Preparation and Evaluation of a Temporary Plugging Organosilicon Diverting Agent for Fracturing Fluids
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摘要: 压裂现用颗粒暂堵剂多以刚性颗粒为主,现场实施过程中存在压力升高不明显,稳压时间短,应力不能有效转移的难题。通过引入一种有机硅疏水单体,以丙烯酰胺、N,N-亚甲基双丙烯酰胺为主要原料,胶束聚合了一种有机硅水凝胶。考察了不同聚合单体浓度、疏水单体、聚合方法、聚合条件等对LYB聚合物水凝胶的影响,并采用FTIR和元素分析仪对LYB聚合物进行表征。结果显示,LYB聚合物水凝胶的最佳合成工艺:水溶性单体浓度8~10%,有机硅浓度2%,交联剂浓度0.02%,引发剂加量0.2%,反应温度为50~60℃,反应时间为6~8 h。评价了暂堵剂的吸水膨胀、耐盐性、抗剪切、变形性和热降解性。与常规刚性颗粒相比,具有更强抗剪切性、耐盐性和弹性的优势。基于压裂施工曲线和微震监测结果:LYB 暂堵剂到位后,现场起压7~8 MPa, 暂堵后,相同施工压力下,施工排量下降1.5 m3/min, 并通过井下微地震,进一步验证了LYB裂缝转向的有效性。Abstract: Particulate temporary plugging agents presently used in fracturing fluids are mostly rigid, and deficiencies exist in using these plugging agents, such as insignificant pressure buildup, short pressure stabilization time and inability to effectively transfer stress etc. To deal with these problems, an organosilicon hydrogel named LYB was developed through micellar polymerization with main raw materials acrylamide and N,N-methylene bis-acrylamide, as well as an organosilicon hydrophobic monomer. The effects of the monomer concentration, the hydrophobic monomer, the polymerization method and the polymerization conditions on the LYB hydrogel were investigated, and FTIR and element analysis method were used to characterize the LYB hydrogel. The experimental results show that the optimum conditions for the synthesis of the LYB hydrogel are as follows: the concentrations of the water soluble monomers, the organosilicon, the crosslinking agent and the initiator are 8 – 10%, 2%, 0.02% and 0.2%, respectively, the reaction temperature is 50 – 60 °C, and the reaction time is 6 – 8 h. Laboratory evaluation of the LYB hydrogel shows that compared with the commonly used rigid particulates, the LYB hydrogel has higher shear strength, better salt resistance and elasticity. From the fracturing job curves and microseismical monitoring results, it can be seen that when the LYB temporary plugging agents are in place, the in-situ pressure is increased by 7 – 8 MPa. After temporarily plugging the fractures, the flowrate at the same job pressure is reduced by 1.5 m3/min. Using downhole microseisms, the effectiveness of the fracture diversion by the LYB hydrogel is further verified.
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表 1 不同表面活性剂对胶束共聚反应的影响
Table 1. The influence of different surfactants on micellar polymerization reaction
表面活性剂 水溶液乳化和分散后的状态 溶液的均匀
性、稳定性水凝胶的外观 无 加入有机硅后出现分层现象 — — 十二烷基苯磺酸钠 — — — 吐温80 均匀水溶液 均匀、稳定 聚合快,水凝胶中
有少量块状凝聚物十二烷基苯磺酸钠、吐温80 均匀水溶液 均匀、稳定 水凝胶均匀透明,
无凝聚物。表 2 元素分析结果
Table 2. Chemical element analysis results
元素 质量分数% 摩尔分数% 碳(C) 51.13 57.35 氮(N) 18.92 18.20 氧(O) 27.84 23.45 硅(Si) 2.10 1.01 表 3 LYB凝胶单轴力学实验结果
Table 3. Uniaxial mechanics experimental result of QBZU hydrogel
直径/mm 长度/mm 杨氏模量/ MPa 泊松比 24 49 80 0.48 表 4 G-P7井暂堵前后施工参数对比
Table 4. :Comparison of construction parameters before and after temporary plugging of Gao-Ping 7 well
序号 暂堵起
压/MPa暂堵前 暂堵后 施工压力/
MPa排量/
m3/min施工压力/
MPa排量/
m3/min第8段 7 60~62 14 60~62 12.5 第10段 8 60~62 11 60~62 9.5 -
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