Research On Multistage Alternating Injection Of Acid Fracturing Technology In Tahe Oil Field

Tahe Oilfield formation has the characteristic of high temperature,high pressure,strong heterogeneity and fracture development.The retention rate of conductivity is only 20%-30% of the initial conductivity and stable production time is short.Fast acid rock reaction and serious filtration of liquid would cause short live acid penetration distance and low conductivity of acid fracture.In this paper,multistage alternating injection of acid fracturing technology in tahe oil field is carried out.There are 4 liquid: fracturing fluid,gelled acid,crosslinked acid,self-generated acid.The rheological properties of the liquid,the compatibility with the formation and the dissolution of the acid solution were studied.Different liquid system combination,injection stage and injection time of each stage have influence on the surface shape of acid fractures and the conductivity.The numerical values were optimized by experiment.The shape of acid fractures and live acid penetration distance are simulated through acid numerical simulation software.By the results of comprehensive experiment and numerical simulation,and considering conductivity and live acid penetration distance,the recommended liquid is: gelled acid + fracturing fluid.When the closing pressure is 70 MPa,the short-term conductivity is 25 D·cm.The injection stage is preferably 4,and the stage injection time is 35 min.By optimizing the liquid combination and parameter optimization of the alternate injection process,the multi-stage alternating acid pressure process suitable for Tahe oilfield is formed to guide the reservoir reconstruction in this area.