Abstract
Water channeling of fractured carbonate rocks seriously restricts oil well production and is particularly prominent in the Troyes oilfield, located in the north of Kazakhstan. A nanometer particulate matter (PM) solution was used to evaluate the plugging ability of matrix and fractured core in a fractured carbonate model. Results showed that PM had good dispersion and swelling ability in simulated formation water. The swelling rate reached more than 300% in 3 d. PM had a perfect deep plugging effect in both matrix core and fractured core. The residual resistance coefficient of matrix and fractured core after plugging reached between 3.29 and 5.88, and the plugging rate was between 69.58% and 83.01%. The higher the residual resistance coefficient, the higher the plugging rate. PM has a good selective plugging effect on oil/water. The oil/water selection coefficient Rw/o was less than 1.0 and close to 0, mainly because of the different mechanisms of oil/water and PM. Scanning electron microscope (SEM) imaging results showed that the plugging mechanism of PM in the throat and fractures was manifested mainly in three aspects: adsorptive retention, mechanical trapping, and agglomeration plugging. The mechanism was further verified by energy disperse spectroscopy (EDS) elemental analysis technology.
概要
目 的
对聚合物微球(PM)在碳酸盐岩基质岩心与裂缝 型岩心中封堵效果和油/水选择性进行综合评价。
创新点
1. 制作裂缝型碳酸盐岩模型并进行等效缝宽度计 算;2. 显微评价PM 的水化膨胀特性;3. 进行聚 合物微球深层封堵性能评价;4. 进行聚合物微球 油/水选择性封堵评估。
方 法
采用纳米级聚合物微球溶液,并以哈萨克斯坦北 特鲁瓦裂缝型碳酸盐岩油藏储层温度(54 °C)和 碳酸盐岩天然裂缝尺寸(0.02~0.03 mm)为实验 条件;通过碳酸盐岩裂缝型岩心模型制作、PM 基本性能测试、岩心流动实验以及扫描式电子显 微镜(SEM)和能谱分析仪(EDS)等微观手段, 对PM 在碳酸盐岩基质岩心与裂缝型岩心中封堵 效果和油/水选择性进行综合评价。
结 论
1. PM 在水中具有良好的分散性和溶胀能力,3 d 溶胀率高达300%以上,且对高矿化度盐水具有 较强的耐受性。2. PM 在基质岩心和裂缝型岩心 均具有较好的深部封堵效果;30 cm 长岩心模型 封堵实验表明,封堵后的分段压降均匀分布,岩 心基质和裂缝型岩心封堵后的残余阻力系数介 于3.29~5.88,封堵率介于69.58%~83.01%,且残 余阻力系数越大,封堵率越高;PM 在岩心中水 化膨胀后可形成有效封堵,且平均封堵率高达 70%以上。3. PM封堵的油/水选择系数Rw/o 均小 于1.0 且接近于0,说明PM 具有较强的油/水选 择性封堵效果;这主要是因为油/水与PM 作用机 理不同;PM 遇水后溶胀且表面粘性增加而粘连 在碳酸盐岩壁面,并且不同微球之间相互团聚形 成较大体积的颗粒,因此增加了对注入水的封堵 效果;PM 在煤油中则性能稳定,不产生溶胀和 粘连效果,因此对反向注入煤油具有较低的封堵 效果。4. SEM 成像结果分析认为,PM 在岩心喉 道或天然微裂缝中的封堵机理主要包括三个方 面:(1)PM 单体在岩石颗粒表面吸附,降低喉 道的尺寸,同时多个单颗粒小球增大了层内比表 面积、降低了层内渗透率;(2)PM 溶胀后在小 尺寸孔道形成了机械捕集;(3)多个PM 单体颗 粒团聚成网状结构堵塞了大孔道。EDS 元素分析 技术进一步验证了其作用机理。
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Conceptualization, Jie WANG and Fu-jian ZHOU; methodology, Jun-jian LI; formal analysis and validation, Kai YANG and Lu-feng ZHANG; funding acquisition, Fu-jian ZHOU; writing of original draft, Jie WANG and Fan FAN; review and editing, Fu-jian ZHOU.
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Jie WANG, Fu-jian ZHOU, Jun-jian LI, Kai YANG, Lu-feng ZHANG, and Fan FAN declare that they have no conflict of interest.
Project supported by the Foundation of State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum at Beijing (No. PRP/indep-4-1314), the Science Foundations of China University of Petroleum at Beijing (No. 462014YJRC015), and the National Science and Technology Major Project of China (No. 2015ZX05051003)
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Wang, J., Zhou, Fj., Li, Jj. et al. Evaluation of the oil/water selective plugging performance of nano-polymer microspheres in fractured carbonate reservoirs. J. Zhejiang Univ. Sci. A 20, 714–726 (2019). https://doi.org/10.1631/jzus.A1900249
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DOI: https://doi.org/10.1631/jzus.A1900249