Study On Reservoir Protection Technology In Water Injection Process Of Shahejie Formation In Zhangdong

The properties of low permeability reservoir are characterized by its strong heterogeneity, complex pore structure, high content of clay minerals, and weak ability bearing reservoir damage, which brings many technical problems to development process. Especially in the water injection development, due to the insufficient resource of injected water, the way adopting waste water reinjection to supplement the formation energy has been one of the stimulating methods. The produced waste water is characterized by high content of suspended material, strong corrosivity, and low salinity. Once the waste water is injected into formation, it will mix with formation water initiating a series of damage problem, such as choke, scaling and corrosion, which decreases the injection and influences the water sorption ability and displacement efficiency. Moreover, there are some problems, such as the difficulty of water injection, high pressure of water injection, in the production.Taking the main strata of DaGang oilfield ZhangDong development area----shahejie strata for instance, based on further understanding of reservoir geology, this paper reports the damage mechanisms and type in water injection process combined with sensitivity experiment and the evaluate of compatibility of injected water, according to the in-situ monitoring of the water quality. Then this paper propose the targted formation damage control measure and augmented injection measure for injection well, which provides case for highly efficient exploitation of low permeability reservoirs. The results obtained by the paper:(1) The lithology of Zhang-dong development area’s main producing strata, namely ShaHeJie group, is feldspathic lithic sandstone with moderate porosity and low permeability. Secondary intergranular pore dominates the strata. The absolute content of clay mineral is more than10%,in which kaolinite and illite/montmorillonite layer dominate.(2) The result demonstrates that injected water’s oil content in zhangdong development area meets the standard, however, the corrosion rate and the suspended solids exceed. Moreover, there are low-grade CaCO3scaling with the formation water; Combining with the result of sensitivity evaluate diagnoses that main damage mechanisms and types in water injection process include outside solid-phase particle choke、the medium water sensitive、the medium-weak speed sensitive、corrosion and scaling.(3) This paper optimizes the water injection system and reservoir damage control measure, and also proposes the reasonable water injection volume、anti-swelling agents protecting reservoir and it’s injection parameters, which achives good practive effect in the field. At the same time, this paper recommends some augmented injection method for zhangdong development area.According to the study of ZhangDong Development Shahejie group, this paper form a research method and evaluation system of formation damage mechanisms and protect techniques in water injection process for low permeability reservoir.From the field data, the parameters of injection wells has been increased, and the protection effect is significant, which is suitable for extending in other similar field such as Dagang.