姬塬油田注入水与地层水配伍性研究

姬塬长8储层在采用清水进行注水开发过程中,存在注水压力高、吸水指数低、注水见效慢、注采严重失衡等问题,严重影响油田开发效果。本文在对该区块注入水、地层产出水组成分析的基础上,将结垢趋势预测和室内模拟实验相结合,详细分析评价了注入水与地层水的配伍性。配伍性实验结果表明:姬塬长8储层地层水为CaCl2水型、注入水为Na2SO4水型;地层水与注入水以任意比例混合后,在30℃下均无垢生成,80℃下均产生了碳酸钙结垢而无硫酸钙垢形成。结垢趋势预测结果表明:在30℃下地层水与注入水混合后基本不生成碳酸钙垢;在50℃下,随着地层水比例的增加,碳酸钙结垢趋势增加,当地层水与注入水之比为4∶6 10∶0时,显示会有碳酸钙垢生成;在80℃下,碳酸钙垢趋势明显增加,地层水与注入水以任意比例混合后均会产生碳酸钙垢;在30℃、50℃、80℃下地层水与注入水以任意比例混合后均无硫酸钙垢结垢趋势存在。综上所述,姬塬长8储层注入水与地层水配伍性差、结垢是造成姬塬长8储层注水压力高的主要原因之一。

Study on Compatibility between Formation Water and Injection Water in Jiyuan Oilfield

There existed many problems,such as high pressure of water injection wells,low water absorption index,slow effect block injection,water imbalance,etc,during surface water injection process in the eighth reservoir of Jiyuan oilfield.On basis of the analysis of the injective water and formation water quality,the compatibility of the injective water and formation water was studied by the scaling prediction and laboratory simulation method.The experimental results showed that the formation water was CaCl2 type,and the injective water was Na2SO4 type in Jiyuan oilfield.When mixing the formation water and the injective water in different proportions,there was not scale to form at 30℃,whereas,calcium carbonate scale deposits occurred at 80℃(formation temperature).The scaling prediction results showed that the calcium carbonate scale did not occur at 30℃,meanwhile,with the increase of the proportion of formation water,calcium carbonate scaling tendency increased at 50℃.When the ratio of the formation water and injection water was 4∶ 6—10∶ 0,calcium carbonate scale deposit would form at 50℃.Furthermore,the calcium carbonate scale tendency increased at 80℃,scale deposite occurred in any proportion of the formation water to injection water.The IS scaling prediction results showed that calcium sulfate scale did not occur when the formation water and the injective water mixed at any ratio at 30—80℃.All mentioned above showed that the poor compatibility and the scale of injected water and formation water was the main reasons caused high pressure of water injection wells in the eighth reservoir of Jiyuan oilfield.