Earth boring – well treating – and oil field chemistry – Well treating – Contains inorganic component other than water or clay
Reexamination Certificate
1999-09-29
2001-04-10
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains inorganic component other than water or clay
C507S209000, C507S211000, C507S273000, C507S903000, C507S921000, C507S922000, C166S308400
Reexamination Certificate
active
06214773
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved high temperature, low residue viscous ell treating fluids and methods of using the fluids for treating subterranean zones.
2. Description of the Prior Art
High viscosity aqueous cross-linked gels are used in a variety of operations and treatments carried out in oil and gas wells. Such operations and treatments include, but are not limited to, production stimulation treatments, well completion operations, fluid loss control treatments 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 a carrier fluid for particulate propping agent, e.g., sand. That is, the high viscosity fluid is pumped through the well bore into a subterranean zone to be fractured at a rate and pressure such that fractures are formed and extended in the zone. Propping agent is suspended in the fracturing fluid so that the propping agent is deposited in the fractures. The fracturing fluid is then broken into a thin fluid and returned to the surface. The propping agent functions to prevent the fractures from closing whereby conductive channels are formed through which produced fluids can flow to the well bore.
A variety of cross-linking compounds and compositions have heretofore been utilized for cross-linking gelled aqueous well treating fluids. Various sources of borate have been utilized including boric acid, borax, sodium tetraborate, slightly water soluble borates such as ulexite, and other proprietary borate compositions such as polymeric borate compounds. Various compounds that are capable of releasing multivalent metal cations when dissolved in aqueous well treating fluids have also been used heretofore for cross-linking gelled aqueous well treating fluids. Examples of the multivalent metal ions are chromium, zirconium, antimony, titanium, iron, zinc and aluminum.
Delayed cross-linking compositions have also been utilized heretofore such as compositions containing borate ion producing compounds, chelated multivalent metal cations or mixtures of organotitanate compounds and polyhydroxyl containing compounds such as glycerol. However, high viscosity aqueous gels cross-linked with the above described cross-linking agents and compositions have encountered operational problems. That is, the high viscosity cross-linked gelled aqueous well treating fluids have often been difficult to break after being placed in a subterranean zone and upon breaking, leave residue in the subterranean zone, both of which interfere with the flow of produced fluids from the treated zone. Further, at high subterranean zone temperatures in the range of from about 125° F. to about 350° F., a relatively large quantity of gelling agent is required in the cross-linked gelled aqueous well treating fluid to achieve adequate viscosity which produces a greater amount of residue in the treated zone and the high viscosity produced rapidly declines with time.
Thus, there are needs for improved high temperature well treating fluids and methods of using such fluids wherein the fluids require less gelling agent thereby reducing the residue left in subterranean zones treated therewith and the treating fluids have high viscosities which are stable over time at high temperatures.
SUMMARY OF THE INVENTION
The present invention provides high temperature, low residue well treating fluids and methods which meet the needs described above and overcome the deficiencies of the prior art. The improved viscous well treating fluids of the present invention are basically comprised of water; a hydrated galactomannan gelling agent present in the treating fluid in an amount in the range of from about 0.12% to about 0.48% by weight of the water in the treating fluid; a retarded cross-linking composition for buffering the treating fluid and cross-linking the hydrated galactomannan gelling agent comprised of a liquid solvent, an organotitanate chelate, and a borate ion producing compound, the retarded cross-linking composition being present in the treating fluid in an amount in the range of from about 0.04% to about 1.0% by weight of water in the treating fluid; and a delayed gel breaker for causing the viscous treating fluid to break into a thin fluid present in the treating fluid in an amount in the range of from about 0.01% to about 2.5% by weight of water in the treating fluid.
The improved methods of this invention for treating a subterranean zone penetrated by a well bore are basically comprised of the following steps. A viscous low residue well treating fluid is prepared comprised of water; a hydratable galactomannan gelling agent; a retarded cross-linking composition comprised of a liquid solvent, an organotitanate chelate, a borate ion producing compound; and a delayed gel breaker. The prepared well treating fluid is then pumped into the subterranean zone at a rate and pressure sufficient to treat the zone by way of the well bore during which the hydrated gelling agent in the treating fluid is cross-linked by the retarded cross-linking composition. Thereafter, the viscous treating fluid is allowed to break into a thin fluid.
In fracture stimulation treatments using the viscous low residue well treating fluid, the treating fluid is pumped into the subterranean zone at a rate and pressure such that one or more fractures are formed in the zone and particulate solid propping agent carried by the treating fluid is deposited in the fractures.
It is, therefore, a general object of the present invention to provide improved high temperature, low residue viscous well treating fluids and methods of using such 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
As mentioned above, the improved high temperature, low residue well treating fluids of this invention utilize low gelling agent concentrations in high temperature applications, i.e., 5 to 10 pounds of gelling agent per 1,000 gallons of water less than has been typically utilized in high temperature applications heretofore. The treating fluids have stable high viscosities and are broken in a controlled manner by the delayed gel breaker included in the treating fluids. Because the treating fluids have less gelling agent and are clear, clean aqueous gels, less residue is left in subterranean zones treated therewith.
The improved treating fluids of this invention are suitable for performing a variety of operations in subterranean zones having high temperatures, i.e., temperatures in the range of from about 125° F. to about 350° F. The treating fluids are particularly suitable for carrying out fracture stimulation procedures in subterranean zones having temperatures in the range of from about 200° F. to about 275° F.
An improved high temperature, low residue treating fluid of this invention is basically comprised of water; a hydrated galactomannan gelling agent present in the treating fluid in an amount in the range of from about 0.12% to about 0.48% by weight of the water in the treating fluid; a retarded cross-linking composition for buffering the treating fluid and cross-linking the hydrated galactomannan gelling agent comprised of a liquid solvent, an organotitanate chelate, and a borate ion producing compound, the retarded cross-linking composition being present in the treating fluid in an amount in the range of from about 0.04% to about 1.0% by weight of water in the treating fluid; and a delayed gel breaker for causing the viscous treating fluid to break into a thin fluid present in the treating fluid in an amount in the range of from about 0.01% to about 2.5% by weight of water in the treating fluid.
The water utilized to form the improved treating fluids of this invention can be fresh water, salt water, brine
Barrick David M.
Harris Phillip C.
Heath Stanley J.
Milson Shane L.
Powell Ron J.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Tucker Philip
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