Use of Guar Gum and Synthetic Cellulose in Oilfield Stimulation Fluids

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The use of polysaccharides to alter the rheological properties of aqueous fracturing fluids has been a common practice for many years. In certain cases the inherent properties of these natural and synthetic polymers have been negated by their sensitivity to adverse parameters present in both the base fluid and the formation. Some of these parameters have been identified as ionic strengths, transition metal concentrations, high bottom hole temperatures, and chemical redox systems. Chemical solutions to these problems, which eliminate or minimize the detrimental effects, have been developed for field operations. Once the problem has been recognized and defined, an appropriate chemical treatment will usually make the field water usable, bypassing the necessity of finding an alternate supply. The specific treatment will depend on whether the end product is to be the polymer sol or a complex gel. Additional beneficial effects have been observed as a result of at least two of these chemical treatments. Higher base viscosities of the polymer sol and less polymer sensitivity to the ionic strength of the field polymer sensitivity to the ionic strength of the field waters have been noted in several instances. Exceptional polymer stability at higher temperatures has been obtained polymer stability at higher temperatures has been obtained with one procedure. This has effectively extended the usefulness of several polysaccharides at higher bottom hole temperatures. This paper presents a description of the various polysaccharide systems, their sensitivities, and the methods employed in countering these sensitivities. Introduction Since its inception, the art of hydraulic fracturing has employed an extensive array of fluids and systems. Polymers were initially developed to reduce pumping Polymers were initially developed to reduce pumping friction losses. Almost simultaneously, polymers were found useful in improving propping agent transportability and placement. The efficiency of frac fluids was later improved by additives which controlled fluid leak-off in more permeable reservoirs and in this role polymers were found to play an important part. More recently, the search for further improvement in fluid loss control, proppant transport and placement, and fracture extension proppant transport and placement, and fracture extension brought about the use of crosslinking agents to form super-viscous gels where three-dimensional networks are produced in the polymer solution. produced in the polymer solution. Howard and Fast reported properties which a frac fluid should possess.