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), Journal Name: SPE (Society of Petroleum Engineers) Format. Eval.; (United States) Vol. 3:1; ISSN SFEVE
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALCOHOLS
ALKALINE EARTH METAL COMPOUNDS
ALKYLATED AROMATICS
AMMONIUM COMPOUNDS
AMMONIUM HYDROXIDES
AROMATICS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMICAL COMPOSITION
CLEANING
COMPARATIVE EVALUATIONS
CONTROL
DOLOMITE
DRILL CORES
DRILLING FLUIDS
FLUIDS
GEOLOGIC DEPOSITS
GEOPHYSICS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXIDES
HYDROXY COMPOUNDS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
METHANOL
MINERAL RESOURCES
MINERALS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
QUALITY CONTROL
REMOVAL
RESERVOIR ROCK
RESOURCES
ROCK-FLUID INTERACTIONS
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SOLVENTS
SURFACTANTS
TOLUENE
WETTABILITY