低渗储层注水伤害研究

低渗透的宝浪油田是中偏强水敏储层,在进行了各种防膨措施后,注水压力仍不断上升,从25MPa上升至32MPa,依然欠注,即使频繁进行酸化、洗井等增注作业,效果也不理想。文章通过注入水水质分析和控含铁、含氧量进行的模拟地层水岩心流动驱替实验,认为注水造成储层堵塞的真正原因是注入水含铁含氧量偏高。注入水中含铁含氧,形成了Fe(OH)_2、Fe(OH)_3胶体,这类铁氧化合物,或包裹注入水中的固有颗粒,使颗粒粒径增大,形成"软颗粒",或产生新的颗粒,同注入水中的刚性颗粒相互作用,造成储层严重堵塞。即使少量的铁氧化合物,因低渗储层孔喉细小,其造成的堵塞也非常明显,在避免水敏的情况下,驱替120PV时伤害率达37.0%,而常规刚性颗粒堵塞,驱替180PV仅3.4%。所以,该低渗油藏注水开发,不但要防膨和控制注入水的颗粒粒径和颗粒浓度,尤为重要的是控制注入水的含铁、含氧量。

Study of water injection damage in low permeability reservoir

Reservoir belong to medium partial strong water sensitivity in Baolang Oilfield.After carry through different kinds of anti-expansion measure,injected pressure still is continual uprising from 25MPa to 32MPa,effectiveness is not ideal though frequence carried out injection increasing operation such as acidification,washed wells and so on. The article get across water quality analysis of injected water and displacement experiment of core flow with simulation stratum water Which controled iron and oxygen content,it is real reason that reservoir damage is injected water with high iron and oxygen content.Injected water form Fe(OH)_2 and Fe(OH)_3 colloid which wrapping inherence grain and increasing grain size and becoming soft grain,the new grain are interacted with rigidity grain and resulted in stratum serious jam.A little iron and oxygen compound also cause serious jam because subtilis pore and throat. Reservoir damage reach 37.0% when displacemen 120PV without water sensitivity,but conventional rigidity grain only is 3.4% when displacemen 180PV.Water injection development must prevent expansion and control grain size and concentration for low permeability reservoir,especially control iron and oxygen content of water injection.