Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
1998-11-23
2001-02-06
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S269000, C507S921000, C507S902000
Reexamination Certificate
active
06184184
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and compositions for fracturing subterranean formations. In particular, the present invention describes a novel encapsulated breaker for use with a fracturing fluid such as those described in co-pending Canadian patent application No. 2,237,383.
BACKGROUND OF THE INVENTION
In order to increase the productivity of oil and gas wells, or to bring back into production wells that have essentially gone dry, it is common practice to conduct a procedure known as fracturing the well. In such a procedure, fluids known as fracturing fluids, are injected into the well at very high hydrostatic pressures. The fluids are typically viscous gels, and act under pressure to open pores and cracks in the formation, thereby to increase the overall permeability of the well. Typically, the fluids also are used to transport proppants, such as sand or ground walnut shells into the cracks and pores, thereby to ensure that the pores and cracks formed during fracturing remain open under the lower pressures that will exist after fracturing, when the well is producing.
The fluid that has been used to fracture the formation is removed by the introduction of viscosity lowering agents into same, which permit the fluid to be more easily pumped from the formation. These agents are known as breakers because they tend to break down the fracturing gel. Breakers can act on a gel in a number of ways, such as by the random oxidation of polymers to shorten the chain length thereof. In the present invention, a breaker is utilized to adjust the pH of a gel, to break same by hydrolysis.
The fracturing fluid of the present invention is a phosphate alkyl ester gel. It is known that a gel can be produced by mixing trivalent cations, such as aluminum, with a phosphate alkyl ester. However, gels obtained with known phosphate alkyl esters have not been commercially acceptable, because the viscosity developed with same has been insufficient or slow to develop, and usually required tank mixing.
Phosphate alkyl esters may be mono-esters, di-esters or trimesters. In the mono-ester, one primary mono-hydric alcohol, of C
5
-C
16
length is ester linked to a phosphate. A di-ester has two such alkyl alcohols linked to a phosphate. A tri-ester has three alkyl alcohols linked to it. The applicants have discovered that commercially valuable gels are feasible with a di-ester content above 50%, preferably above 65%, and a tri-ester content below 5%. The remainder may be mono-ester.
The applicants enhance gel development in two important ways. First, the phosphal alkyl esters are neutralized with primary amines. Secondly, the applicants utilize a surfactant to enhance gel development. An appropriate surfactant is ammonium alkyl (C
6
-C
20
) sulfate.
In order to break the gel described herein the preferred breaker of the present invention is a pH adjusting breaker, such as calcium oxide and sodium carbonate. It is preferred that the breaker be encapsulated in a porous inert substance, such as nylon.
In a broad aspect, then, the present invention relates to an encapsulated breaker for a fracturing fluid for use in fracturing subterranean formations comprising: a hydrocarbon base; and neutralized alkyl phosphate esters complexed with metallic cations, to form a gel, in said hydrocarbon base.
REFERENCES:
patent: 4506734 (1985-03-01), Nolte
patent: 4741401 (1988-05-01), Walles et al.
patent: 4787994 (1988-11-01), Thorne et al.
patent: 4919209 (1990-04-01), King
patent: 5164099 (1992-11-01), Gupta et al.
patent: 5624886 (1997-04-01), Dawson et al.
patent: 5649596 (1997-07-01), Jones et al.
patent: 5948735 (1999-09-01), Newlove et al.
patent: 2237383 (1998-05-01), None
Amin Junad
Gupta Satyanarayana
Fracmaster Ltd.
Lerner David Littenberg Krumholz & Mentlik LLP
Tucker Philip
LandOfFree
Encapsulated breaker for oil gel system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Encapsulated breaker for oil gel system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Encapsulated breaker for oil gel system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571109