Dissolving siliceous materials with self-acidifying liquid

Claim 2

The process of claim 2 in which a slug of an aqueous acid that is substantially free of hydrofluoric acid and is adapted to dissolve multivalent metal carbonates is flowed into the well ahead of said liquid mixture.

Claim 3

The process of claim 2 in which a relatively dilute aqueous acid that is substantially free of hydrofluoric acid and is capable of dissolving ralstonite is flowed into the well behind said liquid system.

Claim 4

The process of claim 2 in which: a slug of aqueous acid that is substantially free of hydrofluoric acid and is adapted to dissolve both calcium carbonate and ralstonite is injected ahead of said liquid system in a volume sufficient to dissolve carbonates encountered in the reservoir and leave substantially unspent acid; and after injecting said liquid system into the reservoir and allowing it to react, fluid is backflowed from the reservoir until at least a portion of a region contacted by the liquid system is swept by backflowing, unreacted portions of said first-injected slug of acid.

Claim 5

The process of claim 2 in which said liquid system is flowed into contact with siliceous material by positioning a slug of said liquid system in a casing, perforating the casing, and displacing liquid through at least one perforation and into a subterranean reservoir.

Claim 6

The process of claim 2 in which said liquid system is thickened by the addition of an aqueous thickening agent and the thickened liquid system is utilized as a carrier liquid for a pack-forming slurry of sand or gravel from which the carrier liquid is subsequently displaced into eArth formations around the well.

Claim 7

The process of claim 1 in which the water-reactive organic ester is an ester of a water-soluble fatty acid.

Claim 8

The process of claim 8 in which said ester is a water-soluble alcohol ester.

Claim 9

The process of claim 1 in which the water-reactive organic acid ester is methyl formate.

Claim 10

The process of claim 1 in which the fluoride salt is ammonium salt of hydrofluoric acid.

Claim 11

The process of claim 1 in which: the location of the siliceous material to be dissolved is such that fluid being flowed nto contact with it must pass through a structure or region that is susceptible to attack by acid; and the composition of said liquid system and the rate of said flowing of it are adjusted so that said liquid system is substantially neutral while it passes through said region of acid susceptibility.

Claim 12

The process of claim 1 in which said aqueous liquid is water at least substantially as pure as fresh water, said fluoride salt is an ammonium salt of hydrofluoric acid and said ester is methyl formate.

Claim 13

A process for dissolving a siliceous material in a remote location into which a fluid can be flowed which process comprises: mixing (a) at least one aqueous liquid (b) at least one water-soluble fluoride salt and (c) at least on relatively slowly reactive acid-yielding material that yields an acid adapted to convert an aqueous solution of said fluoride salt to an aqueous solution of hydrofluoric acid, to form a substantially homogeneous system in which the components interact to provide an aqueous solution that contains enough hydrofluoric acid to dissolve bentonite while having a pH of at least about 2; flowing said liquid system into contact with siliceous material to be dissolved; and adjusting the composition of said liquid system and the rate of flowing it so that the siliceous material is contacted by the system while the bentonite-dissolving proportion of hydrofluoric acid is present in the aqueous solution.

Claim 14

The process of claim 14 in which the siliceous material to be dissolved is located in or around the borehole of a well.

Claim 15

The process of claim 14 in which the composition of said liquid system and the rate of flowing it are adjusted so that unreacted water-soluble fluoride salt remains in the aqueous solution while the solution is in a region in which it is desired to maintain a relatively high pH.

Claim 16

The process of claim 14 in which the acid-yielding material is an ester of a water-soluble fatty acid.

Claim 17

The process of claim 14 in which the acid-yielding material is a hydrolyzable organic halide.

Claim 18

The process of claim 14 in which the acid-yielding material is an acyl halide.

Claim 19

The process of claim 14 in which the acid-yielding material is an acid anhydride.