The cost of drilling a water sensitive shale is reduced by first enhancing drilling rate by circulating a clear drilling fluid, then avoiding borehole instability due to shale-water interaction by circulating an aqueous solution of partially hydrolyzed polyacrylamide and alkali metal halide, and avoiding borehole instability due to mechanical incompetence of earth formations by circulating a suspension of pre-hydrated bentonite in the said solution to enhance the borehole cleaning while continui...

A barium sulfate scale or solid can be dissolved economically by flowing a stream of relatively dilute aqueous solution of aminopolyacetic acid salt chelating agent into contact with and along the surfaces of the scale while correlating the composition and flow rate of the solution so that each portion of solution contains an amount of chelant effective for dissolving barium sulfate and the upstream portions of the scale are contacted by portions of the solution which are unsaturated regarding t...

The dissolving of siliceous material in an environment containing corrodable metal and having a temperature exceeding about 300.degree. F. is improved by using an aqueous solution containing an amount of ammonium fluoride equivalent to that in a 2-3 molar solution of hydrogen fluoride and enough weak acid and weak acid salt to provide a pH of near to but less than 7.

The precipitation time of a plug forming aqueous solution of both a polyvalent metal that precipitates as a gelatinous metal hydroxide and a reactant that raises the pH to cause the precipitation, is controlled, at least in part, by a reaction between nitrite ions and urea.

Production is initiated from a gas well which is kept from producing by the hydrostatic pressure of the liquid it contains, by injecting an aqueous liquid that contains reactants which form nitrogen gas within the wall or reservoir and displaces enough liquid out of the well to lower the hydrostatic pressure to less than the fluid pressure in the adjacent portion of the reservoir and cause fluid to flow from the reservoir to the well.

A process for acidizing a subterranean region by contacting it with an acidic solution is improved by dissolving in the solution a pH-increasing reactant that subsequently adjusts the pH of the solution to a selected relatively neutral value.

A self-neutralizing aqueous acid comprising an aqueous solution of an acid and at least one pH-increasing material that reacts with water at a selected rate to yield ammonia or an amine to increase the pH of the solution to a selected value.

A thickened aqueous liquid, suitable for suspending packing particles, comprises an aqueous solution containing an acid-reactive cellulosic water thickening material, an acidifying material that causes the solution viscosity to decrease after a selected time-temperature exposure, and a relatively slowly reactive material that causes the solution pH to increase to a selected value after a longer time.

A backsurge of fluid through perforations in a well casing is chemically induced by injecting into the surrounding reservoir a solution which contains (a) nitrogen gas-generating reactants, (b) a reaction-retarding alkaline buffer, and (c) a pH-reducing reactant that is capable of subsequently overriding the buffer, so that a rapid production of gas and heat causes a backsurging of fluid into the wellbore.

A backsurge of fluid through perforations in a well casing is chemically induced by injecting into the surrounding reservoir a solution which contains (a) nitrogen gas-generating reactants, (b) a reaction-retarding alkaline buffer, and (c) a pH-reducing reactant that is capable of subsequently overriding the buffer, so that a rapid production of gas and heat causes a backsurging of fluid into the wellbore.