Research And Application Of Acidizing Technology Of Sandstone Reservoir In Chengdao Oilfield

The Guantao Formation reservoir in Chengdao Oilfield has many oil-bearing series and thin single-layer thickness,which belongs to high porosity and high permeability reservoir with prominent interlayer and intraformational heterogeneity.The block is in the stage of secondary oil recovery with water flooding as the main means.With the extension of water injection cycle,the reservoir seepage capacity decreases,the water injection pressure is high,and the water flooding effect is poor.Conventional acidizing technology can not achieve the effect of deep distance and fine stratification.In order to solve this situation,it is urgent to develop a set of acidizing fluid system and layered acidizing technology suitable for acidizing in this block,so as to improve reservoir porosity and permeability conditions,restore water injection pressure and increase injection production ratio of oilfield.In this paper,the reservoir characteristics and clay minerals of Guantao Formation in Chengdao Oilfield are analyzed,and the reservoir sensitivity evaluation experiment is carried out.It is clear that the main cause of reservoir pollution in Chengdao oilfield is pore roar blockage caused by clay swelling,particle migration and precipitation caused by the incompatibility of external liquid and formation.Through laboratory experiments,static dissolution experiments of different types of clay minerals were carried out at room temperature and 70℃.The dissolution effects of different acid systems on kaolinite,illite,montmorillonite,chlorite and calcium carbonate were determined,and the optimal acid system for different types of clay minerals and carbonate rocks was optimized.The core of Chengdao Oilfield was selected and the single acid solution and combined acid solution dissolution experiments were carried out on the core.A composite acid system was developed with 12%HCl+4%HBF₄ as the pre acid,12%HCl+4%HBF₄+2%HF as the main acid and12%HCl+2%HF as the post acid.The best injection ratio of pre acid,main acid and post acid was determined by core acid flow simulation experiment;On this basis,the advantages and disadvantages of several conventional layered acidizing technologies are studied and analyzed.Combined with the reservoir characteristics of the block and the influencing factors of layered acidizing construction,the integrated layered acidizing and water injection technology with SZSFMB packer and KTP water allocator is optimized and applied in the field.The application results show that after acidizing,the water injection pressure is reduced,the daily water injection is increased,the plugging removal effect is obvious,the water flooding effect is improved,and the economic benefit is increased.It has a good reference and guiding significance for increasing production and injection of other high porosity and high permeability sandstone reservoirs.