Compositions – Leather or fur treating
Patent
1992-06-12
1994-09-27
Geist, Gary
Compositions
Leather or fur treating
166283, 166308, E21B 4326
Patent
active
053505280
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to methods for fracturing geological formations in the region of hydrocarbon bearing zones in order to stimulate production of desired hydrocarbon fluids. The present invention also relates to hydraulic fracturing fluids which demonstrate improved rheological properties for delivering a proppant into fractures in order to maintain them in a highly permeable condition for improved hydrocarbon recovery. The invention further relates to methods for preparation and use of such a fluid.
BACKGROUND OF INVENTION
Hydraulic fracturing of oil bearing formations has been practiced commercially for many years. Conventional hydraulic fracturing techniques involve pumping a fluid at a sufficiently high pressure and volumetric rate through a well hole lined with a steel pipe and into a hydrocarbon bearing zone to cause cracks to form and propagate within the surrounding geological formation. Although both oil-based and water-based fracturing fluids are available, water-based fracturing fluids are generally more economical, and they offer greater control over a broader range of physical properties than oil-based fluids. Water-based fracturing fluids are now generally preferred by the hydrocarbon retrieval industry. The following discussion and the present invention is directed to water-based fracturing fluids.
Fracturing fluids generally contain several components. Among the most important components are a proppant, which is a granular solid material, and a gellant, which controls rheological properties of the fracturing fluid. Proppants are typically chosen from highly rounded natural silica sand and from ceramic materials such as alumina. Alumina is preferred whenever compressive forces are expected to be high. Numerous other additives found in fracturing fluids include pH buffers, surfactants, clay stabilizers, biocides, and fluid-loss additives. Many of these specific chemicals used in the fracturing process are described in Chemicals in Petroleum Exploration and Production II, North American Report and Forecasts to 1993, Colin A, Houston and Associates, Inc., Mamaroneck, N.Y. (1984).
A primary purpose of fracturing fluids is to distribute the proppant in cracks formed and propagated during fracturing, causing them to remain open after the pressure is released. Uniform distribution of proppant in cracks tends to greatly increase the permeability of a geological formation, especially of a very tight formation, and enable a greater recovery and higher flow rate of hydrocarbons contained within the formation.
Hydraulic fracturing has become a relatively predictable practice. The orientation and lengths of cracks can, under certain circumstances, be substantially predetermined and controlled. The Petroleum Engineering Handbook, H. B. Bradley, ed., Society of Petroleum Engineers, Richardson, Tex., Chap. 55 (1987) presents a useful background discussion of hydraulic fracturing.
While the term "gellant" is in common use in the hydrocarbon recovery industry in connection with fracturing fluids, the term should not be taken literally to mean that fracturing fluid gellants form conventional nonflowing gels. Fracturing fluid gellants may be more appropriately classified as viscosifiers and rheology control agents. A primary purpose of the gellant is to maintain the proppant in suspension during fluid preparation, pumping, and distribution into the well hole and cracks generated within a hydrocarbon bearing formation. Gellants therefore should function under diverse shear conditions. For example, several hundred thousand liters of fracturing fluid may be injected into a well at pumping rates as high as 7950 L/min. Ideally, the viscosity of the fluid should be low during fluid mixing and pumping to minimize the energy required during these operations. The viscosity should be high enough, however, so that the proppant does not fall out of suspension and is delivered to its desired location. High temperatures in hydrocarbon bearing zones further complicate the rheological properties
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Penny Glenn S.
Stephens R. Scott
Westland John A.
Winslow Alan R.
Geist Gary
Weyerhaeuser Company
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