Crosslinked Acid-based Fracturing Fluid System

Acid fracturing deeply is one of the key technique for the carbonate reservoir stimulation. During this process, acid liquid system is crucial. It helps to achieve this goal that viscous acid, emulsified acid, foamed acid have been applied. But the technology needs to be developed. The lithological character is especial and complicated, material property is disadvantageous, which is the reservoir characters for the san-tang-hu basin er-die-xi fracturing oil reservoir. Deposited oil floor are composed of muddy limestone and calcic mudstone mainly, but also involving of calcareous sandstone,muddy limestone,calcic mudstone and siltstone alternately, whose permeability is poor or very poor. This zone have been stimulated time after time, but the effect isn't satisfied. therefore the technology innovation will be needed. this paper aims at this purpose to research the crosslinked acid gel fracturing liquid system(for short CLAFLS).According to the basic principle of the crosslinked acid, concerning main agent, because the improved PAM has many merits such as viscosifying performance,acid proof ,stabilization at high temperature> shearing tolerance> salt resisting etc, we chose to synthesize the cationic macromolecular compound as the acid densifier. This paper try to compose the acid viscosifying agent named CH—Ⅱ,which is the copolymer of methacryloyloxyethyltrimethyl ammonium chloride(DMC) and acrylamide(AM); The influential factors of polymerization reaction have been studied (such as catalyst, PHn mass ratio of monomers , total concentration of monomers, the type and mass of initiator, temperature and reaction time etc). IR and H-NMR structural symptom have been carried out for composing outcome. On the basis of the CH—Ⅱ, this paper studied and selected the compatible cross linking agent and multiple breaker. The respective performance experiment shows that: the CH—Ⅱ has the good acid dissolubility and thickness ability, the cross linking agent's crossing performance is excellent. What's more, this paper also has further studied two mainly parameter: crossing-proportion and temperature, which affected the crossing-performance sharply. The liquid is clear and brightsome after the gel has breaked.With regard to single agent, much contrasting , selecting and appraising experiment has been carried out. Cationic polymer clay stabilizer named BD1-13 has been selected, which overmatch KC1 used in oilfield frequently.; The ferric ion stabilizer named KMS-7 has been selected, which overmatch kindred FCFR and BD1-2; The acid corrosion inhibitor named KMS-6 has been selected, which overmatch kindred BA1-11 and HJF-94; The cleanup additive named SD2-9 has been selected, which overmatch kindred BD1-5, KMS-8 ,CF-2. All these single agent is compatible with the main agent. Taking into account the result of the acid...