| The purpose of extraction and drying is to obtain samples that are free of hydrocarbons, water and soluble salts that are suitable for further analysis. To select the appropriate extraction and drying technique that matches the sample mineralogy and study objectives, we use hot shot XRD/SEM which gives us valuable information on the sample mineralogy within a short timeframe. |
 Water, oil and salts are extracted from plugs using a soxhlet apparatus and organic solvents. The choice of organic solvent(s) depends on the material to be extracted. Organic solvents such as toluene, methanol or an azeotropic mixture of chloroform, methanol and water are available.
The duration of soxhlet extractions of plugs can vary from several days (for coarse grained or porous materials) to weeks (for fine grained or dense materials). Completion of the extraction is determined by checking the cleaning liquid for salt content and by ultraviolet fluorescence scanning of the plugs. |
| This is a gentle and fast method for the removal of hydrocarbons (heavy, waxy or asphaltic crudes) and formation water salts from core plugs. Cylindrical core samples are individually loaded into core holders. Series of miscible solvents are then flowed through the samples. Low flow rates, not exceeding realistic reservoir conditions, are used to prevent sample damage through clay migration. From the measured flow rate and the pressure differential an estimation of the liquid permeability of a sample can be derived in an early stage of the core analysis project. |
| After soxhlet extraction, samples are dried to constant weight. Most commonly a hot oven is used for samples that are free of sensitive clays. A humidity-controlled oven is commonly used for samples containing gypsum, clay and/or shales. |
| When minerals are present that are sensitive to fluid phase changes (e.g. illite), critical point drying can be considered. Normal drying techniques create a large surface tension across the gas-liquid interfaces, which can cause fibrous illites to deform and hence alter the permeability of the rock. Critical-point drying will prevent the collapse of illites because the illite will never be exposed to high gas-liquid surface tensions. |
