CO2-Toluene Whole Core Cleaner
The Model 920 CO2-Toluene Whole Core Cleaner is a system to clean crude oil, water, and drilling mud liquids from whole core samples in preparation for porosity and permeability measurements. The core is first saturated with CO2 and then with solvent (toluene) forcing the gas into solution. The cores are heated above the boiling point of water and when the pressure is reduced, the dissolved CO2 will drive the solvent and the core liquids from the rock pore space. The process was developed and patented in the 50's by Stanolind Oil Company, now know as Amoco Production Company. The development was an outgrowth of their pressure depletion gas drive production research.
The whole core cleaning system is constructed in two parts, the core cleaning cells and the fluid handling unit.
The cells are assembled and plumbed in pairs. The 12cm (4.75 inches) inside diameter cells are suitable for cores drilled in most of the world and a larger version, 15 cm (6 inch) diameter, primarily for cores drilled in the North Sea, is available. The standard length for both sizes is 236 cm
(93 inches) inside for an overall length of 2.4 m (8 feet). Steam jackets, common to each pair, provide the cell heating mechanism. As few as two and as many as eight cells can be mounted together and supplied by the Fluid Handling Unit. The cell skid comes plumbed complete with valves, gauges, and relief valves.
Fluid Handling Unit
The fluid handling equipment is all mounted on one skid. There are tanks for the clean and used solvent, and a solvent recovery still. The solvent recovery still consists of a stainless U-tube reboiler, liquid-gas disengagement area, and condenser. The still will recover about one gallon/minute.
A cyclone separator and water-cooled after-cooler are used to separate the hot solvent and CO2 returned from the cleaning cells when they are drained. An outside vent is required downstream from the after-cooler.
The fluid handling system is self-sufficient with the exception of having to replenish the clean solvent that is lost out the stack or through spillage.
The solvent recovery still is automatic. A process controller and an annunciator panel are enclosed in a NEMA-4 box, located outside of the hazardous environment. The system may be operated in automatic or manual mode. The process of filling the cells with CO2 and solvent, and draining is controlled by the process controller in automatic mode.
The system is operated in the follow manner. Trays are provided to hold the core in the cells.
1. Load all of the cells that are to be used.
2. On the control panel, select the NUMBER of pairs of cells that have been loaded (1,2,3,4).
3. Select the duration of the cleaning cycle SHORT (4 hours) or LONG (12 hours), and AUTOMATIC/START. The process controller operates the system by first opening the steam valve providing heat to the cell jackets.
Air is purged from the cells using CO2, then the cells are charged to about 1400 kPa (200 psi) with CO2. The cells are then filled, against a closed head, with solvent forcing the gas into solution and saturating the rocks. After a suitable soak time the cells are drained and the cycle repeated. At the end of the cleaning process, the cells are again drained and the steam that heats the cells is turned off.
Cell ID: 12 cm (4.75") ID is standard, 15 cm (6.0") ID is optional.
panel: NEMA-4 enclosure is standard,
explosion proof is optional. An
explosion proof room with ventilation that sweeps vapors from the floor is
recommended as a suitable enclosure. A floor drain with an 60-gallon minimum
capacity oil trap is also recommended.
CO2 in combination with toluene and at elevated temperature
is difficult to contain. Teflon seals
are used throughout to help minimize leaks.
The user supplies CO2, toluene, steam (a minimum of 45 kg at 240 kPa (100 pounds/hour at 35 psig)) regulated to 5-25 psig at the cell steam jackets and 35-40 psig at the recovery still, cooling water (40 l/m at 140 kPa (5 gpm @ 20 psi) minimum), and 230-volt, single phase, 5-amp service.