注水水质对海上油藏储层损害影响实验研究

Experimental study on the effect of water injection quality on reservoir damage of offshore reservoir

注水水质与储层岩石及流体的配伍性好坏,直接影响注水井的吸水能力。以海上某一油藏条件为基础,通过理论分析与室内实验的方法,开展了储层伤害机制评价、悬浮物浓度(S)、粒径中值(D)及含油率(O)等注水水质指标对储层损害的实验研究。结果表明:目标油田悬浮物中有机物质占悬浮物绝大部分,多呈聚集体或絮团形式产出,烘干后的絮团粒径粗大可达40μm以上,无机物质占少部分,且无机物质中主要是结垢产物,悬浮物中塑性絮团和刚性颗粒共存。对于中高渗透率储层,水质指标控制在S≤20 mg/L、D≤4μm、O≤35 mg/L,可实现有效的注水开发;而对于高渗透率储层,水质指标控制在S≤15 mg/L、D≤5μm、O≤35 mg/L或者S≤20 mg/L、D≤4μm、O≤40 mg/L范围内,可实现有效的注水开发。

The compatibility of injected water quality with reservoir rock and fluid directly affects the water absorption capacity of water injection wells.Based on the conditions of an offshore reservoir,through the methods of theoretical analysis and laboratory experiment,the evaluation of reservoir damage mechanism and the experimental study of reservoir damage caused by water injection quality indexes such as suspended solids concentration,median particle size and oil content were carried out.Results showed that the organic matter in the suspended solids of the target oilfield accounted for the majority of the suspended solids,which were mostly produced in the form of aggregates or flocs,and the particle size of the dried flocs could reach 40μm,inorganic substances accounted for a small part,inorganic substances were mainly scaling products,plastic flocs and rigid particles coexisted in suspended solids.For medium and high permeability reservoirs,to achieve effective water injection development,the upper limit of water quality indicators was S≤20 mg/L,D≤4μm and O≤35 mg/L.For high permeability reservoirs,water quality indicators was controlled within the range of S≤15 mg/L,D≤5μm,O≤35 mg/L or S≤20 mg/L,D≤4μm,O≤40 mg/L,which could realize effective water injection development.