青海油田尕斯N–N超高盐油藏复合驱提高采收率技术

Oil Recovery Enhancement by Composite Flooding Technology for Gasi N–N Ultra-High-Salinity Reservoir in Qinghai Oilfield

贾志伟 程长坤 朱秀雨 濮兰天 韩宇 扈福堂

JIA Zhiwei CHENG Changkun ZHU Xiuyu PU Lantian HAN Yu HU Futang

中国石油青海油田分公司钻采工艺研究院，甘肃敦煌 736202 中国石油青海油田分公司采油二厂，甘肃敦煌 736202

Drilling and Production Technology Research Institute, PetroChina Qinghai Oilfield Company, Dunhuang, Gansu, 736202, China The No.2 Oil Production Plant, PetroChina Qinghai Oilfield Company, Dunhuang, Gansu, 736202, China

青海油田尕斯N1–N21油藏的地层水矿化度和钙镁离子含量超高，进行凝胶与表面活性剂复合驱，常规凝胶易脱水破胶，长期稳定性差，同时常规表面活性剂易与地层水中的钙镁离子发生反应产生沉淀。针对前一问题，合成了适用于尕斯N1–N21油藏的抗高盐有机凝胶，配方为0.3%～0.4%聚合物+0.2%～0.3%交联剂+0.1%～0.2%稳定剂，该体系在68 ℃条件下初凝时间大于70 h，成胶后凝胶黏度大于1.0×104 mPa∙s；优选了抗高盐表面活性剂QH-1，评价了界面张力和驱油效果，发现质量分数0.4%的QH-1溶液可提高采收率18.72%。室内试验结果表明，交替注入抗高盐有机凝胶和QH-1能有效遏制水的无效循环，提高中低渗区域的驱油效率，优化的“凝胶+QH-1”复合驱可提高采收率27.6%以上。该复合驱在尕斯N1–N21油藏9口注水井进行了应用，应用后对应油井的平均含水率由80%降至70%，增产油量2.41×104 t。研究结果表明，“凝胶+QH-1”复合驱提高采收率技术对青海油田尕斯N1–N21超高盐油藏增油降水具有很好的效果，具有推广价值。

The salinity and the content of calcium and magnesium ions are ultra-high in the formation water of Gasi N1–N21 reservoir in Qinghai Oilfield. While using gel and surfactant composite flooding, conventional gels are prone to dehydrate and break, showing poor long-term stability. Meanwhile, conventional surfactants are easy to react with the calcium and magnesium ions in formation water to cause precipitation. In view of this, a high-salinity-resistant organogel suitable for Gasi N1–N21 reservoir was developed, which consisted of polymer (0.3%–0.4%) + crosslinking agent (0.2%–0.3%) + stabilizer (0.1%–0.2%). The initial setting time of the system was longer than 70 h at 68 ℃, and the viscosity after gelling was greater than 1.0×104 mPa·s. What's more, a high-salinity-resistant surfactant QH-1 was optimized, and the interfacial tension and oil displacement effect were evaluated, witha finding that the QH-1 solution with a mass fraction of 0.4% could enhance the oil recovery by 18.72%. The laboratory test results indicated that alternate injection of the high-salinity-resistant organogel and QH-1 could effectively curb the ineffective water circulation and improve the oil displacement efficiency in the low and medium permeability areas. Notably, the optimized “gel + QH-1” composite flooding was capable of enhancing oil recovery by more than 27.6%. The composite flooding was applied to 9 water-injection wells in Gasi N1–N21 reservoir. As a result, the average water cut of these oil wells decreased from 80% to 70%, and the oil production increased by 2.41 × 104 t. The research results show that the oil recovery enhancement by “gel + QH-1” composite flooding is effective in enhancing oil production and decreasing water cut in Gasi N1–N21 ultra-high-salinity reservoir, so it is worthy of promotion and application.

中国石油重大科技专项“柴达木盆地老油区精细调整及提高采收率关键技术研究”(编号：2016E-0104)部分研究内容

https://doi.org/10.11911/syztjs.2021121