Chapter 2 Mud Properties & Measurements

Question 1

How to measure Mud Properties?

Answer 1

• Basic Tests, Chemical Tests

Question 2

Basic Tests - to measure what?

Answer 2

• Density
• Rheology
• Filtration
• Solid Concentration
• % LGS - unwanted drill solids
• % HGS - weighting material concentration (barite)
• % sans content (we want low %)

Question 3

Chemical Tests - test what?

Answer 3

• pH (hydrogen)
• Alkalinities (Hydroxides & carbonates)
• Total hardness - Ca & Mg ions
• Total Chloride ions

Question 4

Weight Up Formula

Answer 4

= 1470 x (W2 - W1) / 35 - W2
=____ lb/bbl of barite required

Question 5

What is Mud Viscosity?

Answer 5

• Viscosity is the resistance of the fluid to flow
• Viscosity is required in addition to flow rate to clean the hole

Question 6

4 types to look into Viscosity

Answer 6

• Funnel Viscosity (FV)
• Plastic Viscosity (PV)
• Yield Point (YP)
• Low Shear Rate Viscosity (LSRV)

Question 7

Instruments to measure Mud Viscosity

Answer 7

• Marsh Funnel
• Fann Viscosmeter

Question 8

How to calibrate Marsh Funnel

Answer 8

• use SW
• it takes 26 second o filtrate out SW from Marsh Funnel

Question 9

Fann Viscometer

Answer 9

• All the readings must be done at 120 deg Fahrenheit (Std temperature for viscosity reading)
• High temperature, viscosity low

Question 10

What is Plastic Viscosity (PV)?

Answer 10

PV is a viscosity that is due to concentration of solids

PV (cps) = 600Q - 300Q

PV affects ECD - High PV, High ECD

To reduce PV, reduce solids

Question 11

What is Yield point (YP)?

Answer 11

YP is the viscosity due to the chemical attraction between the particles

YP=300Q - PV

YP can be affected by intentional solids - XC polymer, bentonite, contaminants

Question 12

Low Shear Rate Viscosity (LSRV)

Answer 12

• LSRV at 6 rpm & 3 rpm reading best represent the viscosity required in the annulus

Question 13

What is Gel Strength?

Answer 13

• Gel strength is the increase of viscosity at zero shear rate
• it is the measure of the attractive forces under static conditions
• It is measured by taking the 3rpm reading from fann viscometer after the mud is static for 10s,10mins,30mins
• Ability to suspend the cuttings.
• Flat gel is desired - less force needed to break the mud

Question 14

What is the effect of LOW viscosity?

Answer 14

• poor hole cleaning*
• overloading of the annulus increasing the hydrostatic*
• Increased erosion if the fluid is in turbulent flow
• barite sag or settlement*

Question 15

What is the effect of EXCESSIVE viscosities?

Answer 15

• Increased pump pressure
• Increased the risk of swabbing & surging the hole
• loss of mud at the shaker
• increased risk of fracturing the fm, especially with high gel strength
• poor mud removal for cementing ops

Question 16

What is Filtration?

Answer 16

• It is the loss of FILTRATE to a porous & permeable fm
• Occurs when the hydrostatic pressure > fm pressure, and there are adequate solids in the mud to form a filter cake
• Filtrate invasion ensure adequate FE, maintain wellbore stability & minimize reservoir damage
• Adequate filter cake will seal permeable fms & facilitate cementing & completion
• Solids in the mud usually forms as a filter cake which prevents excessive fluid loss

Question 17

A quality filter cake should be:

Answer 17

• thin
• low permeability
• have low friction coefficient

Question 18

Flocculated Filter Cake

Answer 18

• have spaces in bentonite layer. This allows filtrate to penetrate further
• Filtration invasion will be higher which lead to fm damage
• Filter cake will be too thick which lead to differential sticking
• Hence, add bridging materials/solids

*need to determine the bridging material size to minimize filtrate invasion

Question 19

2 types of Filtrations

Answer 19

• Static filtration
• Dynamic filtration

Question 20

Explain what is Static Filtration

Answer 20

• Occurs when the mud is not circulating
• cake thickness increases with time
• rate of filtration decreases with time
• static cake is thicker than dynamic cake

*Spurt loss= the vol of fluid that gets through the fm before filter cake is formed