Improved recovery of oil and gas is possible with the use of highly viscous fluids in the hydraulic fracturing process. These are water or oil base gels that help create wider fractures than is possible with the so-called conventional fluids. This allows the placement of additional quantities (concentrations up to six pounds per gallon or more) of highly permeable propping agents in the fracture.

Guar gum, cellulose derivatives and synthetic polymers may be chemically modified to produce the thick gels that have viscosities in produce the thick gels that have viscosities in the 1000 to 20,000 centipoise range. Chemical breakers are added to assure adequate viscosity reduction after the treatment.

The oil-base gel is the latest development representing the introduction of new ester systems that can crosslink in refined oils such as kerosene, diesel oil, and low boiling aliphatic hydrocarbons.

Field results with these viscous gels are summarized. Specific case histories are examine to show improvement over other methods of stimulation.


Since the advent of hydraulic fracturing as a well stimulation tool, a variety of fluids and treatment methods have been proposed and used to improve well productivity. Fluids used in this process over the years include: water, lease oil, process over the years include: water, lease oil, refined oil, water-oil emulsions, acid-oil emulsions, gelled oil, gelled water, and gelled acid. A recent development has been the introduction of thick fluids for hydraulic fracturing. These can carry higher concentrations of propping Agent, and they also produce wider fractures allowing for increased fracture conductivity. Low friction pressures while pumping, even though the fluids appear extremely viscous, allow the treatments to be performed at reasonable injection rates. This paper describes four of these fluid their characteristics, and treatment results that demonstrate the effectiveness of this approach to hydraulic fracturing. These fluids are:

(1) crosslinked guar gel;

(2) crosslinked cellulose;

(3) high concentration synthetic polymer; and

(4) an oil base gel.

Heavy refined oil-water dispersions were recently described by Kiel.

While the volume of fluid employed in hydraulic fracturing treatments has increased markedly, the flow capacity of the fracture has remained relatively constant. In many cases, the formation can feed the fracture faster than the fracture can transmit fluid.

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