Research And Application On The System Of Acid-Base Viscoelastic Fluid

With the continuous development of technique in oil exploration and development, acid fracturing becomes an important technique of reservoir stimulation. It should be studied on the technological measures targetedly to meliorate stimulation effect for ultra-low permeability and difficult-to-produce reservoirs. To improve the development benefit of this low permeable reservoir, this paper ameliorates acid-base viscoelastic fluid system on the basis of former experience; it uses viscoelastic surfactant as thickener and is created when thickener is cross-linked in the acid. It inherits advantages of viscoelastic surfactant fracturing fluid such as low-viscosity, high-elasticity, low-friction, sand-carrying ability and so on. Through the mechanism research, we find that this kind acid fluid can achieve self- diversion acid fracturing according to the progress of acid rock reaction and stimulate low permeable reservoir deeply. Acid-base viscoelastic fluid system combines acidizing and fracturing well,it would get better effect if we use it to acid fracturing with sand carrying.Its several properties show well in the study and it is suitable for the stimulation of low permeable reservoir. Then it is used in the redevelopment of three wells in HuaBei Oil Field ultimately with obvious effect, the success of the performance provides effective technological method for this kind reservoir. By this paper, the main content and recognition can be concluded as followings:(1) This paper has tested the actions of kinetics of reaction between the new acid and limestone, and acquired the related dynamic parameters and equations. Besides, it described acid-etched surface morphology with 3-d laser scanner. All the studies show that the acid presents good retardative property.(2) This paper has studied viscosity behavior of the acid, the result is slightly different from that previously published. Its viscosity raises earlier than the traditional variable-viscosity acid, this is beneficial to prohibit acid from consuming and leaking off.(3) Other properties have been studied exhaustively; the results show that it is low filtration, low friction, shearing resistance, high temperature resistant, high flow conductivity, compatible with other acid. Besides, the reacted acid breaks rapidly and completely, less pollution for the reservoir.(4) This paper designed construction scheme on the one hand, on the other hand, it carried the systematic analysis and evaluations on the effects of acid fracturing, which both aimed at the low permeability lime-sand rock reservoirs of HuaBei Oil Field.Therefore, the new technique mentioned in this paper, not only as the guidance to the stimulation and stable yields of treating regions, but also played an important role in reservoir reform of other low permeable reservoirs, from which draw the lessons.