Abstract: A method and logger apparatus for analyzing mud returns to determine the presence of formation hydrocarbons. The logger takes a gas sample from a gas trap formed in the mud return line, purges it of all non-helium gases either by condensing them or chemically reacting them out of the sample. The sample is then fed into a special helium mass spectrometer that identifies how much of each helium isotope (.sup.3 He and .sup.4 He) is present. This data is then fed to a correlator/computer and an isotope ratio calculated and monitored. A significant increase in this ratio is indicative of the presence of formation hydrocarbons. The computer uses additional input to track the sample vs its original downhole location to enable proper identification. The method and apparatus are particularly useful with oil-based drilling fluids.

Abstract: Filterability of aqueous solutions of polymers employed to thicken waterfloods such as biopolymers (e.g. heteropolysaccharides) is improved by addition of a surfactant (e.g. a sulfated alkoxylated alcohol). Filterability is further enhanced by addition of an ethoxylated alcohol surfactant and/or an alcohol.

Abstract: A sidestream of injection liquid taken downstream of a filter is passed through a monitoring filter of appropriate pore size. Pressure drop over the monitoring filter is determined and a regeneration cycle for the main filter is triggered in response to differential pressure (.DELTA.P) over a preset value, which corresponds to deterioration in filtrate quality.

Abstract: Wireline apparatus and method for measuring pressure downhole in well tubing comprising a main plug body which seats in a seating nipple forming part of the tubing, a pressure gauge in communication with the tubing below the main plug body, and means for equalizing the tubing pressure above and below the seated main plug body so that the apparatus may be removed from the well.