Abstract: A method using computerized axial tomography (CAT) to model flood performance in a petroleum reservoir using model rock or core from the reservoir of interest. The method uses X-rays of two different energy levels and dopes one of the fluids in the core with a strong photoelectric absorbing material. Multiple scans are conducted at the two energy levels during the displacement process. The resulting data permits calculation of the oil, water and gas phase saturations.

Abstract: A method for use with a computerized axial tomographic scanner (CAT) of providing an image of a sample that has spatial resolution in the axial direction that is smaller than the width of the X-ray beam of the CAT. The sample is scanned at a plurality of points in a plurality of cross sections that are separated by a distance that is less than the width of the X-ray beam of the CAT to determine the measured density function for each of the plurality of points. The measured density function is deconvolved with the beam width function for the CAT for each of the plurality of points to obtain the actual density function for the plurality of points. The actual density function is then used to generate an image of the sample that has a spatial resolution in the axial direction that is smaller than the width of the X-ray beam of the CAT.

Abstract: An apparatus for providing data for the calibration of the atomic number and density of a test material being scanned in the radiation field of a computerized axial tomographic scanner (CAT). The apparatus comprises a housing which is adapted to be positioned in the X-ray field of the CAT in a predetermined position. The housing has an aperture that is adapted to accommodate the test material, and a plurality of calibration materials which have known atomic numbers and densities are positioned in the housing. In addition, the present invention provides a calibration apparatus that has a surface that is adapted to accommodate the test material.

Abstract: An apparatus is provided for positioning a sample in the radiation field of a computerized axial tomographic scanner (CAT) for scanning by the CAT. The apparatus has a first support on a first side of the CAT and a second support on a second side of the CAT opposite the first side of the CAT. Both supports have respective guides and respective trolleys mounted upon their guides. The trolley on the first support is coupled to the second trolley by a suitable coupling so that movement of the first trolley by its motor causes similar movement of the second trolley, and the coupling with a sample mounted thereon passes through the radiation field of the CAT. A controller controls the motor to correctly position the sample as determined by a sample position sensor.

Abstract: A method of obtaining an atomic number image of an unknown material. A plurality of calibration materials which have a plurality of different known atomic numbers and densities are scanned with a CAT at first and second energies to determine the attenuation coefficients for the plurality of calibration materials at these energies. The energy-dependent coefficients at the first and second energies are determined from the attenuation coefficients for the plurality of calibration materials at the first and second energies according to a predetermined relation. The unknown material is scanned with a CAT at the first and second energies to determine the attenuation coefficients at a plurality of points in a cross section of the unknown material at these energies. The determined energy-dependent coefficients and the determined attenuation coefficients for the unknown material at the first and second energies are used to determine an atomic number image for the unknown material.

Abstract: A method of correlating a core sample with its original position in a borehole. The borehole is logged to determine the bulk density of the formation surrounding the borehole. The core sample is scanned with a computerized axial tomographic scanner (CAT) to determine the attenuation coefficients at a plurality of points in a plurality of cross sections along the core sample. The bulk density log is then compared with the attenuation coefficients to determine the position to which the core sample correlates in the borehole. Alternatively, the borehole can be logged to determine the photoelectric absorption of the formation surrounding the borehole, and this log can be compared with data derived from scanning the core sample with a CAT at two different energy levels.

Abstract: A method of determining the invasion of drilling fluid into a core sample taken from a borehole. A first material is added to the drilling fluid to obtain a first fluid that has an effective atomic number that is different than the effective atomic number of the connate fluids in the rock formation surrounding the borehole. A preserved core sample is collected from the borehole for scanning by a computerized axial tomographic scanner (CAT) to determine the attenuation coefficients at a plurality of points in a cross section of the core sample. The preserved core sample is scanned with a CAT at first and second energies, and the determined attenuation coefficients for the plurality of points in the cross section at each energy are used to determine an atomic number image for the cross section of the core sample. The depth of invasion of the first fluid is then determined from the atomic number image, as an indication of the depth of invasion of the drilling fluid into the core sample.

Abstract: Oil is displaced within a subterranean reservoir by injecting a combination of substantially liquefied CO.sub.2, brine and surfactant material into the reservoir, with the surfactant material being a polyalkoxy aliphatic sulfonate surfactant material which has specified dispersing and partitioning properties in contact with the brine and the fluids in the reservoir at the reservoir temperature and a pressure sufficient to substantially liquefy the CO.sub.2 within the reservoir.

Abstract: An oil recovery process that utilizes an injection of CO.sub.2, surfactant and water is improved by using a selected polyalkoxylated alcoholic or phenolic surfactant which is capable of forming three particular types of dispersions with the fluids in the reservoir at the reservoir conditions which are maintained during the process.

Abstract: In an oil recovery process in which an aqueous solution thickened with a water-soluble anionic polysaccharide polymer (Xanthan gum polymer) is injected into a subterranean reservoir, the stability of the solution viscosity is improved by de-oxygenating the aqueous liquid and then adding a sulfur-containing antioxidant, a readily oxidizable water-soluble alcohol or glycol and the Xanthan gum polymer.

Abstract: An aqueous xanthan gum polymer solution that contains bacterial cell bodies can be clarified by enzymatically disintegrating the cell bodies and/or filtering the solution to remove suspended solids. The clarification is improved by initiating an enzymatic disintegration but, before the cell bodies are completely disintegrated, contacting the solution with particles of solid siliceous material at an adsorption-enhancing pH, and then filtering-out the siliceous solids and the partially-disintegrated cell bodies that are adsorbed on them.