Core cleaning for restoration of native wettability
Certain additives used in drilling and completion fluids may alter the wettability of core. For example, the surfactants in invert-oil-emulsion drilling muds are known to alter the wettability of core. Because routine cleaning methods do not remove these surfactants, core that is to be used for special laboratory analyses, such as relative permeability, capillary pressure, and saturation exponent, is left with an altered wettability. Experiments with such core will obviously produce erroneous data. To obtain reliable results, cleaning methods must be developed to remove these surfactants, allowing restoration of plugs to their natural wettability. Once the core is cleaned, the wettability of the cleaned core can be restored by saturating with synthetic formation brine and uncontaminated reservoir crude, then aging at the reservoir temperature. This report ranks the efficiency of solvents in removing surfactants from plugs contaminated with invert-oil-emulsion drilling-mud filtrate. Eight solvents for Berea sandstone and seven solvents for Guelph dolomite have been ranked after Dean-Stark extraction of mud surfactants using the U.S. Bureau of Mines (USBM) wettability index. The best solvent for both rock types was a 50/50 mixture of toluene/methanol, or the equivalent, containing 1% ammonium hydroxide. Toluene, the most commonly used solvent for core cleaning, was one of the poorest solvents tested. The solvents that are effective in removing surfactants can be used to clean contaminated core.
- Research Organization:
- Conoco Inc. (US)
- OSTI ID:
- 6983439
- Journal Information:
- SPE (Society of Petroleum Engineers) Format. Eval.; (United States), Vol. 3:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DRILL CORES
CLEANING
QUALITY CONTROL
WETTABILITY
SURFACTANTS
REMOVAL
AMMONIUM HYDROXIDES
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
DOLOMITE
DRILLING FLUIDS
GEOPHYSICS
METHANOL
PETROLEUM DEPOSITS
RESERVOIR ROCK
ROCK-FLUID INTERACTIONS
SANDSTONES
SOLVENTS
TOLUENE
ALCOHOLS
ALKALINE EARTH METAL COMPOUNDS
ALKYLATED AROMATICS
AMMONIUM COMPOUNDS
AROMATICS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CONTROL
FLUIDS
GEOLOGIC DEPOSITS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXIDES
HYDROXY COMPOUNDS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERAL RESOURCES
MINERALS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
RESOURCES
ROCKS
SEDIMENTARY ROCKS
020200* - Petroleum- Reserves
Geology
& Exploration