Abstract: The crosslinking of galactomannan gum fracturing fluids by borate ion is delayed for high temperature applications by completing boron in a basic solution with an organic polyol. Low pumping friction pressures are achieved by the delay in the crosslinking with the boron being available at high temperatures to add high temperature stability to the fracturing fluid at temperatures ranging upto about 300.degree. F.

Abstract: To reduce the production of water from a subsurface hydrocarbon-bearing interval of a formation the producing interval of the formation is treated with an aqueous solution or sol of a high molecular weight, water soluble polyacrylamide (PAM). The polymer which is absorbed in the formation is crosslinked in situ, e.g. by subsequently flushing the formation with a crosslinking solution.

Abstract: A method of well completion is provided which enables much of the well casing to be later recovered from the well in the event the well is later abandoned, or where intermediate casing must be run during drilling of the well but may later be removed when the liner is in place. The well is completed by any of several embodiments of manipulative steps, leaving the lower portion of the annulus filled with a conventional cementitious material and the upper portion of the annulus filled with an aqueous gel comprising effective quantities of water, a water soluble alkali metal silicate, and a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate. An economically significant portion of the casing can thereafter be recovered if necessary after first severing the casing above that portion adjacent the set cementitious material.

Abstract: Fluid loss control for aqueous chemical washes of the type used in well cementing is provided by incorporating in the wash, an effective amount of an oil-soluble resin mixture comprising a particulate friable resin and a particulate pliable resin.

Abstract: Fluid loss control for aqueous chemical washes of the type used in well cementing is provided by incorporating in the wash, an effective amount of the oil-soluble resin mixture described in U.S. Pat. No. 3,891,566.

Abstract: As an aqueous fracturing fluid is pumped into a well bore penetrating a subterranean formation a galactomannan gum, a buffer which promotes an initial acidic pH in the fluid, a borate ion releasing compound and a compound which functions to shift the pH of the fluid to the basic side after a certain short period of time are dispersed into the fluid. The resulting viscous fracturing fluid is employed to fracture a subterranean formation to, for example, stimulate the flow of fluids therefrom.

Abstract: Viscous aqueous solutions are prepared which maintain a certain viscosity range over a predetermined period of time (i.e., induction period) and which thereafter break, i.e., decrease in viscosity over a very short period of time. The viscous aqueous solution comprises a polysaccharide having an ability to thicken water and dispersed or dissolved in the aqueous solution an effective quantity of an organic ester which, at a temperature at which it is desired to break the viscous solution, hydrolyzes over a delayed period of time to form an acid which degrades the polysaccharide, thus causing a splitting of the polysaccharide chain and a decrease in the viscosity of the solution.