Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
2000-04-20
2003-01-14
Lovering, Richard D. (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C166S270000, C166S308400, C252S077000, C507S130000, C507S132000, C507S245000, C507S922000, C507S925000, C510S433000, C510S504000, C516S102000, C524S921000, C554S055000, C564S204000, C564S215000
Reexamination Certificate
active
06506710
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gelling agent compositions, to viscoelastic compositions containing them and to methods and agents for modifying the rheological behavior of aqueous fluids such as used in well drilling and similar subterranean operations.
2. Background of the Art
Fluids are used in well drilling operations, for example, to cool and lubricate the drilling bit, to carry away drilled solids and other debris, to suspend drilled cuttings and other debris when the fluid column is static, to control subsurface pressure, to prevent squeezing or caving of formations, to suspend propping agents, and to minimize damage to any potential production zone. In stimulation (hydraulic) operations fluids are used to transfer pressure from one location to another.
Drilling fluids and stimulation fluids can be water based or oil based. Typically, water based drilling and stimulation fluids can include one or more aqueous fluid thickening agents, lubricants, and corrosion inhibitors. The aqueous fluid can be fresh water or brine, and can include aqueous solutions of acids, alkali, lower alkanols (methanol, ethanol, and propanol), glycols, and the like, provided that the water miscible liquid does not adversely affect the viscoelastic properties of the aqueous fluid. Also included are emulsions of immiscible liquids in water and aqueous slurries of solid particulates such as clay.
Viscoelasticity is a desirable rheological feature in drilling fluids, workover or completion fluids, and stimulation fluids which can be provided by fluid modifying agents such as polymeric agents and surfactant gelling agents. Viscoelastic fluids are those in which the application of stress gives rise to a strain that approaches its equilibrium value relatively slowly. Therefore, viscoelastic fluids may behave as a viscous fluid or an elastic solid, depending upon the stress on the system. Viscoelasticity in fluids that is caused by surfactants can manifest itself in shear rate thinning behavior. For example, when such a fluid is passed through a pump or is in the vicinity of a rotating drill bit, the fluid exhibits low viscosity. When the shearing force is abated the fluid returns to its more viscous condition. This is because the viscoelastic behavior is caused by surfactant aggregations in the fluid. These aggregations will adjust to the conditions of the fluid, and will form different aggregation shapes under different shear stress. Thus one can have a fluid that behaves as a viscous fluid under low shear, and a low viscosity fluid under a higher shear. A viscoelastic fluid also has an elastic component which manifests itself in yield value. This allows a viscoelastic fluid to suspend an insoluble material, for example sand, for a greater time period than a viscous fluid of the same apparent viscosity.
Another function of fluid modifying agents in oil drilling applications is in permeability modification. Secondary recovery of oil from reservoirs involves supplementing by artificial means the natural energy inherent in the reservoir to recover the oil. For example when the oil is stored in porous rock it is often recovered by driving a pressurized fluid, such as brine, through one or more drill holes (injecting wells) into the reservoir formation to force the oil to a well bore from which it can be recovered. However, rock often has areas of high and low permeability. The brine injected can finger its way through the high permeability areas leaving unrecovered oil in the low permeability areas.
Various methods have been employed to solve this problem. For example, U.S. Pat. No. 5,101,903 discloses a method for reducing the permeability of the more permeable zone of an underground formation having non-uniform permeability. The method comprises injecting into the formation a blend of surfactant and an alcohol, the blend being introduced in an amount effective to reduce the permeability of the more permeable zone of the formation. The preferred surfactant is an amine oxide such as dimethyltallowamine oxide delivered in water. A disclosed alcohol is isopropanol. The method may include the further step of injecting an alcohol slug following injection of the surfactant and alcohol blend.
U.S. Pat. No. 4,745,976 discloses a method for partially or completely blocking the high permeability regions of a reservoir. The technique is based upon the ability to induce phase changes in surfactant solutions by changing counterions or by adding small quantities of different surfactants. An aqueous solution of an ionic surfactant may have a viscosity only slightly different from brine but an increase in the salt concentration or addition of a multivalent counterion can cause the surfactant to form a solid precipitate or form a gel-like structure of high viscosity. In the method of U.S. Pat. No. 4,745,976, a first surfactant solution is injected into the formation followed by a water-soluble spacer fluid followed by a second surfactant solution. In situ mixing of the two surfactant solutions is affected by the tendency of different surfactant types to travel at different velocities through the reservoir. The compositions of the first and second surfactants solutions are chosen so that upon mixing, a precipitated or gel-like structure will form blocking the high permeability zone of the reservoir.
SUMMARY OF THE INVENTION
In accordance with the present invention, the rheology of an aqueous fluid is modified by the method which comprises adding to an aqueous fluid an amount of gelling agent sufficient to form a viscoelastic fluid, the gelling agent and/or viscoelastic surfactant being an amidoamine oxide of the general formula I:
wherein R
1
is a saturated or unsaturated, straight or branched chain aliphatic group of from about 7 to about 30 carbon atoms, R
2
is a divalent alkylene group of 2-6 carbon atoms which may be linear or branched, substituted or unsubstituted, and R
3
and R
4
are independently C
1
-C
4
alkyl or hydroxyalkyl groups or together they form a heterocyclic ring of up to six members, and R
5
is hydrogen or a C
1
-C
4
alkyl or hydroxyalkyl group.
The aforementioned gelling agents advantageously provide clear gels that do not undergo phase separation over extended periods of time and exhibit high heat stability.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention generally relates to a gelling agent composition, to an aqueous viscoelastic composition comprising said gelling agent, to a method for manufacturing said gelling agent composition, to a method of stimulating and/or modifying the permeability of an underground formation with the gelling agent and/or aqueous viscoelastic compositions of the present invention, and to drilling fluids, completion fluids, workover fluids and the like comprising the gelling agent composition of the present invention. The gelling agent compositions of the present invention can also be employed to gel most other aqueous systems, such as those utilized in cleaning formulations, water-based coatings, detergent formulations, personal care formulations, water based asphalt formulations and the like.
An aqueous viscoelastic composition especially useful in underground applications can be obtained by adding one or more gelling agents such as described below. The concentration of gelling agent in the aqueous composition is generally in the range of from about 0.5% to about 10% by weight, preferably from about 2% to about 8% by weight, and more preferably from about 4% to about 6% by weight based on the total weight of the composition. The aqueous composition of the invention can include inorganic salts and various additives as described hereinbelow. Such a composition is advantageously injected into, for example, an underground system for use in drilling, stimulation (such as hydraulic fracturing), for permeability modification of underground formations, and for uses such as gravel packing, and cementing.
The gelling agents disclosed and described herein are surfactants that can be added singly or they c
Dery Maurice
Dobson Randy E.
Engel Michael
Franklin Ralph
Gadberry James F.
Akzo Nobel N.V.
Lovering Richard D.
Mancini Ralph J.
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