Gelled emulsions and methods of using the same

Abstract

Gelled emulsions contain (i.) an external phase of an aqueous water-soluble solvent solution, polymeric viscosifying agent and, optionally, an oxidative and / or acidic breaker; and (ii.) an internal phase of a dispersed organic fluid. The aqueous water-soluble solvent solution constitutes between from about 15 to about 50 volume percent of the gelled emulsion and the dispersed organic fluid is presented in the gelled emulsion in amounts ranging from about 50 to about 85 volume percent. The gelled emulsions are useful in a variety of applications including, but not limited to, oil field, pipeline and processing facility applications.

Description

FIELD OF THE INVENTION[0001]The invention relates to gelled emulsions which contain an aqueous water-soluble solvent solution. The gelled emulsions are essentially phosphate-free. The invention further relates to methods of using such gelled emulsions.BACKGROUND OF THE INVENTION[0002]Stimulation techniques, such as hydraulic fracturing, used in the treatment of oil and gas wells improve productivity of the treated well. In hydraulic fracturing, a fluid is injected down the wellbore and into the productive formation at a sufficient rate and pressure such that the formation rock fractures from the induced stresses. A proppant is added to the fluid and is carried into the formation fracture. The proppant prevents closure of the fracture when hydraulic pressures are released, thereby leaving a conductive flow channel from the wellbore deep into the rock matrix.[0003]Traditionally the fluid used for the purpose of hydraulic fracturing has been oil, water, or an emulsion of these two liqu...

AI Technical Summary

Benefits of technology

[0012]Additives and mixing methodology may be employed in order to delay the hydration of the polymeric viscosifying agent. As such, the initial viscosity of the gelled emulsion may be minimized; the viscosity of the emulsion being allowed to increase over time. This, in turn, minimizes pumping friction pressure.

Problems solved by technology

In the case of methanol, it is also very volatile and will therefore evaporate even in the presence of water saturated gases.

Glycol, however, is more costly than methanol and exhibits lower volatility.

The disclosed emulsions are further undesirable since, at elevated temperatures and pressures, hydrocarbons (such as kerosene and diesel fuel) become miscible and a low viscosity, single phase liquid results.

Concerns have arisen, however, regarding residual phosphorous compounds (which may remain in the crude and cause refinery upsets) as well as contamination of refined petroleum products.

While non-phosphate-based hydrocarbon gellants have been developed, such as those disclosed in U.S. Pat. No. 6,849,581, they are often slow to gel at low temperature.

Other non-phosphate-based hydrocarbon gellants are too expensive to be commercially viable.

Further, the gelation rates and stability of many of the non-phosphate-based hydrocarbon gels of the prior art are severely affected by contaminants such as, for example, water.

This further makes them commercially undesirable.

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