Successful Treatment of a Green River Sandstone Formation Using a Novel Low-Polymer Crosslinked Fluid

Abstract

Abstract Guar-based fracturing fluids are the most commonly used fluids in reservoir stimulation. To provide high viscosity, borate crosslinked gels are preferred for their ability to heal after mechanical shearing and their favorable environmental properties. More efficient crosslinkers capable of cross-linking fluids with reduced polymer loading have always been of great interest to reduce formation and proppant pack damage from polymer residues, and to reduce overall fluid cost. Low permeability and the interwell connectivity of Green River sandstone formations of the Uintah Basin require hydraulic fracturing treatment to economically produce oil. The most typical fracturing treatments use guar crosslinked borate fluids to transport sand into wells with vertical depths of 3500-6,800 feet and bottom-hole temperatures of 115-160°F. Most operators in this area place emphasis on reduced polymer loadings for stimulation treatments; and even with breakers present, broken polymer residues can remain in the formation even at these reduced polymer loadings, resulting in damage and decreased production. The stimulations for these wells are flow backed at the end of the last stage. This poses a challenge of a proper balance between polymer and breaker loading, so that the fluid effectively transports up to 6 pound per gallon added (ppa) of sand into the formation without screen out, and breaks within the treatment time (30-40 minutes per stage) to minimize flow back of proppant. Recently developed novel poly-aminoboronate crosslinker (also reported in SPE 140817 and SPE 164118) was tested in the aforementioned formation. Multiple boron sites are available in the crosslinker and it is capable of interacting with multiple polysaccharide strands to form more complex crosslinking networks at lower polymer loadings than conventional guar fluids. The crosslinker with up to additional 15% reduced guar loading is capable of matching or out performing conventional crosslinked fluids in fresh water and more impressively in 7% KCl. This paper will discuss the novel crosslinker developed, the laboratory testing and successful field application. Analysis and discussion of the chemistry, crosslinking performance and economics will be presented.