Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
1997-03-05
2001-03-06
Neuder, William (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C166S295000
Reexamination Certificate
active
06196315
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods for treating subterranean earth formations. More particularly, the invention relates to improved methods for treating wells to form an impermeable plug where needed. Such impermeable plugs can be used to reduce the permeability of a water producing interval, to reduce the flow of water into a well producing oil from other intervals, or for closing holes or leaks in well casing, or for closing flow chambers in cement, or voids behind the casing.
BACKGROUND OF THE INVENTION
U.S. Pat. Nos. 5,005,647 and 5,005,648 assigned to the present assignee teach the treatment of subterranean earth formations in cased well boreholes by injecting under hydraulic or gravity pressure a treating fluid comprising a polymerizable material which can be acid catalyzed to cure or set in a period of from 1 to 16 hours at formation conditions. The single step injection is performed with the treating fluid which (for high temperature use) contains an oligomer or monomer of furfuryl alcohol, an ester such as ethyl or butyl acetate and a catalyst such as orthonitrobenzoic acid or toluene sulfonic acid in a concentration of from 1% to 4% by weight which is selected to produce a set time at formation temperature in the range of 1 to 16 hours. These are taught in detail in the above referenced two U.S. patents which are incorporated herein by reference for all purposes.
A great number of successful well treatments have been made according to the teachings of the referenced patents. However, a persistent problem which has arisen in some wellbore environments in the placement of such liquid resins for treating formations for water, gas or sand shutoff, has been the excessive leakoff of treating fluid encountered within an interval that has a high permeability zone or a large void space such as exists in a “washed out” region near the borehole. In this environment a large volume of relatively expensive resin can leak off into the unexpected high permeability zone or void prior to the resin setting. This can require repeat treatments to completely cure the problem of water, gas or sand shutoff.
Accordingly, in spite of the successes of the referenced prior patented methods, there is still a substantial unfulfilled need for an inexpensive, simple and reliable procedure which can be applied to wellbore formations in which a high permeability zone or washed out or void region exists near the borehole for shutting off water from a water producing interval, gas from gas producing intervals, for plugging leaks in well casing or flow channels in cement around the casing using a polymerizable composition, and for reducing the cost of such treatment.
BRIEF SUMMARY OF THE INVENTION
In the methods of the present invention a two step technique is disclosed for placing a polymerizable resin treating fluid in a desired borehole interval. In the techniques of the present invention the treating fluid resin, comprising (for use to above 200° F.) a monomer or oligomer of furfuryl alcohol, an ester such as ethyl acetate or butyl acetate, and possibly a water swelling polymer such as copolymer of starch and synthetic polymer such as acrylates or acrylamides, is hydraulically or gravity injected into the desired interval. In a second step, either prior to the injection of the treating fluid resin, or subsequent to the injection of the treating fluid resin, as desired, a sufficient quantity of acid catalyst, such as orthonitrobenzoic acid, toluene sulfonic acid or any other acid is injected to “flash set” the treatment fluid resin. The “flash setting” process raises the internal heat of the setting reaction and causes the solvents used in the resin formulation to boil. This creates gas bubbles throughout the consolidated resin. This, in turn, causes the consolidated resin to become a foam and to occupy a volume of from two to three times its normal space. Because of the random distribution of the bubbles and their lack of connectivity the consolidated resin material remains impermeable, forming a good permeability barrier. This occurs to some extent even with the resin under borehole encountered pressures. Thus, washouts or unexpected voids are filled without the undue use of excess resin. This significantly reduces costs and the necessity for repeat treatments to obtain shutoff.
REFERENCES:
patent: 3727691 (1973-04-01), Muecke et al.
patent: 3844351 (1974-10-01), Sutton et al.
patent: 4015995 (1977-04-01), Hess
patent: 4662448 (1987-05-01), Ashford et al.
patent: 5005648 (1991-04-01), Friedman et al.
patent: 5503671 (1996-04-01), Casabonne et al.
patent: 5692566 (1997-12-01), Surles
McKinzie Howard Lee
Surles Billy Wayne
Beard William J.
Delhommer Harold J.
Neuder William
Texaco Inc.
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