Evaluation of Inorganic-Crosslinked-Based Gelled Acid System forHigh-Temperature Applications

摘要

Hydrochloric(HCl)crosslinked gelled acid systems have been extensively used in acid fracturing and matrixacidizing to help achieve acid diversion during stimulation treatments.These systems also help controlfluids leakoff and help retard the acid reaction to allow deeper acid penetration.Currently,many in-situcrosslinked gelled acid systems generally consist of polymers,an iron crosslinker,and a breaker agent,inaddition to other additives.This paper discusses an alternative crosslinker that provides effective diversionwith minimal residuals at temperatures up to 275°F.A non-iron-based crosslinker has been developed for in-situ high-strength gelled acid systems that varybetween 5 to 20 wt% HCl acid.The coreflooding experiments were effectively conducted for permeabilityranges of up to 70 md.This system showed a stable fluid at downhole conditions,initially building viscositybetween a pH range of 1.5 to 3.0.Then,as acid continues to further react with calcium carbonate and the pHbecomes higher than 3,the crosslinked fluid begins to break down and the fluid viscosity decreases.Severalexperiments were conducted to assess the performance of this novel system.Additionally,corrosion testswere performed to evaluate the treatment fluid corrosion rate at a temperature of 275°F.The testing results show that the evaluated gelled acid system is stable at temperatures up to 275°F.The system profile as a function of pH showed the ability to provide diversion during different stimulationtreatments.Additionally,the coreflood results showed that the new gelled acid is capable of formingwormholes without any significant associated formation damage caused by the gel.The effect of corrosioninhibitors on this system at 300°F,along with other additives,was also investigated.