Abstract: A 9 to 12 ppg (1.08 to 1.4 kg/liter) cement slurry for use in oil well type completions which comprises hydraulic cement about 10 to about 30 weight percent hollow glass microspheres based on the weight of the cement and sufficient water to form a pumpable slurry with an API free water content of no more than about 2 volume percent. This slurry is preferably mixed with an amount of water required to produce a slurry with the hydraulic cement having at least an API minimum water content and an API free water content of no more than about 2 volume percent and an additional amount of water equal to about 1.3 to about 1.8 weight percent water based on the weight of the hydraulic cement for each weight percent of the microspheres. The microspheres have true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.

Abstract: In the production of xanthan gum by action of Xanthomonas bacteria on a nutrient medium, the yield of xanthan gum can be improved by the addition of deoxycholate or cholate to the nutrient medium at the time of inoculation of the bacteria on the nutrient medium.

Abstract: A sample of a subterranean formation is prepared for NMR analysis by saturating the sample with an aqueous liquid and then immediately immersing it in a liquid halocarbon. An NMR analysis is conducted on the immersed sample. The liquid halocarbon does not have hydrogen atoms bound thereto which would interfere with the NMR analysis and preferably has a sufficient viscosity to substantially eliminate the displacement of aqueous liquid from the sample. The sample can be stored in the liquid halocarbon for maintaining aqueous liquid within the sample.

Abstract: This invention relates to a method of determining oil saturation in an underground rock formation penetrated by a wellbore by use of a log-inject-log technique. In such techniques, thermal neutron decay time logs are taken with the formation in the native state and then again after fresh water has been injected into the formation. These logs determine water saturations which are used to determine oil saturation. The method of this invention is directed to a method to prepare an aqueous salt solution so that clay and shale impairment of the formation is prevented but such that the thermal neutron capture cross section of the injected fresh water is not significantly different from that of the fresh water typically used.

Abstract: Highly conductive subterranean zones are treated with aqueous fluids containing gel-forming amounts of water-soluble lignosulfonate and silicate. Suitable treating fluids contain about 2 to about 5 weight percent sodium or ammonium lignosulfonate and sodium silicate at a weight ratio of SiO.sub.2 to lignosulfonate of about 0.2 to about 1.

Abstract: A well which is to produce from a heavy oil or tar sands reservoir is thermally stimulated from another well located on the order of 10 to 50 feet away. This adjacent thermal stimulation well can be considered expendable. This thermal stimulation is continued for a number of days, until the hot zone produced extends beyond the location of the production well. Thereafter, the adjacent thermal stimulation well preferably is closed off during the course of the frontal thermal drive or the like from remote injection wells. However, such stimulation may be repeated later of if the oil or tar becomes too viscous in the pay zone near the production well.

Abstract: A viscoelastic polymer such as polyacrylamide is first prehydrated in an aqueous fluid having a low degree of hardness and the prehydrated viscoelastic polymer solution is mixed with hard brine to provide a polymer bank with improved mobility control. This improved mobility control is obtained by mixing the hard brine with the prehydrated viscoelastic polymer at high volume ratios of hard brine to the polymer.

Abstract: Highly conductive zones in subterranean formations are treated with aqueous fluids containing gel-forming amounts of water-soluble lignosulfonate and silicate. Suitable treating fluids contain about 2 to about 5 weight percent sodium or ammonium lignosulfonate and sodium silicate at a weight ratio of SiO.sub.2 to lignosulfonate of about 0.2 to about 1.

Abstract: Gravity gradiometer including a ring laser cavity, two modulator elements in the path of the laser beam, and spaced masses attached to the modulator elements to provide a differential modulation of circular polarization modes proportional to the difference in gravity at the location of the two masses. In one form, a biasing element is added to shift the operating point of the laser system to improve performance.

Abstract: A 9 to 12 ppg (1.08 to 1.4 kg/liter) cement slurry for use in oil well type completions which comprises hydraulic cement about 10 to about 30 weight percent hollow glass microspheres based on the weight of the cement and sufficient water to form a pumpable slurry with an API free water content of no more than about 2 volume percent. This slurry is preferably mixed with an amount of water required to produce a slurry with the hydraulic cement having at least an API minimum water content and an API free water content of no more than about 2 volume percent and an additional amount of water equal to about 1.3 to about 1.8 weight percent water based on the weight of the hydraulic cement for each weight percent of the microspheres. The microspheres have true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.

Abstract: Micellar crude oil displacement efficiency is improved by partitioning the hydrocarbon sulfonate surfactants used in the formulation of micellar fluids between aqueous and oleic phases of a separation liquid and using the portion which is partitioned into the oleic phase in the formulation of the micellar fluid.

Abstract: An improved method for reducing fluid loss during high pressure hydraulic fracturing of well formations using an aqueous foam involving adding to the foam from about 0.0005 to 0.5% by weight of an additive selected from the group consisting of a C.sub.5 to C.sub.10 unsubstituted monocarboxylic aliphatic acid, a C.sub.5 to C.sub.10 unsubstituted aliphatic alcohol, malonic acid, lower n-alkyl diesters of malonic acid and their mixtures. The new additives are shown to be as effective in reducing fluid loss during fracturing as the commercial practice employing hydroxy ethyl cellulose at a fraction of the cost of hydroxy ethyl cellulose without depositing polymer within the formation.

Abstract: A method for improving the sweep efficiency of a waterflood comprising the addition of a small amount of a surfactant, preferably a petroleum-derived sulfonate, to at least the first portion of injected water. The surfactant interacts with clays in the formation to reduce the permeability of the formation to the flood water and thereby improve the mobility ratio of the flooding process, resulting in a better sweep efficiency of the flooding medium through the reservoir.

Abstract: A simplified method for tensioning casing in thermal wells involving the use of an inflatable packer element. The packer element is positioned at or near the bottom of a casing string and is inflated with cement after the cement annulus has been filled with cement. The packer is used to anchor the bottom of the casing while tension is applied to the top of the casing during the setting of the cement. After the cement has set the packer is a permanently imbedded in the casing cement.

Abstract: The present invention relates to a crosslinked aqueous gel for fracturing and placing propping agents within subterranean formations, said gel having a viscosity in said formations greater than about 20,000 centipoises and having pumping characteristics in turbulent flow approaching those of water.

Abstract: A method of selective plugging of undesirable high permeability streaks and channels in oil-bearing reservoirs during high temperature (250.degree. F. or higher) injection recovery processes such as steamflooding, underground combustion, flooding of a naturally occurring high-temperature reservoir or the like. Improved sweep efficiency can be effected by injecting a gel-forming solution consisting essentially of sodium or ammonium lignosulfonate and water or brine in the absence of other gelation promoters and then allowing the high temperatures of the underground formation to promote gelation. Optionally, a precooling water injection step can be used prior to placement of the gel-forming solution. This system has the advantage of gel times which are sufficiently long at temperatures in excess of 250.degree. F. to permit placement of large volumes characteristic of commercial use. This method is particularly useful in selectively forming firm, strong gels in thief zones for steamflooding recovery operations.