Study On Acidification And Infiltration Enhancement For Low Physical Segment In SAGD Of Heavy Oil

Heavy oil has been excavated as an important geological reserve,but because of its high viscosity,high density and poor fluidity,it is difficult to exploit.During the recent years,it has been found that using SAGD technology can solve the problem of heavy oil extraction,but the pilot test has found that there are many sets of low physical sections,which results in the blocking of the overlying steam cavity,and the development of high water content and low oil quantity in the well group can not discharge heavy oil into the production well by steam action,which brings out a strong impact on the production efficiency.Therefore,it is imperative to solve the problem of blocked up of steam cavity caused by many low physical segments.This paper takes the low physical section of L oil field D84 block G reservoir as the research object,uses scanning electron microscope to detect the mineral composition of reservoir,carries on the reservoir sensitivity evaluation to the target block,according to these parameters and the test result,preliminarily judges the system structure of acidified working fluid.A system of acidified working fluid adapted to the regional temperature,p H value and mineral content of the target low physical segment was developed through laboratory experiments,and its enhanced seepage effect was evaluated.The results show that the reservoir in the low physical section of the target block is weak sensitivity,weak salt sensitivity and extremely strong acid sensitivity.Then the main acid and additives of acidizing working fluid system are selected,and the formula of acidizing working fluid is 4%HCl+2%LSDJ+5%HBF₄+4%acetic acid+2%ethanol+1%NG clay stabilizer+1.5%Lan826+3%ATMP+1%LSNSJ+0.3%EDTA sodium salt+1.5%citric acid+1.5%2-butoxy ethanol,which dissolution rate is 27.65%.The prominent reaction time was 24h.A series of comprehensive evaluation were carried out,such as dissolution,clay stability,corrosion inhibition,chelating property,acid slag inhibition property,etc.The results showed that the infiltration range of the selected acid system was 39.93%?57.06%,which indicated that the acidizing working fluid formula had better acidification and infiltration effect for low physical section natural core.At the same time,this paper puts forward a new seepage enhancement scheme based on low physical section of acid vapor dissolution,and carries out core experiments of low physical section of acid vapor dissolution using the self-developed experimental device of acid vapor dissolution in natural rock ventricle.The range of seepage enhancement of acid-liquid formula developed in this paper is 24.84%?53.12%.According to the reservoir parameters of target block,the relevant parameters of acidizing construction are designed.By simulating the distribution of acid solution,acid steam concentration and porosity by COMSOL software,it is proved that both acid injection methods can meet the expected effect of actual acid injection.Through the combination of laboratory experiment and software simulation,this paper provides new ideas for the research of acidizing and increasing technology and crude oil exploitation in low physical region.