Experimental Study On Modification Of High Temperature Resistant Cross-linked Acid System And Gel Breaking Performance

As one of the key technologies for increasing production and stabilizing production of carbonate reservoirs,acid fracturing technology has developed a variety of acid systems suitable for different reservoir conditions.The cross-linked acid system is a highly viscous acid fluid system,which is generally used in the acid fracturing of high-temperature,deep carbonate reservoirs.This liquid system has the characteristics of high viscosity,strong salt resistance,strong sand carrying capacity and long effective distance.However,the existing cross-linked acid system also has the problems of insufficient high temperature resistance and unstable shear resistance,which affects the effect of the cross-linked acid on deep reservoirs.In addition,the defects such as incomplete gel breaking and high residue rate of the conventional cross-linked acid system will not only cause secondary damage to the formation,but also reduce the fracture conductivity and limit the large-scale application of cross-linked acid.Therefore,while improving the temperature and shear resistance of the cross-linked acid,it is necessary to optimize the breaker and improve its breaker performance.In order to improve the temperature resistance and shear resistance of the cross-linked acid,the paper synthesized an organic zirconium cross-linking agent GDJL-1suitable for high-temperature conditions by analyzing the effect of different reaction conditions on the cross-linking performance.,And determine the synthesis of raw materials,reaction temperature and reaction time.The type and amount of crosslinking agent and other additives are optimized.The improved new formula test found that the modified cross-linked acid system's rheological properties,sand carrying performance and fluid loss performance are better than the general cross-linked acid system.The higher residue of conventional cross-linked acid is the important work of the thesis.When optimizing the breakers,it was found that ammonium persulfate?APS?breakers were quickly consumed when exposed to cross-linking acid under high temperature conditions,and it was impossible to effectively and thoroughly break the preferred high-temperature cross-linking acid formula to slow down the breaker.The release rate of the active ingredients of the agent should be an important entry point to improve the gel breaking effect.Starting from this mechanism in the experiment,the capsule-type APS and the activator to promote the decomposition of the active ingredients of the APS capsule were studied separately.The experiment found that when the concentration ratio of sodium sulfite?Na₂SO₃?,inorganic salt RA,and APS capsule was 0.4:1.6:2.0,the gel was broken The time is greatly shortened and the amount of residue is low.In order to further improve the gel-breaking performance of the cross-linked acid system,the experiment also added a chelating agent to the gel breaker.The principle is to use chelation to chelate with the metal ion of the cross-linking agent to passivate it and destroy the cross-linking to a certain extent.Spatial structure of cross-linked acid reduces viscosity of cross-linked acid.Through the combined use of chelating agents,the gel breaking time is significantly shortened and the gel breaking effect is significantly improved.The modified cross-linked acid system has improved temperature and shear resistance.At the same time,it is compounded with a new type of breaker to shorten the breaking time and reduce the residue of the breaker liquid,so that the cross-linked acid is at high temperature The reservoir fracturing construction application has better adaptability and application effect.