the cup, and completely fill the cup with water.

2.Replace the lid and wipe dry.

3. Replace the balance arm on the base with knife-edge resting on the fulcrum.

4. The level vial should be centered when the rider is set on 8.33. If not, add to or remove shot from the well in the end of the bream.

 

Test Procedure

  1. Remove the lid from the cup, and completely fill the cup with the mud to be tested.

 

  1. Replace the lid and rotate until firmly seated, making sure some mud is expelled through the hole in the cup.

 

  1. Wash or wipe the mud from the outside of the cup

 

  1. Place the balance arm on the base, with the knife-edge resting on the fulcrum.

 

  1. Move the rider until the graduated arm is level, as indicated by the level vial on the beam.

 

  1. At the left-hand edge of the rider, read the density on either side of the lever in all desired units without disturbing the rider.

 

   7.     Note down mud temperature corresponding to density.

 

 

1.1.2.  MUD VISCOSITY:

 

Theory :

The viscosity of a fluid is defined as its resistance to flow. The desired viscosity for a particular drilling operation is influenced by several factors, including mud density, hole size, pumping rate, drilling rate, pressure system and requirements, and hold problems. The indicated viscosity as obtained by any instrument is valid only for that rate of shear and will differ to some degree when measured at a different rate of shear. For field measurements the marsh funnel has become the standard instrument. For laboratory, the Fann V-G meter, a direct indicating rotational multi-speed instrument, has become the standard, allowing measurements of plastic viscosity, yield point, gel strength to be made

The Stormer viscometer is still, however, used to some extent for single point (apparent) viscosity and 0-10 min. gel.

 

Test Equipment

The Marsh Funnel is a device that is common to every drilling rig. Details of the Marsh Funnel and receiving cup are shown in Figures 1-2, and 1-3. The viscosity is reported in seconds allowed to flow out of the funnel. API specifications call for 1500 ml and one quart (946) ml out. For API water at 70 F + 0.5 oF  = 26 + 0.5 sec. The Marsh Funnel measures the apparent viscosity.

 

Calibration :

Fill the funnel to the bottom of the screen (1500 ml) with water at 70 F (plus or minus 0.5 F) time of outflow of the quart (946 ml) should be 26 seconds plus or minus 1/2 second

 

 

Figure 1.2: Marsh Funnel and One-liter Cup

 

 

 

 

 

 

Fann VG Meter

 

Test Procedure

 

 

1.    With the funnel in an upright position, cover the orifice with a finger and pour the freshly collected mud sample through the screen into a clean, dry funnel until the fluid level reaches the bottom of the screen (1500 ml).

2.   Immediately remove the finger from the outlet and measure the time required for the mud to fill the receiving vessel to the 1-quart (946 ml) level.

3.    Report the result to the nearest second as Marsh Funnel Viscosity at the temperature of the measurement in degrees Fahrenheit or Centigrade.

 

1.1.3.       HYDROGEN ION CONCENTRATION (PH):

Theory :

The acidity and the alkalinity of the drilling fluid can be measured by the concentration of the (H+) ion in the fluid. As for instance, if H+ is large
(I x 10-1), then the (OH-) hydroxyl concentration is very low (1 x 10­13),the solution is strongly acidic. If the (OH-) concentration is (1 x 10­1)very high then (H+) concentration is very low then the solution is strongly alkaline. The pH of a solution is the logarithm of the reciprocal of the (H+) concentration in grams moles per liter, expresses as:

PH = 

Example: If the solution is neutral then H+ and OH- concentrations are the same equal to 1 x 10-7.

PH = log

 

Therefore, if the pH of a mixture drops from 7.0 to 6.0, the number of (H+) increase ten times.

The pH of a mud seldom is below 7 and in most cases fall between 8 and 12.5 depending upon the type of mud. The pH is important because the pH affects the solubility of the organic thinners and the dispersion of clays presents in the mud.

 

 

Methods of measuring pH in the laboratory:

 

1.      The pH Paper: The pH papers strips have dyes absorbed into the paper display certain colors in certain pH ranges. It is useful, inexpensive method to determine pH in fresh water muds. The main disadvantage is that high concentrations of salts (10,000 ppm chloride) will alter the color change and cause inaccuracy.

 

2.       The pH Meter: The pH meter is an electric device utilizing glass electrodes to measure a potential difference and indicate directly by dial reading the pH of the sample. The pH meter is the most accurate method of measuring pH.

 

Figure 1.3 : Hydrion pH Dispensers .

 

                                       

Figure 1.4 : pH Meter

EXPERIMENT

 

The Laboratory Test:

 

1-           Take 2 samples of mud from each of the mud tanks.

 

2-           Stir the samples for 2 minutes and determine:

                          (a)       The Mud Weight

                        (b)      Marsh Funnel Viscosity in seconds

                          (c)      pH value using      - pH meter

-          Hydrion papers

 

RESULTS OF MUD PROPERTIES TEST WATER BASED MUD

(Density, Viscosity, pH)

Room Temp :            °F/          °C

Sample

No.

Mud Weight

Viscosity

 

(Marsh Funnel)

PH

(Hydrogen Ion Conc.')

 

 

ppg

psi/1000

pcf

Sec.

Phydrion

PH Meter

l.

 

 

 

 

 

 

2.

 

 

 

 

 

 

 

 

 

QUESTIONS ON EXPERIMENT NO. 1

 

Answer the following:

1..         List any five (5) very important functions of the drilling fluid?

 

 

2.        What requirements should a drilling fluid meet?

 

 

3.           Using the mud weights (ppg) obtained for Samples #1 and 2 of your experiment, calculate, how much hydrostatic pressure that each sample will exert on a formation at a depth of 10,000 ft.

 

 

4.        What is the difference between Over-balance and Under-balance?

 

 

5.        Estimate the mud weight needed to balance a formation pressure equivalent to 10,000 ft. depth with 0.561 psi/ft. pressure gradient

2.  EXPERIMENT   NO. 2  

 

2.1.            MUD RHEOLOGY TEST


Viscosity, Gel Strength and Yield Point

 

Introduction

 

Rheology refers to the deformation and flow behavior of all forms of matter. Certain rheologic measurements made on fluids, such as viscosity, gel strength, etc. help determine how this fluid will flow under a variety of different conditions. This information is important in the design of circulating systems required to accomplish certain desired objectives in drilling operations

 

 

2.1.1.      VISCOSITY:

 

          Theory :

 

Viscosity is defined as the resistance of a fluid to flow and is measured as the ratio of the shearing stress to the rate of shearing strain.

Two types of fluid characterizations are:

1.     Newtonian (true fluids) where the ratio of shear stress to shear rate or viscosity is constant, e.g. water, light oils, etc. and

2.    Non-Newtonian (plastic fluids) where the viscosity is not constant, e.g. drilling muds, colloids, etc.

                                

                                    300                           600

 RPM SETTING            

Figure 2.1: Flow Curves of Newtonian and non-Newtonian Fluids

Test Equipment

 

The Baroid (Model 286) Rheometer is a coaxial cylindrical rotational viscometer, used to determine single or multi-point viscosities. It has fixed speeds of 3 (GEL), 100, 200, 300 and 600 RPM that are switch selectable with the RPM knob.

                       

 

Figure 2.2: Variable Speed Rheometer

 

Additionally, the same switch set to the VAR position enables speed selection of between 3 and 625 RPM, by manual adjustment of the variable knob.

 

 

VISCOSITY MEASUREMENT PROCEDURE

 

1.                 Place a recently agitated sample in the cup, tilt back the upper housing of the rheometer, locate the cup under the sleeve (the pins on the bottom of the cup fit into

the holes in the base plate), and lower the upper housing to its normal position.

 

2.       Turn the knurled knob between the rear support posts to raise or lower the rotor sleeve until it is immersed in the sample to the scribed line.

 

 

3. Stir the sample for about 5 seconds at 600 RPM, then select the RPM desired for the best.

 

4.  Wait for the dial reading to stabilize (the time depends on the sample's characteristics).

 

5.  Record the dial reading and RPM.

RHEOLOGICAL CALCULATIONS

 

  1. 1.              Plastic viscosity (in centipoises-up):

 

 

Plastic Viscosity = PV= 600 RPM reading  -  300 RPM Reading

 

  1. 2.              Apparent Viscosity (in centipoises-cp):

 

 

    Apparent Viscosity = AV = 600 RPM Reading    2

 

 

  1. 3.              Yield Point (in lb/100 ft2):

 

 

Yield Point = Y.P = 300 RPM Reading  -   Plastic Viscosity

 

2.1.2.      GEL STRENGTH:

 Theory :

The Baroid Rheometer is also used to determine the Gel strength, in lb/100 sq.ft., of a mud. The Gel strength is a function of the inter-particle forces. An initial 10-second gel and a 10-minute gel strength measurement give an indication of the amount of gellation that will occur after circulation ceased and the mud remains static. The more the mud gels during shutdown periods, the more pump pressure will be required to initiate circulation again.

Most drilling muds are either colloids or emulsions which behave as plastic or non-Newtonian fluids. The flow characteristics of these differ from those of Newtonian fluids (i.e. water, light oils, etc.) in that their viscosity is not constant but varied with the rate of shear, as shown in Figure 2.2. Therefore, the viscosity of plastic fluid will depend on the rate of shear at which the measurements were taken.

 

Gel Strength Measurement Procedures

  1.    Stir a sample at 600 RPM for about 15 seconds.
  2.    Turn the RPM knob to the STOP position.
  3.    Wait the desired rest time (normally 10 seconds or 10 minutes).
  4.    Switch the RPM knob to the GEL position.
  5.    Record the maximum deflection of the dial before the Gel breaks, as the

Gel strength in lb/ 100 ft2.        (lb/100 ft25.077 = Gel strength in dynes/cm2).

 

2.1.3.     YIELD POINT(YP):

         Theory:

 

This is the measure of the electro-chemical or attractive forces in the mud under flow (dynamic) conditions. These forces depend on (1) surface properties of the mud solids, (2) volume concentrations of the solids and (3) electrical environment of the solids. The yield point of the mud reflects its ability to carry drilled cuttings out of the hole.

 

Measurement:

 

 
   

 

                                    YP = 300 RPM - Plastic Viscosity

 

 
   

 

 

 

Experimental Procedure

1.     Obtain a recently agitated mud sample from each of mud tanks (1) and

 

2.       Using the Baroid Rheometer, obtain dial readings at 3, 300 and 600

RPM.

 

3.   By means of the Theological calculations procedure, determine the Apparent and Plastic Viscosities, Yield Point and initial 10 sec. and final 10-minute Gel Strength parameters.

 

4.    Tabulate your results as in the given table below:

 

 

 

 

 

 

 

 

 

MUD RHEOLOGY TEST WATER BASE MUD

 

Sample

No.

VISCOSITY

 CP

Gel strength lb/ 100 ft2

θ600

θ300

PV

 

AV

 

YP

lb/100 ft2

Initial

 (10 sec.)

 

Final

(10 min).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

QUESTIONS ON EXPERIMENT NO. 2

 

1.      (a)     What is Plastic Viscosity?

        (b)    What does it characterize?

        (c)    What is the difference between the Plastic Viscosity and Apparent  

          Viscosity of a drilling fluid?

 

2.       Which role does Gel Strength play in the drilling process?

 

3.       What type of fluids does drilling fluid belong to?

 

4.          (a) What is the Yield Point?

            (b) What does it characterize?

            (c) What is the difference between Gel Strength and Yield Point of a

          drilling mud?

 

5.     Explain what you know about one point and two points curve fluids? Give one example of each type of fluid.

 

 

 

 

 

 

 

 

 

3.  EXPERIMENT NO. 3

 

3.1.   FILTRATION, WALL BUILDING, AND RESISTIVITY

 

3.1.1.      FILTRATION:

 

   Theory:


The loss of liquid from a mud due to filtration is controlled by the filter cake formed of the solid constituents in the drilling fluid. The test in the laboratory consists of measuring the volume of liquid forced through the mud cake into the formation drilled in a 30 minute period under given pressure and temperature using a standard size cell.

 

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, i.e.

 

α  √t

 

The two commonly determined filtration rates are the low-pressure, low temperature and the high-pressure high-temperature.

 

 

Test Equipment

 

The low-pressure test is made using standard cell under the API condition of 100 ± 5 psi for 30 minutes at room temperature. Another special cell will be used to measure filtration rate at elevated temperatures and pressure. Filter press used for filtration tests consists of four independent filter cells mounted on a common frame.

 

Each cell has its own valve such that any or all the cells could be operational at the same time. Toggle valve on the top of each cell could be operated independently for the supply of air for each individual cell. Special high pressure and high temperature filtration tests are run in the laboratory simulating formation temperature and formation back- pressure.

 

 

 

 

TEST PROCEDURE FOR FILTRATION RATE AT 100 PSI & ROOM

TEMPERATURE

  1.       Detach the mud cell from filter press frame.

 

  1.      Remove bottom of filter cell, place right size filter paper in the bottom of the cell.

 

  1.     Introduce mud to be tested into cup assembly, putting filter paper and screen on top of mud tighten screw clamp.

 

  1.    With the air pressure valve closed, clamp the mud cup assembly

to the frame while holding the filtrate outlet end finger tight.

 

  1.    Place a graduated cylinder underneath to collect filtrate.
  2.    Open air pressure valve and start timing at the same time.

 

  1.    Report cc of filtrate collected for specified intervals up to 30 minutes.

 

          8.    Tabulate the results in an appropriate table.

3.1.2.   WALL BUILD:

 

MEASUREMENT PROCEDURE FOR MUD CAKE THICKNESS

(32nd of an inch or cm)

 

It should be reported in thirty-second of an inch in whole number. Vernier caliper could be used to measure the thickness, however, while measuring care should be taken not to press vernier jaw on mud cake to penetrate through.

Results on mud cake thickness should be reported in whole number.

 

Example: 0.75/32" should be reported as 1/32.

                i.e. closest to the whole number.

                Likewise 1.75/32" should be reported as 2/32"

 

 

3.1.3.   MUD RESISTIVITY:

 

Theory :

 

The resistivity (Wm) of a drilling mud is influenced by the dissolved salts (ppm) or (gpg, grain per gallon) in the water portion and the insoluble solid material contained in the water portion. The greater the concentration of dissolved salts, the lower resistivity of the solution. Unlike metals, the resistivity of a solution decreases as temperature increases. It is necessary to measure resistivity because the mud, mud cake, mud filtrate resistivity exert a strong effect on the electric logs taken in that mud. The mud resistivity varies greatly from the actual resistivity values due to the various factors encountered in the actual operation.

 

 

Test Equipment

 

Equipment used is the Baroid Resistivity Meter (Fig. 3.3).

 

 

 

 

 

 

Figure 3.3: Analog and Digital Resistivity Meters

 

 

(i)       MEASUREMENT  PROCEDURE  FOR  MUD  CAKE  ESISTIVITY

 

  1. Remove excess water from filter cake.

 

  1. Fill the slot on top of the cell with mud cake.

 

  1. Press black button and adjust for full scale.

 

  1. While keeping the black button depressed, press red button.

 

  1. Reading on the meter is the resistivity of mud cake.

 

  1. Record the resistivity of the mud cake and the temperature of the cell.

 

7.    Remove the cell and clean thoroughly with distilled water

 

 

( ii)     MEASUREMENT  PROCEDURE  FOR  MUD  FILTRATE  RESISTIVITY

 

  1. Fill cell with mud and remove excess mud from the top of the cell surfaces).

 

  1. Connect cell to the resistivity meter.

 

  1. Press black button and adjust for full scale reading on the meter.

 

  1. While keeping the black button depressed, press the red button.

 

    5.         The reading on the meter is the resistivity of the mud (when testing mud it may be necessary to allow 3-5 minutes after putting mud in the cell before taking a reading to allow cell and the mud filtrate to reach temperature equilibrium).

 

   6.        Record the resistivity reading and the temperature of the cell.

 

   7.       Remove the cell and clean with distilled water. (Pipe cleaner can be

used to remove particles of mud filtrate that cannot be flushed out with water).

 

 

 

QUESTIONS ON EXPERIMENT NO.3

 

1 .    By comparing the Spurt Loss of Sample # 1 and Sample #2 in part A of your experiment results , determine which of the two samples plugs the filter paper faster and explain why .

 

2.      Describe how the filter cake is formed on the walls of a hole during a normal drilling operation.

 

3.    What are the factors controlling the rate of filtration ?

 

4.     What is sloughing of shale and how can it be controlled ?

 

 

 

 

 

 

 

 

 

4.  EXPERIMENT NO. 4

 

4.1.  CONTROL OF MUD WEIGHT

4.1.1.    EFFECT OF ADDING BENTONITE ON MUD PROPERTIES FOR FRESH AND SALT WATER BASE MUD:

 

 

Procedure

 

1.           Add to every 400 c.c batch of fresh water base mud 2 4, 6 and 8 grams of

bentonite and stir for 10 minutes.

 

2.     Measure the density lb/gal, viscosity c.c. (Apparent and plastic) and yield point Ib/100 ft, using the Rheometer for every batch.

 

3.    Add 20.6 ml of 10% by weight salt water to every batch. Stir for 5 minutes and repeat step (2).

 

4.       Report all the results (density, viscosities, yield) for every batch in a

convenient table. Plot them versus the amount of bentonite in gram in two

plots, one for fresh water and the other for salt water.

 

 

Discussion:

 

Include the following points in your discussions:

 

1.     Discuss the effect of adding bentonite on density.

2.     Discuss the effect of adding bentonite on the rheological properties.

3.      Correlate and justify the results obtained for fresh and salt water.

4.      What is the effect on yield point?

 

 

4.1.2.       EFFECT OF ADDING WEIGHT MATERIAL (BARITE):

 

Theory

Barite was first used, in California, in a well being re-drilled with cable tools in 1923. According to that case, density of the mud was raised to 90 lb/ft3(1.44 gr/cm3 to control gas in flow and to stop caving.

One function of barite has developed - the preparation of a temporary high- density plug formed from slurry of a barite in water (2.65  SG). Such slurry contains the maximum concentration of barite that is used - about 750 lb/bbl

(2 100 kg/cm3).The minimum concentration of barite might be as low as 10 lb/bbl (28 kg/m3), although usually it would be substantially higher.

The quantity of barite required to raise the density of a given volume of mud a specific amount can be readily calculated from the relation, in consistent units:

 

 

 
   

 

 

 

 
   

 

Where

 

              Pf =  Final Mud Density

              Po  = Original Mud Density

              P= Barite Density = 35.82 ppg  

              Vo = Vo= Original Mud Volume

              VB = Barite Volume

              WtB  = Barite Weight

 

Test Procedure

 

  1. Calculate and list the amount of barite required increasing the density of each batch from 8.6 ppg to 9, 10, 11 and 12 ppg.

 

  1. Obtain 400 cc of original base mud (density 8.6)

 

     3.   Add the calculated amount of barite to each batch, stir for about 2 minutes and measure the Apparent and Plastic Viscosities and Yield Point.

    4.      Repeat step 3 for Salt water-base mud

    5.    Tabulate the results and plot the density (ppg ), viscosity (apparent and plastic) and yield point versus the amount of barite added..

 

 

4.1.3.       WATER-BACK (ADDING WATER TO A CHEMICALLY TREATED MUD):

 

  1.    Obtain a 350 c.c. Of water base mud of 13.5 ppg weight and 9.5 pH.

 

  1.   Add water incrementally and measure the Mud weight every time to reach 10.5 ppg and same (9.5) pH.

 

  1.    Measure the viscosity and gel-strength and check if any change occurred.

 

  1.    List your results in an appropriate table.

 

 

 

QUESTIONS ON EXPERIMENT NO. 4

 

  1. List the advantages obtained by adding weighting material to mud.

 

  1. List three (3) names of weighting material.

 

  1. What are the disadvantages of adding solids to the water based mud?

 

     4.     Give reasons for adding water to your mud.

 

 

 

 

 

 

 

 

 

5.  EXPERIMENT NO. 5

5.1.  DRILLING FLUID CONTAMINATION TEST

 

 

Introduction

In preparing a bentonite slurry using fresh water, the bentonite will hydrate and agitation furnished by a mixer is sufficient to separate the hydrated clay plate lets and result in a viscosity and gel strength increase, if the bentonite is placed in salty water or water containing dissolved hardness (calcium or magnesium) the hydration and subsequent dispersion by agitation is reduced.

The question arises, what occurs when salt or hardness is added to a dispersed bentonite drilling fluid and what is necessary to return the slurry to an acceptable condition for drilling?

In this test we will study the effect of contamination of monovalent chemicals (NaCI and KC1) and divalent chemicals that cause contamination are calcium sulfate (CaSO4), cement (Ca (OH)2 ), and Gypsum (CaSO4 – 2H2O). These soluble salts are commonly encountered during drilling, completion or workover operations.

 

 

TEST PROCEDURE FOR MUD CONTAMINATION

1.    Test base mud for weight ppg, Plastic Viscosity cp, Apparent Viscosity

c.p., Yield Point lb/100 ft2.

 

2.      Add to 400 ml base mud, 0.75, 1.5, 2.5, 3.5 and 5.0 grams NaCl and

repeat step (1) after each addition (stir every time).

 

3.    Add to a new 400 ml base mud 0.75, 1.5, 2.5, 3.5 and 5.0 grams Gypsum (CaSO4 - 2H2O) and repeat step (1) after each addition (stir every time).

 

4.     Add to a new 400 ml base mud 0.75, 1.5, 2.5, 3.5 and 5.0 grams anhydrite (CaSO4) and repeat step (1) after each addition (stir everytime).

 

5.      Report the results in a convenient table for the three contaminants and plot in three different plots the effect of contamination with salt, gypsum and anhydrite on mud density and viscosities and yield point.

TREATMENT OF THE CONTAMINATED DRILLING FLUID

5.1.1.        SALT CONTAMINATION:

Test Procedure

1.    Test 525 ml of the base mud sample for weight ppg, viscosity cp, yield point Ib/100 ft2 and pH.

 

2.    Add 27 ml of 10% by wt salt water (NaCI) to the base mud sample (525 ml) stir 2 minutes after adding salt. Age for about 15 minutes and stir again for 2 minutes. Determine its viscosity, density and pH.

 

3.    Add to the contaminated sample 1/2 cc increments until the original viscosity is restored.

 

4.    Continue to add (SAPP) in 1/2 cc increments until the original viscosity is restored.

 

5.     Plot the result on a curve showing the viscosity and pH as a function of (SAPP) concentration.

 

 

5.1.2.         GYPSUM  CONTAMINATION:

 

Test Procedure:

  1. Repeat step No. 1 in (A).

 

2.      Contaminate the base mud by (525 ml) with 6 gr of Gypsum, stir for 3

minutes. Age the sample for 15 minutes and stir again for 2 - 3 minutes.

Determine the viscosity cp and density ppg and pH.

 

3.    Add 3 gr soda ash (Na2CO3) to remove the hardness from sample in step # 2. Stir for 10 minutes and test.

 

4.   Add 4 gr Carbonox and 1 gr of Caustic Soda to sample in step # 3. Stir 10 minutes and test.

 

5. Add 4 gr Gypsum to a 525 ml sample of base mud and stir 10 minutes

 and add 5 gr Q-Broxin and 3/4 of Caustic Soda. Stir 10 minutes and test.

5.1.3.      CEMENT CONTAMINATION:

 

Test Procedure

1.      Repeat Step No. 1 in (A).

 

  1. Contaminant the base mud (525 ml) by 1.0 PPB and stir for two minutes. Age for 15 minutes. Stir and test.

 

3.    Add to the contaminated sample 1/2 cc (SAPP).

 

4.   Continue to add SAPP in 1 /2 cc increments until the original viscosity is restored measure pH every time.

 

5.   Plot the result on a curve showing the viscosity and pH as function of (SAPP) concentration.

 

6.    Add to the base mud 1.5 cc (SAPP) and 1.0 Sodium Bicarbonate and stir for 10 minutes.

 

7.    Add 1.0 gr of cement while mixing the sample after aging and test.

Experimental Results

Tabulate all results in the appropriate table and present graphs where necessary.

 

 

 

QUESTIONS ON EXPERIMENT NO. 5

 

1.     Would it be better to treat the mud before or after cement contamination? Discuss this question using your experimentally obtained data.

2.     Discuss and compare the effectiveness of various materials in treating contaminated muds.

  1. Did the CARBONEX treated Gypsum contaminated mud or the Q­BROXIN treated Gypsum contaminated mud exhibit better flow properties? State why?

 

 

 

6.  EXPERIMENT NO. 6

 

6.1.   SOLID & LIQUID CONTENT AND EMULSION CARACTERISTICS
OF DRILLING FLUID

 

6.1.1.   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.

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6.1 : Sand Content Set

 

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.

 

  1. 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.

 

 

Results

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

 

Core 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.

 

  1. 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.

 

 

 

6.1.2.  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

 

Figure 6.2 : Fann Emulsion and Electrical Stability Testers

 

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 XI 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.

 

2.      Do not short out electrodes.

 

6.1.3.      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).

 

 

 

 

Figure 6.3 : Oil/Water Retort Kit

 

 

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.

 

 

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.

 

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.

 

Care of Equipment

 

Before each retorting the following should be done:

1.       Use the spatula to scrape the dried mud from the mud chamber and lid to

assure correct volume.

 

2.     Remove and replace any mud-caked steel wool.

3.    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

 

A-      % oil by volume                             = ml oil x 10

B-      % water by volume                         = ml water x 10

C-       % solids by volume                      = 100 - (ml oil + ml water) x 10

*D-    Grams oil                                       = corrected ml oil x 0.8

E-       Grams water                                   = ml water

F-        Grams mud                                   =  lb/gal mud weight x 1.2

G-       Grams solids                                 =   F- (D+E)

H-       ml solids                                       = 10 - (ml oil + ml water)

I-        Average specific gravity of solids          =

J-      Solids % by weight                          =

K-    High gravity (4.3)  solids % by volume      = (I - 2.5) x 55.6

L-    Low gravity (2.5) solids   % by volume         = 100-K

 

* Corrected ml of oil  = ml of oil

 

 

 

Table 6. 1 :  Specific Gravity and Percent by Weight of Mud Contents

 

Sp. Gr. of Solids

2.6

 2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.3

%by Weight Barite

0

18

34

48

60

71

81

89

100

%by Weight Clay

100

82

66

52

40

29

19

11

0

 

Presentation of Experimental Results

1. Using your calculated results of the average specific gravity of solids, determine the solid content of each of the samples from Table 6.1 (either directly or by interpolation, which ever the is applicable).

2. Present the results of your findings in (1) in an appropriate table.

 

 

 

QUESTIONS ON EXPERIMENT NO. 6

 

(1)      From the results of your experiment in part (A), is there a correlation between the mud weight of the sample and the % sand by volume?

Explain.

 

(2)    What problems are you likely to encounter during drilling operations if you have a high sand content in your drilling mud?

 

(3)   What is the importance of conducting Emulsion Stability tests on drilling fluids?

 

(4)     From the results of your experiment in part (C), which of the samples has the highest clay content?

 

 

 

 

 

 

 

7.    APPENDICES

 

 

7.1.    A PPENDIX  A:         REFERENCES  

 

  1. Manual of Drilling Fluid Technology, NL Baroid/NL Industries Inc. 1979, 3-24, 37-39.
  2. API Specification for Material and Testing for Well Cements, 2nd Edition, API Production Department, Washington D.C., (June 1984). 18-47.
  3. 3.      Simtran Drilling Simulator Operating Manual, Simtran corporation,  Medway, Massachusetts, (July 1980), 1-65

7.2. APPENDIX   B:        FORMAT FOR LABORATORY REPORTS

Laboratory reports should be prepared in a style roughly comparable to that of a research paper. They should be typed, or neatly handwritten, using one side of the page only. While accuracy of data and calculations will account for about 60% of the grade, neatness and clarity of presentation are important and will constitute the other 40%. Use the following format as guide in preparing reports:

7.2.1.   TITLE PAGE

The title page serves as a cover for the report. Its main function is to identify the author and the subject of the report. It should include the following:

       (a)    Course and section numbers

       (b)    Experiment number

       (c)    Title of experiment

       (d)    Name, LD. # and Group #

       (e)    Date experiment was performed

       (f)    Date experiment was submitted

 

7.2.2.   INTRODUCTION

This section should give a brief discussion of the general background and basic theory of the subject in the report. Pertinent equations can be included if any.

7.2.3.   OBJECTIVE OF EXPERIMENT

This should be a brief statement of the purpose of the experiment

 

 

7.2.4.  PROCEDURES

This section should describe the steps used in securing the experimental data. The description must be in sufficient detail so that the reader could repeat the experiment by using this stated account of the procedure. Write what you did and do not repeat the instructions.

 

7.2.5.  RESULTS

The final results obtained from analyzing the raw data of the experiment are (given in this section. These can be presented in tabulated or graphical forms. All tables and figures should be labeled and given sequence of proper identification. All graphs should be made on standard graph paper, with the data clearly connected with smooth curves or straight lines, which ever is applicable. Intermediate data used in obtained the result should not be included in this section.

7.2.6.  SAMPLE CALCULATION

Where a calculation is required in connection with the results of an experiment, one complete sample calculations should be included. The equation used should be indicated and all variables used in the equation should be cited.

7.2.7.  DISCUSSION OF RESULTS

This section is used to explain the data given in the results section. Brief comment should be made on the experimental errors, data reproducibility and

Discrepancies between experimental and theoretical results. A description of the practical application of the results can also be included.

 

 

 

7.2.8.   ANSWERS TO GIVEN QUESTIONS

Answer any questions given at the end of each lab material.                           References and material for these questions can be found in the laboratory manual as well as your course textbook.

 

7.2.9     REFERENCES

The sources of any literature referred to in the report should be listed in order of appearance in the report. This should be in accordance with the standard format used in technical literature. For petroleum engineering subjects, the SPE standards should be adopted and this be arranged as follows:

         (a)   Author's last name followed by his initials

         (b)  The name of the book or article

          (c)   If it is an article, the name and volume of the journal.

                 (d)  If it is a book, the date of publication, publisher and edition

(e)   Page number

 

EXAMPLES:

(a) For a Book:

Katz, D.L., Cornell, D., Kabayashi, R., Poetman, F., Vary, J.A., Elenbass, J.R. and weinaug, C.F.: Handbook of Natural Gas Engineering, McGraw-Hill Book Co. Inc., New York, N.Y. (1959) 10-20.

(b) For a Paper:

Swift, G.W. and Kiel, O.C.: "The Prediction of Gas Well Performance Including the Effect of Non-Darcy Flow," J. Pet. Tech. (July, 1962) 791

 

 

7.3.   APPENDIX C: CLASSIFICATION, COMPOSTION AND PREPARATION OF DRILLING FLUIDS

 7.3.1 . CLASSIFICATION OF DRILLING FLUIDS

7.3.1.1.   WATER BASE FL UIDS:

                  (a)      Fresh water muds - little or no chemical treatment

                         1.       Spud Mud

                                       2.       Natural Muds

               (b)     Chemically treated muds - No calcium compounds added

                                     l.         Phosphate muds

                                       2.     Organic treated muds

                                                        (i) Lignite

                                                        (ii) Quebracho and other extracts

                                                        (iii) Chrome lignosulfonates

 

            (c )      Calcium treated muds

                       l.    Lime

                                    2.  Calcium chloride

                                    3.  Gypsum

          (d)        Salt water muds

                                  1.   Sea water muds

           2.   Saturated salt-water muds

 

                  (e)      Oil - Emulsion Muds (Oil-in-water)

                     Special modifications

                                   1.   Low solids oil-emulsion muds

                                   2.   Low clay solids weighted muds

            3.    Surfactant muds

 

 

 

 

 

7.3.1.2.   OIL BASE MUDS

       (a) Oil base muds

      (b) Inverted Emulsion Muds (water-in-oil)

                     (c)  GASEOUS DRILLING FLUIDS

                                  (i)   Air or Natural gas

               (ii)   Aerated muds

 

 

7.3.2.    COMPOSITION OF WATER-BASE MUD

 

7.3.2.1.            Water-base mud consists basically of:

 

                        (a)  Liquid phase

                                         (i)   Water

                                         (ii)   Oil

                                         ( iii) Emulsion

 

                       (b)   Solids phase - Inert, non-reactive components

                (i)    Sand, silica, limestone, chert, dolomite, etc.

              (ii)   Barite, Galena

 

 

                        ( c)  Colloidal phase - Small particle size

                                           (i)   Non-swelling

                  (ii)  Swelling clay – bentonite

 

                        (d)  Miscellaneous (Chemical phase)

                                           (i) Thinners, lost circulation material, dissolved solids, filtrate reducing agents, surfactants, corrosion inhibitors and other chemicals.

7.3.3 .   LABORATORY PREPARATIONS OF WATER BASE MUD

          1.      Add enough bentonite to calculated amounts of sweet water to give muds of specified densities in ppg. or pcf.

 

         2.     Stir these with the standard mixer for 30 min. After 25 minutes stirring scrape down by lumped material adhering to the spindle or side of the container. Adjust the pH to 9.5 ± 0.1 with either phosphoric acid or a caustic solution as required.

Resume the stirring for the period specified.

        3.      At the end of the stirring time transfer the samples to a sealed jar and age for 24 hrs at room temperature.

        4.      After aging, readjust the pH to 9.5 ± 0.1 as before stir the sample for 5 minutes and test immediately after stirring.

      5.   Measure the mud properties as in the proceeding experiments.

 

 

7.4.    APPENDIX D:  MISCELLANEOUS FORMULAS

     7.4.1.  Hydrostatic Head (Hs)

           (a)   Hs, psi/ft = 0.052 X mud wt., (ppg) or

                Psi = 0.052 X mud wt., (ppg) X depth, (ft.)

           (b)   Hs, psi/ft = 0.00694x(mud wt.,lb/ft3 ) or

                 Psi = 0.00694 X (mud wt., lb/ft3) X depth. ft.

              (c)   To estimate Hs the following rule can be used in the field:

One-half of the mud wt.in ppg is approximately equal to the hydrostatic head in psi 10 ft. or

 

 
   

 

Mud weight (ppg)         = psi/10 ft 2

7.4.2.    Estimation of volume displacement of barite: 15 sacks of Barite will increase the volume of a mud by approximately one barrel.

 

   7.4.3.  Hole Volume:

         Diameter of the hole (inches) squared is approximately equal to the hole          volume in barrel per 1000 ft.

bbl/1000 ft = (D, in)2

 

  7.4.4.  Pit volume, bbls   =  Length(ft) x Width(ft) x Depth(ft)

5.62 ft3/bbl

   Pit capacity bbl/inch = Volume, bbl = bbl/inch Depth, inches

7.4.5.    For laboratory purposes:

                   1 bbl = 42 gal.

                   1 bbl of water = 350 lbs., of water

 

 
   

 

                   1 bbl of water in the field = 350 cc of water in laboratory

 

 

 
   

 

     Therefore,

                   1 gr. / 350 cc  is equivalent to 1 lb./bbl.

                    

                   lb./ft3  =  7.5 * ppg.