Fundamentals of Drilling Mud: Section 1 Flashcards
Muds are composed of a three phase system:
(1) water (liquid phase)
(2) active solids
(3) inert solids
Active Solids
Clays that readily swell in water (Hydrophilic) giving viscosity to the fluid and designated as hydrophilic such as IMCO-Gel (bentonite)
Inert Solids
Solids in the drilling mud that do not hydrate or swell in the presence of water (hydrophobic), such as BaSO4, sand, shapes that do not hydrate
Hydrophillic
Swell in water
Hydrophobic
Does not hydrate or swell in the presence of water
What chemical is used to treat mud with a calcium excess of 120 ppm?
Soda ash
By increasing the weight the cuttings become more ________ and suspend better, resulting in a cleaner hole
buoyant
What is the pressure exerted on a column of fluid at rest called?
Hydrostatic pressure
Term used to describe the property of a fluid which causes it to build up a rigid or semi-rigid gel structure when allowed to stand at rest; yet the gel structure can be returned to a fluid state by mechanical agitation.
thixotropic
Commercial additives may be broken into two broad categories:
viscosifiers and weighting materials
There are two basic types of viscosifiers:
Clays and polymers
There are two types of commercial clays:
montmorillonite and attapulgite
Montmorillonite clays is used in two forms
Sodium and calcium
Sodium montmorillonite is the highest grade of clay and commonly called what?
bentonite (IMCO-gel)
Bentonite has the ability to swell up to how many times its size?
10
Calcium montmorillonite (IMC-Klay) has the ability to swell up to how many times its size?
2 to 4
Which clay yields as much viscosity in salty water as it does in fresh water?
Attapulgite Clay (IMCO-Brine gel)
True/False: Attapulgite/Brine gel is good for filtration control
FALSE
The term used to describe particle size and ability to remain in suspension
Colloidal
True/False: The atomic structure of commercial clays have a negative imbalance thus permitting water to pull it apart
TRUE
Which divalent ion is more highly charged than the monovalent sodium ion and forms a stronger bond thus preventing water molecules from swelling the particles to a greater degree?
Calcium montmorillonite (IMCO-Klay)
Which clay is harder to pry apart and flocs/aggregates in large units with void spaces between thus limiting the usefulness as a fluid loss reducer and borehole stabilizer?
Calcium montmorillonite (IMCO-Klay)
In a sodium chloride solution above __% salt, bentonite becomes impractical for use as a viscosifier. Why?
- Sodium tends to satisfy the negative imbalance of the particles, bonding the platelets so tightly it produces little hydration or swelling.
When bentonite becomes ineffective because of high salt content, which clay is used as a viscosifier?
Attapulgite Clay (IMCO-Brine gel)
True/False: Barite, calcium, carbonate and galena are used as viscosifiers
FALSE: weighting materials
The most commonly used material for increasing the density of muds is?
Barite (IMCO-Bar), BaSO4
Barite has a specific gravity of __ to __. Galena has a specific gravity of __ to __. Calcium carbonate has a specific gravity of __ to __.
- 2 to 4.3
- 5 to 6.7
- 7 to 10.8
True/False: Barite is used most often for emergencies such as killing wells.
FALSE: galena
Which chemical is used to increase the density of oil muds?
Calcium carbonate
What term is defined as the science of flow and deformation of matter (solid, liquid and gas)? In essence, it deals with the study of the ______-______-____ relationship of any matter.
Rheology. stress-strain-time
True/False: Viscosity is the most important rheological property of a fluid.
TRUE
Capillary viscometer is preferred when the data are used for ____ ____ problems.
Pipe flow
___ ________ is a measure of thixotropic under static conditions. It shows the amount of structure buildup during a static period due to the attractive forces between particles. _____ value is a measure of thixotropic under dynamic conditions.
Gel strengths
Yield
Starches, CMC, asbestos fibers, and bacterially-grown _______ are under the broad description of which type of viscosifiers
polymer
Excessive gel strengths can cause complications such as:
- __________ of air or gas in the mud, causing a lightening of the __________ column.
- Pump efficiency _______.
- Retards settling of sand and cuttings while drilling, causing an ________ in _______ and solids buildup.
- Swabbing on trips.
- _________ pressure surges breaking down the formation.
- Unable to get logging tools to the ______.
- Entrapment, hydrostatic
- Reduced
- Increase, density
- Excessive
- bottom
True/False. The treatment for excessive gel strengths is not the same for excessive yield point.
FALSE
The term for loss of fluid into permeable formations after these zones have been exposed to the drilling fluid through drilling operations.
Filtration or fluid loss
True/False: The rate of fluid loss is proportional to the amount of deposited cake.
TRUE
Without the deposition of filter cake, dynamic fluid losses are greatest where?
Below the bit
True/False: Laminar flow is susceptible to greater fluid loss than turbulent flow (generally adjacent to the drill collars).
FALSE. Turbulent flow is more prone to fluid loss.
Which filtration agent has the most favorable filtration control? And which filtration agent helps control dynamic fluid loss rate, particularly at elevated temperatures?
Starch
Lignosulfonate
In what ways does temperature effect filtration?
- Increased __________
- Attractive forces ________ with the change in the ionic atmosphere
- Organic colloids such as ______ and CMC break down under excessive temperatures.
- High temperatures may cause ___________ in muds containing _______, high alkalinities, and high solids
- solubility
- increase
- starch
- cementation, calcium
True/False: the filter cake becomes more compacted as pressure increases resulting in a change in the cake’s porosity and permeability.
TRUE
True/False: The addition of dispersants serves to soften the filter cake and thus increase fluid loss.
FALSE. It toughens and lowers
Benefits of soda ash:
- Removes calcium contamination
2. Decreases viscosity and gel strength
