大庆油田三元复合驱过程中垢预测与垢研究

Scale prediction and analysis in ASP combination flooding in Daqing Oilfield

根据大庆油田三元复合驱试验区的地质情况,结合复合驱体系的配方,对复合驱过程中结垢类型进行了分析。垢产生的原因为:①化学剂与地层内流体不配伍直接产生沉淀而结垢;②碱与储层矿物反应后产生的离子与储层流体发生化学反应,导致不配伍的沉淀产生;③流体采出过程中,随着温度和压力的变化,某些物质沉淀结垢。针对这种情况,研究了不同时间(4、36、120、840h)和固/液比(1:0。5、1:1、1:2、1:4)条件下,储层不同矿物组合与单一碱、三元复合体系静态反应后液相体系中的主要离子成分,并利用溶度积法预测出三元复合驱过程中储层结垢类型和结垢强弱顺序。考察了Ca2+、Mg2+、Al3+、SiO44-、CO32-、SO42-、OH-等离子间的配伍性。利用能谱电镜观察化学剂动态驱替实验后的岩心,发现颗粒表面附存有Ca(OH)2垢和非晶态粒间充填的硅酸盐垢。对试验区中心井的产出垢分析表明,垢主要来自钻井液中的微粒,其次来自储层的颗粒。

According to the geological conditions of the ASP flooding area in Daqing Oilfield, and the components of combination flooding system, the scaling types during flooding are analyzed. The scaling reasons can be concluded as 1. Precipitation because of the incompatibility between chemicals and formation fluids; 2. Precipitation because of the reaction between ions from alkaline and reservoir minerals with formation fluids; 3. Precipitation because of temperature and pressure changing during the recovery of fluids. Static experiments are conducted to investigate the main components in the fluid phrase after the reaction of formation minerals with alkali and flooding system, and the scaling types and sequences can be forecasted by solubility. The reaction time varied from 4 to 840 hours, and the ratio of mineral to solution from 1/0. 5 to 1/4. Such kinds of scales as Ca(OH)2 and aluminosilicates are observed on the reservoir cores after ASP flooding tests. Analysis on the scale produced from the ASP flooding center wells shows that they come mainly from the fine solids in drilling fluid and particles from formation.