METHODS, SYSTEMS, AND COMPOSITIONS FOR THE CONTROLLED CROSSLINKING OF WELL SERVICING FLUIDS

摘要

Disclosed is a composition for reducing the crosslinking time of aqueous polysaccharide solutions, the composition comprising: a) a polysaccharide blended with an aqueous base fluid; b) a borate crosslinking agent having a solubility in water at 22 degrees C (71.6 deg F) ranging from about 0.01 kg/m3 to about 10 kg/m3; and c) a reducing amount of a composition that accelerates the rate at which the borate crosslinking agent promotes the gelation of the polysaccharide, which comprises: (i) a first part selected from the group consisting of KCO2H (potassium formate) and KC2H3O2 (potassium acetate), in an amount of about 90 vol. percent up to about 98 vol. per cent based on the composition c); and (ii) a second part selected from the group consisting of CH3CO2H (acetate), HCO2H (formic acid), NaCO2H (sodium formate), NaC2H3O2 (sodium acetate), KCl (potassium chloride) and KOH (potassium hydroxide) in an amount of about 2 vol. per cent up to about 10 vol. percent based on the composition c). Also disclosed is a method of treating a subterranean formation, the method comprising: a) generating a treating fluid comprising a blend of an aqueous base fluid and a polysaccharide that is at least partially soluble in the aqueous base fluid; b) hydrating the treating fluid; c) generating a borate crosslinking composition comprising a borate crosslinking agent having a solubility in water at 22 degrees C (71.6 deg F) ranging from about 0.01 kg/m3 to about 10 kg/m3; d) generating a composition that controls the rate at which the borate crosslinking composition promotes the gelation of the polysaccharide, said composition comprising: (i) a first part selected from the group consisting of KCO2H (potassium formate) and KC2H3O2 (potassium acetate), in an amount of about 90 vol. percent up to about 98 vol. per cent based on the composition d); and (ii) a second part selected from the group consisting of CH3CO2H (acetate), HCO2H (formic acid), NaCO2H (sodium formate), NaC2H3O2 (sodium acetate), KCl (potassium chloride) and KOH (potassium hydroxide) in an amount of about 2 vol. per cent up to about 10 vol. percent based on the composition d). e) admixing compositions c) and d); adding the admixed composition e) to the hydrated treating fluid b) so as to increase or decrease the crosslinking of the treating fluid for a desired period of time measured in minutes; and g) delivering the treating fluid into a subterranean formation. The polysaccharide can be for example guar, cellulose, starch, galactomannan gum, xanthan, succinoglycan or scleroglucan