Viscoelastic compositions suitable for use as diversion agents in a process for acidizing a carbonate-based subterranean oilfield formation are disclosed. The compositions comprise water, a tall oil fatty acid (TOFA)-based amidoamine betaine, a C.sub.1-C.sub.4 alcohol, and propylene glycol. The invention includes an acidizing process that utilizes a mineral acid and an effective amount of the viscoelastic composition. The viscoelastic compositions effectively divert acid flow, thereby optimizing acid utilization and minimizing acid spend. The compositions fully develop formations, stabilize and/or promote formation of worm-like micelles, and maintain a high, stable viscosity during an acidizing process. Surprisingly, the compositions perform well at low surfactant does, high pressures, and temperatures greater than 350° F. The compositions can tolerate higher levels of corrosion inhibitors than known alternatives and can be used in formations having ferric ion contents greater than 10,000 ppm.

Systems and methods for predicting and optimizing the effects of acidizing treatment of carbonate rock are disclosed. The disclosed methods predict the conflicting effects of increased production (i.e., wormhole creation) and reduced rock compressive strength due to acid rock reactions. The mechanical stability of stimulated wellbores, such as horizontal wellbores, can be determined under different acidizing conditions, such as acid type and volume. The acidizing conditions can be optimized to maximize short and long-term production.

An object of the present invention is to provide a salt water thickener that uniformly (favorably) disperses ultrafine cellulose fibers even in a liquid containing a salt (electrolyte). The salt water thickener comprises ultrafine cellulose fibers and a water-soluble polymer and can thereby uniformly disperse the ultrafine cellulose fibers even in a liquid containing a salt. The salt water thickener of the present invention is uniformly dispersed even in a liquid containing a salt and therefore exerts a high viscosity. The salt water thickener of the present invention can also be used as an additive for a fluid. The salt water thickener of the present invention can be used for purposes, for example, subterranean formation processing.

Described herein are methods and techniques for deep reservoir stimulation of a hydrocarbon-containing subsurface formation. The methods may comprise introducing or injecting a formation-dissolving fluid, such as a wet acid-forming gas, into the subsurface formation; allowing the formation-dissolving fluid, such as the wet acid-forming gas, to react with the subsurface formation for a period of time; and producing hydrocarbons from the subsurface formation.

A novel method for the placement of spearhead acid and stimulation of a hydrocarbon-bearing formation, said method comprising the steps of providing a wellbore in need of multiple stages of stimulation; inserting an isolation plug in the wellbore at a predetermined location; inserting a perforating tool and a spearhead or breakdown acid into the wellbore simultaneously exposing the wireline and tool to the acid; positioning the tool at said predetermined location; perforating the wellbore with the tool thereby creating a perforated area; allowing the spearhead acid to come into contact with the perforated area for a predetermined period of time sufficient to prepare the formation for stimulation; removing the tool form the wellbore; and initiating the stimulation of the perforated area using a stimulation fluid. Also disclosed is a corrosion inhibiting composition for us with the acid composition.

Methods for mining soluble minerals from a subterranean deposit. A fluid is injected into a horizontal injection wellbore passing through the deposit and allowed to enter a mining/fracture plane having at least one fracture, extending from the horizontal injection wellbore, at a pressure sufficient to further fracture the deposit, maintain the mining/fracture plane or open the mining/fracture plane. The injected fluid is allowed to dissolve some of the soluble minerals from the deposit thereby forming a mineral solution which is produced from horizontal production wellbores that intersect the mining/fracture plane.

The disclosure provides methods and systems for recovering a target mineral from a mineral-bearing deposit. One or more first wells and one or more second wells are drilled into the deposit, each well having a substantially vertical section and a substantially horizontal section, the horizontal section of the second wells located above the horizontal section of the first wells. At least one channel from the horizontal section of each first well toward the horizontal section of the second wells is established. A fluid is injected into the deposit from the horizontal section of the first wells to form one or more slots. A brine is recovered from the horizontal section of the second wells, forming a cavity. A salt solution is then injected into the cavity from the horizontal section of the second wells and a target mineral-enriched solvent is recovered from the first wells.

A novel method for the placement of spearhead acid and stimulation of a hydrocarbon-bearing formation, said method comprising the steps of: providing a wellbore in need of multiple stages of stimulation; inserting an isolation plug in the wellbore at a predetermined location; inserting a perforating tool and a spearhead or breakdown acid into the wellbore simultaneously exposing the wireline and tool to the acid; positioning the tool at said predetermined location; perforating the wellbore with the tool thereby creating a perforated area; allowing the spearhead acid to come into contact with the perforated area for a predetermined period of time sufficient to prepare the formation for stimulation; removing the tool form the wellbore; and initiating the stimulation of the perforated area using a stimulation fluid.

Reducing leak-off during acid stimulation with dissolvable material sized to preferentially block crevices and wormholes, thus allowing the acid to travel further down the fractures, etching deeper into the reservoir than a similar process not using such dissolvable materials. After stimulation, the materials dissolve and production can proceed and will be improved over what is possible without such dissolvable materials.

A system and method for hydraulic fracturing including mixing seawater with an additive to precipitate sulfate from the seawater and mixing a flocculating agent with the seawater to agglomerate the sulfate precipitates.