Delayed Zirconium Crosslink of GelledAcid Provides Broader Range ofAcid Fracturing Injection Rates

摘要

One of the most effective methods of carbonate stimulationis acid fracturing. Development of fracture geometry sufficientto allow etched penetration to provide an economic productionincrease is dependent upon several factors, one of which ispump rate. High rates and/or lower hydraulic horsepowerrequirements can be critical to success to one of these projects. Many times a wellbore lacks the integrity or flexibility to betreated down casing. Treating down tubing affords highlyviscous fluid's opportunity for rate restrictions due to largefriction pressures observed when pumping acid. In addition, fluids of high viscosity based on the crosslinking of polymersusing zirconium are known to have shear limitations. Therefore, adequate fracture geometry in this type of a well hasbeen unattainable.Laboratory testing and case histories are presentedregarding the evaluation and usage of zirconium crosslinkedhydrochloric acid systems in the acid fracturing of severalcarbonates utilizing a variety of tubulars. Major emphasis is onthe friction pressures observed on wells treated down 7.303 cm(2.875 inch)and 11.43-cm (4.5-inch)O.D. tubulars. Also, laboratory results on the effect of shear on the stability of zirconium crosslinked gelled hydrochloric acid viscosity ispresented. In addition, the crosslink delay effect on ultimateviscosity is presented.