Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
1999-10-12
2001-10-30
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S268000, C507S209000, C507S211000, C507S271000, C507S273000, C507S903000, C507S922000, C166S308400
Reexamination Certificate
active
06310008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improved cross-linked aqueous well treating fluids and methods for preparing and using such fluids for treating subterranean zones in wells.
2. Description of the Prior Art
High viscosity aqueous cross-linked gels are used in a variety of operations and treatments in oil and gas wells. Such operations and treatments include, but are not limited to, well completion operations, fluid loss control treatments, production stimulation treatments, formation permeability conformance operations, and treatments to reduce water production.
An example of a production stimulation treatment utilizing a high viscosity cross-linked gelled fluid is hydraulic fracturing. In hydraulic fracturing treatments, the high viscosity fluid is utilized as a fracturing fluid and also carries particulate propping agents, e.g., sand, into the fractures formed. That is, the fracturing fluid is pumped through the wellbore into a formation to be stimulated at a rate and pressure such that fractures are formed and extended in the formation. The propping agent is suspended in the fracturing fluid so that it is deposited in the fractures when the gel is broken and returned to the surface. The propping agent functions to prevent the formed fractures from closing whereby conductive channels are formed through which produced fluids can flow to the wellbore.
An example of a well completion operation involving the use of a high viscosity aqueous cross-linked gel is gravel packing. In gravel packing operations, solid gravel particles such as sand are carried to the subterranean zone or formation in which a gravel pack is to be placed by a high viscosity cross-linked gelled fluid. That is, the gravel is suspended in the high viscosity fluid at the surface and carried to the subterranean zone or formation in which the gravel pack is to be placed. Once the gravel is placed in the zone or formation, the cross-linked gel is broken (degraded) and returned to the surface. The gravel pack produced functions as a filter to separate formation solids from produced fluids while permitting the produced fluids to flow into and up the wellbore.
Borate ion has long been used as a cross-linking agent for forming high viscosity cross-linked gelled aqueous well treating fluids. Various sources of borate ion have been utilized including boric acid, borax, sodium tetraborate, slightly water soluble borates such as ulexite, and other proprietary compositions comprising boric acid and dimers and trimers of borate ions. Numerous sources of borate cross-linking solutions are known in the art. U.S. Pat. No. 5,310,489 issued to Sharif on May 10, 1994; U.S. Pat. No. 5,266,224 issued to Sharif on Nov. 30, 1993; U.S. Pat. No. 5,252,236 issued to Sharif on Oct. 12, 1993; and U.S. Pat. No. 5,160,445 issued to Sharif on Nov. 3, 1992, which are incorporated herein by reference, disclose borate cross-linking solutions that may be useful in the present invention.
Polyvalent metal cations have also been used as cross-linking agents to form gelled aqueous well treating fluids. U.S. Pat. No. 5,145,590 issued to Dawson on Sep. 8, 1992, discloses that polyvalent metal cations including aluminum, antimony, zirconium and titanium containing compounds have been used to cross-link polymers used as well treating fluids. U.S. Pat. No. 4,514,309 issued to Wadhwa on Apr. 30, 1985, discloses a cross-linking system based on titanium and boron, including organotitanate compounds.
For well treating fluids to function properly, the fluids must remain viscous until the desired well operation or treatment has been completed. For example, the well treating fluids must remain viscous in a fracture long enough to permit build-up and maintenance of sufficient pressure to open a fracture and the fluid must retain its viscosity as it flows into the fracture to support the propping agents suspended in the fluid. Similarly, the well treating fluids must remain viscous in a gravel packing operation until the gravel is in place. Often, however, prolonged exposure of a well treating fluid to the temperatures encountered in the well causes the fluid to prematurely degrade and lose its viscosity. Many such fluids lose significant viscosity in a few hours at the temperatures experienced downhole, some in the range of from about 150° F. to 400° F., but usually in the range of from about 200° F. to 300° F. Preferably, a well treating fluid should retain its viscosity for up to 8 hours at temperatures of about 200° F. to 300° F.
There is, therefore, a need for improved cross-linked well treating fluids that can retain their viscosity for prolonged periods of time and methods for preparing and using such fluids for treating subterranean zones in wells.
SUMMARY OF THE INVENTION
The present invention provides improved cross-linked gelled aqueous well treating fluids comprising water, a galactomannan gelling agent, a cross-linking agent for cross-linking the galactomannan gelling agent, and a viscosity stabilizing agent selected from the group consisting of formaldehyde, formic acid, or mixtures thereof.
Generally, the galactomannan gelling agents and the cross-linking agents used in the present invention are those known in the art. Typical galactomannan gelling agents include naturally occurring gums and their derivatives and typical cross-linking agents include water soluble borate ion releasing compounds, polyvalent metal cation releasing compounds capable of releasing cations such as magnesium, aluminum, titanium, zirconium, chromium, and antimony, and compositions containing these compounds. A cross-linking composition useful in accordance with the present invention comprises water in an amount of from about 96% to about 5% by weight of the composition and a water soluble cross-linking agent in an amount of from about 4% to about 95% by weight of the composition. The cross-linking composition may also contain an alkanolamine or alkylamine buffer present in an amount of from about 1% to about 13% by weight of the composition. The alkanolamine is preferably an ethanolamine, most preferably monoethanolamine.
The galactomannan gelling agent is present in the treating fluid in an amount of from about 0.06% to about 0.72% by weight of water, the cross-linking agent is present in the treating fluid in an amount of from about 0.01% to about 1% by weight of water, and the viscosity stabilizing agent is present in the treating fluid in an amount of from about 0.001% to about 1% by weight of water.
The methods for using the improved cross-linked well treating fluids of the present invention comprise the steps of preparing a treating fluid of the invention and then introducing the treating fluid into a subterranean zone or formation penetrated by a wellbore.
The methods for preparing the improved cross-linked well treating fluids of the present invention comprise the steps of dissolving a galactomannan gelling agent in water to form a gelled aqueous fluid and then combining a cross-linking agent and a viscosity stabilizing agent of the invention, i.e., formaldehide, formic acid, or a mixture thereof, with the gelled aqueous fluid.
It is, therefore, an object of the present invention to provide improved cross-linked aqueous well treating fluids that retain their viscosity for prolonged periods of time.
Another object of the present invention is to provide improved methods for treating subterranean zones penetrated by a wellbore.
A further object of the present invention is to provide improved methods for preparing cross-linked aqueous well treating fluids.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides improved cross-linked aqueous well treating fluids comprising water, a galactomannan gelling agent, a cross-linking agent for cross-linking the galactomannan gelling agent, and a viscosit
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Tucker Philip
LandOfFree
Cross-linked well treating fluids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cross-linked well treating fluids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cross-linked well treating fluids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2557753