Mud Composition

Mud Composition

Composition:
Phases

Phases of a Drilling Fluid

    Water (continuous) phase
    Reactive commercial clay solids
    Reactive formation (drilled) solids
    Inert formation (drilled) solids
    Inert commercial solids
    Soluble chemicals

Water phase

    Definition: The continuous (liquid) phase of the drilling fluid (mud)
    Can be fresh water, brackish water, sea water, saturated salt water, or another type of brine fluid
    Can be hard water containing a high concentration of calcium or magnesium

Fresh water
Usually available only on land locations
Advantages:
Commercial clays hydrate more
Most chemicals are more soluble
Disadvantages:
Formation clays hydrate  more, which can result in hole problems and damage to the producing zone
  Brackish water
Usually in a marine environment
Slightly salty
Higher calcium and magnesium than fresh water
Sea water
Chlorides and hardness varies
Chlorides in Gulf of Mexico 15,000 - 30,000 mg/l
Calcium in Gulf of Mexico 400 ± mg/l
Magnesium in Gulf of Mexico 1200± mg/l
Hardness in North Sea much higher
Saturated salt water
Used primarily to drill through large salt formations
Salt must be added to achieve saturation
Prevents hole enlargement due to leaching or dissolving salt from the formation
Leaching could result in hole problems and expensive mud and cement costs
Brine water
Usually used for clay (shale) inhibition
Potassium chloride (KCl)
Calcium Chloride CaCl2
Formates (Na+, K+)
Bromides
 Reactive solids
S.G. = 2.6, Density = 21.67 ppg
Commercial  clays
Sodium Montmorillonite or bentonite
M-I GEL
Attapulgite
SALT GEL
Formation clays (drilled solids)
S.G. = 2.6, Density = 21.67 ppg
Montmorillonite (swelling clay)
Illite (non-swelling clay)
Kaolinite (non-swelling clay)
Chlorite (non-swelling clay)
Gumbo Shale (combination of above clays)
Inert solids
Commercial
Barite (barium sulfate)
S.G. = 4.2, Density = 35 ppg
(M-I BAR)
Used to increase mud density up to maximum of 22 ppg±
Hematite (iron oxide)
S.G. = 5.0, Density = 41.67 ppg
Fer-Ox
Used to increase mud density up to maximum of 25 ppg ±
Calcium Carbonate
S.G. = 2.8, Density = 23.34 ppg
Acid soluble
Lo-Wate
Used to increase fluid density up to maximum of 14.0 ppg ±
Used as bridging agent in drill-in, oil and synthetic fluids
Lost Circulation Material
Material used to bridge off (seal) formations where whole mud is being lost to the formation
Nut shells (mostly pecan & walnut)
Mica
Fiber (wood, paper, plastic, etc.)
Formation solids
S.G. = 2.6 ±, Density = 21.67 ppg ±
Sand
Limestone
Dolomite
Soluble chemicals
Caustic Soda (NaOH)  pH 13.3
Caustic Potash (KOH)  pH 13.3
Lime [Ca(OH)2]  pH 12.4
Soda Ash (Na2CO3)  pH 11 - 11.5
Sodium Bicarb (NaHCO3)  pH 8.4
Zinc Oxide (ZnO)

Lignosulfonate (organic acid)
Spersene (chrome lignosulfonate)
Spersene CF (chrome-free lignosulfonate)
Chemical de-flocculant (mud thinner) adds anionic (negative) charges to the mud.
Lignite (organic acid)
Tannathin (lignite)
XP-20 (chrome lignite)
Chemical de-flocculant (mud thinner) adds anionic (negative) charges to the mud.
Neutralizes positive sites on the clays causing them to repel each other. 

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MUD RHEOLOGY

Rheology is the study of

how matter deforms and flows 

VISCOSITY

Resistance to flow of a fluid

FUNNEL VISCOSITY

• 100 centipoise (cp)  =  1 poise
• Centipoise is the dimension used to express:
• Plastic viscosity
• Apparent viscosity
• Effective viscosity

• The dimensions of lb/100 sq ft are used for expressing:

1. -Yield point
2. - Initial gel
3. - 10-minute gel

 SHEAR  STRESS

• Internal force that resists flow
• System pressure loss (circulating pressure on the rig)
• Simulated by the dial reading on a V G meter

SHEAR RATE

The velocity at which one layer of fluid moves past another

• The bulk (average) velocity at which a fluid is moving
• Annular velocity in the circulating system is an example of bulk velocity
• Velocity is the RPM on a V G meter

Viscosity

Factors Influenced by Mud Rheology

• Hole cleaning
• Suspension of solids
• Hole stability
• Solids control
• Equivalent circulating densities
• Surge / swab pressures 

Measurement - Rotational Viscometer

Effect of Temperature & Pressure

• Temperature reduces viscosity
• Pressure increases viscosity
• High temperature

1. Breakdown of polymers
2. Gelation of solids
   
   Plastic Viscosity
   
   

   • Resistance to flow due to mechanical frictio
   • Affected by:

   1. Solids concentration
   2. Size and shape of the solids
   3. Viscosity of the fluid phase

    Plastic Viscosity Increased by:
   
   

   Hydratable Drill Solids

   
   

   Clays, shales

   
   

   Inert Drill Solids

   
   

   Sand, limestone, etc.

   
   

   Colloidal Matter

   
   

   Starch, CMC

    

   Particles breaking, thus increasing surface area and more friction

   Weight material to increase density

    Area Increase by Breaking of Solids
   

   

    Effect of Particle Size on Viscosity
   
   

   

   
   

   

    Plastic Viscosity Decreased by

   Removal of Solids
   Shale shaker
   Desanders, desilters, and centrifuges
   Lowering of gel strength allows larger particles to settle out
   Dilution of solids with water

   How Solids Affect Mud Viscosity

   

   
   

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Basic Petroleum Geology and Log Analysis

Geology is the science that deals with the history and structure of the earth and its life
forms, especially as recorded in the rock record. A basic understanding of its concepts
and processes is essential in the petroleum industry, for it is used to predict where oil
accumulations might occur. It is the job of the petroleum geologist to use his/her
knowledge to reconstruct the geologic history of an area to determine whether the
formations are likely to contain petroleum reservoirs. It is also the job of the geologist to
determine whether the recovery and production of these hydrocarbons will be
commercially profitable.
The physical characteristics of a reservoir, how petroleum originated and in what type of
rock, what types of fluids exist in the reservoir, how hydrocarbons become trapped, and
basic well log analysis are some of the concepts vital to the production and recovery
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