Study On The Acidizing Technology Of Water Injection Well In S Oilfield Sandstone Reservoir

S oilfield is the largest self-managed offshore oil field in our country,the reservoir of S oilfield is the sandstone reservoir,which has the characteristics of high permeability,high porosity,loose cementation and strong sensitivity.The oil field adopts the water injection development mode,and the high efficiency water injection is the foundation of the stable production in the oilfield.Therefore,injecting enough water and effective water injection for injection wells is the key to ensure efficient exploitation of oilfield.Due to the limited capacity of water treatment process in offshore oilfield,it is difficult to inject quality water,which causes the injection wells to be vulnerable and cannot achieve the demand of water injection development.Acidizing technology is one of the main means of injection wells to remove formation damage,which can remove formation damage near wellbore,so as to achieve the purpose of the reducing injection pressure and increasing injection rate.In the process of production,due to the large amount of single well injection and water quality is not stable,lead to amplifying the damage and shortening the effective cycle of the acid stimulation.The acid stimulation of water injection well in the target area is increasing,and most of the wells have reacidizing operation,but the effect of the stimulation is worse and worse.Therefore,in order to improve the effect of injection and prolong the acid treatment period,the acid solution system and process method of acidizing of the injection wells in the target area need to be studied.The paper is mainly focused on the following aspects:(1)By systematic analyzing of oilfield data,laboratory tests and injection-production status,revealing the reservoir characteristics,the types of evaluation of potential reservoir damage factors and the degree of sensitivity,clearing the inherent relationship between reservoir characteristics and formation damage factors;(2)Through the systematic laboratory experiments and testing methods,injection water in the target area,a variety of damage substances,and various corrosion were analyzed.The reason for reacidizing well damage was defined,which provided the basis for the study of the acid fluid system;(3)Using numerical analysis and simulation methods,defined the solid-phase damage pattern,deduced damage radius calculation model and permeability distribution model,and drawn the map of damage scope,providing a strong basis for the optimization of acid stimulation;(4)Through a large number of acid corrosion experiments,analysis of rock samples and the acid residue,acid fluid were preliminary optimized;(5)Through a series of additive experiments,a suitable additive was selected to form a formulation acid fluid.core flow experiments were carried out to evaluate the effectiveness of the formulated acid fluid,and the acid job process and parameters were optimized to provide strong support for the acid stimulation of the oil field.In this paper,the cause of the damage of the injection wells reservoir was clarified,and a strong and reliable acid system was formed to provide effective technical support for the effective injection,the production capacity of the single well and the acceleration of the oil production rate.The research results of this paper have certain guiding significance for acidizing of sandstone reservoirs in injection wells.