Reservoir Damage Assessment And Preventive Measures In Water Injection Wells

Zao32 block is located in Zilaitun Development Zone of Zaoyuan oilfield,which is located in the north of Dagang Oilfield.It has experienced four stages since producted:natural energy exploitation,well pattern establishment,low speed and low efficiency,and edge expansion adjustment.The reservoir of this block has been damaged in the process of waterflooding development.The main manifestations of reservoir damage are the decrease of permeability and the increase of injection pressure,resulting in the decline in oilfield production,affecting the recovery of this area.How to reduce the damage to the reservoir of water injection well and put forward reasonable prevention and control measures are the main research direction of water injection development.Base on the geological characteristics of Zao32 block,reservoir physical properties and fluid characteristics,this paper evaluates and analyzes the damage of water injection well reservoir through experiments,putting forward prevention and improvement measures.The main research contents:reservoir physical properties and pore structure;reservoir distribution characteristics and fluid properties;sensitivity evaluation of water injection well reservoir;The critical flow rate and reasonable water injection speed of injected water are determined by velocity sensitivity experiment evaluation and analysis;The reasonable water injection salinity of the reservoir is determined by water sensitivity experiment evaluation and salinity sensitivity experiment evaluation;The degree of acid and alkaline sensitivity damage are determined by acid and alkaline sensitivity damage evaluation and reverse experiments.The stress sensitivity damage degree is determined by stress sensitivity experiments.Evaluate and analyze the water quality of the injection water in Zao 32block,carrying out relevant experiments in terms of the median particle size of the solid suspended particles,the concentration of the solid suspended solids,the oil content of the injected water,the corrosion performance of the injected water and bacteria.Analyze the influence of various factors on reservoir damage,and finally get the injection water quality index suitable for the reservoir.Finally,prevention measures are proposed according to the reservoir characteristics of the Zao 32 block.The appropriate clay stabilizer“2%NH₄Cl+3%Polyglycolamine”is selected through the crushing rate determination experiment and the expansion rate determination experiment.The acid/rock dissolution rate experiment and the core acidification experiment are used to select a suitable acid compositions“12%HCI+l%HF”.It reduces reservoir sensitivity damage effectively and achieve the purpose of improving oil field recovery by proposing suitable injection water quality indicators,screening out the best clay stabilizer compositions and acid compositions.