Oil Mud Properties

Mud weight of oil muds ranges from 7.5 lb/gal to over 22.0 lb/gal. Downhole density is affected by temperature and pressure more than water base muds. Temperature will decrease the density of oil muds due to expansion and pressure will increase the density due to compression of the oil phase.

Viscosity is affected by temperature and pressure. As the temperature increases, viscosity decreases. Conversely, as the pressure increases, the viscosity increases. The funnel viscosity measurement of an oil mud is greatly affected by temperature. The funnel viscosity of an oil mud is usually used an indicator and is not normally used for treatment purposes. Rheological properties are usually made with a rotational viscometer. The plastic viscosity, yield point and gel strengths measurements (according to the Pseudoplastic Rheology Model) are made with the rheometer. More accurate descriptions of the rheology of the mud are made with the Yield-Power Law Model. Suspension of cuttings and weighting material is monitored with the gel strength (for static settling) and 3 or 6 rpm reading (for dynamic settling). Run the rheology of oil muds at the same temperature for each test. Plastic viscosity is greatly affected by temperature at which mud is normally tested. The higher the temperature the lower the plastic viscosity. Reduce plastic viscosity by solids control or dilute with base oil. Yield point is somewhat affected at temperatures where mud is normally tested but may be greatly affected by temperatures above 350°F. Increase yield point by additions of organophilic clay, oil polymers or water. Decrease with wetting agents or thinners or dilution with base oil. Gel strengths behaves similar to yield point. Increase with organophilic clay, water or rheological modifiers. Decrease with wetting agents or thinners or even dilution with base oil.

Electrical stability (E.S.) is the increase in voltage across a probe until the emulsion breaks and a current is established. The electrical stability will vary with the amount of water - the more water generally the lower the stability. Presence of conductive solids such as hematite and insoluble salt will result in low E.S. readings. New sine wave E.S. meters are more reproducible and reliable. The readings from these meters are about one-half the value of the previous meters. Falling E.S. readings and the presence of water in the filtrate indicate weakening of the emulsion. Emulsifiers and lime additions are usually required.

HPHT filtration is run at bottom hole temperatures under static conditions to determine condition of emulsion, the filtrate volume and filter cake quality. If water is present in the filtrate, this could indicate emulsion weakening. Thick filter cakes and high fluid loss indicate excessive drill solids content. Lower the filtration rate with filtration control agents, emulsifiers and lime. Increase the fluid loss by dilution with base oil.

Salinity determination of calcium and sodium chloride is done on the whole mud. A new method for this test is now established by the API to determine types of salts present and if any salt is insoluble in the mud. Insoluble calcium chloride can cause water wetting problems and should be reduced by adding water or oil mud with no salinity in the water phase. Insoluble sodium chloride can be reduced in the same manner, but it does not cause water wetting of solids.

Lime analysis determines the amount of excess lime in the oil mud. Lime is essential for the formation of the emulsion when using fatty acid type emulsifiers. Lime content should always be checked since emulsifier additions may not be required due to deficiency in the lime content. A decrease in lime content while drilling may indicate acid gases such as H2S or CO2 or high temperature deterioration of products.

Water Activity or relative humidity of the oil mud is determined with a hygrometer. The hygrometer does not determine if any insoluble salt is present.

Oil/Water/Solids ratio in the oil mud is determined with a retort, which is a still that operates at about 650oF. Results need to be accurate, especially for the salinity analysis. Small sources of error in water content can cause large differences in salinity analysis.

Sulfides in the oil mud are measured with the Garrett gas train. A sample of whole mud is used instead of filtrate. Zinc oxide is the preferred compound to treat for soluble sulfides. Increased lime additions are also necessary when H2S is present.

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Responses

  • Fosco Brandagamba
    What is the principle of measuring emulsion stability in a oil base mud?
    9 years ago
  • fulvus
    How does temperature affect yield point of a drilling fluid?
    8 years ago
  • biniam
    Can the ph of an oil base mud be measured?
    8 years ago
  • Milena
    How accurate is a hygrometer in drilling fluids applications?
    7 years ago
  • szymon
    Is a retort more accurate with lower solids muds?
    7 years ago
  • Leigh
    What is density of base mud?
    7 years ago
  • pio
    What function does calcium chloride have in oil base mud?
    7 years ago
  • malachy donaldson
    What mud properties are determined using a rheometer?
    6 years ago
  • vala
    What is excess lime in oil base mud does?
    5 years ago
  • massawa
    What is whole mud chlorides drilling?
    5 years ago
  • ahti
    Does mud affect water temperature?
    4 years ago
  • haylom
    What temperature is mud when testing yield point?
    3 years ago
  • Prudenzio
    Are high chlorides desirable in drilling mud?
    3 years ago
  • Tilly
    How does Increase in density affect drilling of fluids?
    3 years ago
  • MEERI
    How do you control high plastic viscosity?
    2 years ago
  • lyyli
    What is the effect of high plastic viscosity in oil well?
    2 years ago
  • Ermias
    How has plastic viscosity affect the drilling operation in resent years?
    2 years ago
  • TANTA
    How does viscosity and density affect drilling mud?
    2 years ago
  • Sophie
    How does mud density relative with apparent vicosity in drilling mud?
    2 years ago
  • glen
    What is the effect of increasing the water phase salinity of OBM?
    2 years ago
  • IGINO CREMONESI
    How to increase mud yield point?
    2 years ago
  • mimosa
    What is the normal ph of an oil base mud?
    1 year ago
  • vihtori
    How to reduce excess apparent viscosity in drilling mud?
    1 year ago
  • nea
    How to calculate excess lime in Oil Base mud?
    1 year ago
  • ayaan
    How does temperature affect the density of drilling fluids?
    1 year ago
  • Hilda
    HOW TO LOWER DENSITY ON A MUD?
    1 year ago
  • brody hunter
    What steps to reduce HTHP in oil base drilling fluids?
    1 year ago
  • obo sandyman
    Does temperature effect mud weight downhole?
    1 year ago
  • Eleuterio
    Why does water increase rheology in OBM?
    1 year ago
  • Ghenet
    What is the difference in treated oil base mud and base oil base mud?
    12 months ago
  • armaan
    How does effect oil base mud?
    11 months ago
  • arvid
    How to test relative humidity in oil base mud?
    11 months ago
  • robert
    Does mud weight effect gas readings?
    10 months ago
  • FIYORI
    What are the effects of viscosity on drilling fluids?
    8 months ago
  • KIROS DEMSAS
    Does yield point increase or decrease with temperature?
    8 months ago
  • swen
    How to lower the yeild point of oil base mud?
    7 months ago
  • lioba
    How does viscoity effect drilling fluids?
    7 months ago
  • bernd
    What is oil based mud properties?
    7 months ago
  • Wallace
    How to reduce plastic viscosity drilling?
    7 months ago
  • benilde
    Does oil base mud get aired up?
    6 months ago
  • merigo
    How high mud weight effect to gas show in drilling?
    6 months ago
  • camelia
    How to increase weight in oil based mud?
    5 months ago
  • nikki
    Why is my yeild point high in obm?
    4 months ago
  • PRIAMUS
    What effect does raising temperature have on mud weight?
    4 months ago
  • Erminia
    What is a good plastic viscosty for oil based mud?
    4 months ago
  • dawit berhane
    What products in oil base mud gives you yield point?
    3 months ago
  • brooke alexander
    How to increase emulsion stability in drilling mud?
    2 months ago
  • rocco
    Is increasing the mud weight when drilling for oil good?
    2 months ago
  • Ulrich
    What is the name of the fluid weight downhole oil?
    2 months ago
  • Joann
    How does lime effect oil base mud?
    1 month ago
  • Leon
    What does 6RPM mean on oil base mud checks?
    23 days ago

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