海上稠油冷采井多元热流体吞吐堵塞机理及活性油解堵

Blocking mechanism of multicomponent thermal fluid huff-and-puff and unblocking with surfactant oil in offshore heavy oil cold production wells

渤海南堡油田稠油冷采井采用温度低于150℃的多元热流体吞吐开采,吞吐开采后地层堵塞严重,甚至导致油井不出液。通过室内实验分析了地层堵塞原因,明确了注入水与地下稠油乳化后会使稠油黏度增大,乳滴(聚集体)通过孔喉的液阻效应增强导致“启动压力”提高,当乳化区驱替压力低于启动压力时地层出现堵塞;开展了掺稀降黏和活性剂辅助降黏降阻实验,按3∶1∶1的摩尔比配制了由脂肪醇聚氧乙烯醚羟丙基磺酸钠、十二烷基三甲基铵盐和琥珀磺酸钠组成的活性油解堵体系,加入2%该体系后的稀油与含水50%稠油按照稀稠比2∶8混合后,其黏度相较含水50%稠油(7698 mPa·s)降低了98.5%,界面张力相较稠油-水(21.86 mN/m)降低了74.5%,同时乳化区启动压力降至1.86 MPa;通过数值模拟实验,优化了稀油注入量和活性剂质量分数,预测注入2000 m^(3)稀油并在1000 m^(3)前置稀油中加入2%活性剂可实现乳化区解堵,净增油量为4016.5 m^(3)。现场试验表明,解堵后油井日产油5.9 m^(3)/d,累计增油980.7 m^(3),解堵增产效果明显。该技术对海上稠油冷采井解堵和增产具有指导作用。

In Nanpu Oilfield of the Bohai Sea,heavy oil cold production wells are produced using multicomponent thermal fluid huff-and-puff with temperatures below 150°C.However,severe reservoir plugging occurs after huff-and-puff,leading to decreased or halted oil production.Through laboratory experiments on the causes of reservoir plugging,it was clarified that the viscosity of heavy oil increases after emulsification with injected water,enhancing the liquid resistance effect of droplets(aggregates)passing through pore throats,thereby increasing the“startup pressure”.When the displacement pressure in the emulsification zone is lower than the startup pressure,reservoir plugging occurs.Experiments were conducted on dilution and viscosity reduction using an surfactant oil unblocking system composed of fatty alcohol polyoxyethylene ether sodium hydroxypropyl sulfonate,dodecyl trimethylammonium salt and sodium succinesulfonate in a molar ratio of 3∶1∶1.After adding 2%of this system,the diluted oil and the heavy oil containing 50%water were mixed according to the dilution-heavy ratio of 2∶8.Compared with the heavy oil containing 50%water(7698 mPa·s),the viscosity was reduced by 98.5%,and the interfacial tension was reduced by 74.5%compared with that of the heavy oil and water(21.86 mN/m).In addition,the starting pressure of the emulsification zone was reduced to 1.86 MPa.Through numerical simulation,the injection volume of diluted oil and the surfactant concentration were optimized,predicting that injecting 2000 m^(3)of diluted oil and adding 2%of the surfactant to the first 1000 m^(3)of diluted oil could achieve unblocking in the emulsification zone,resulting in a net oil increase of 4016.5 m^(3).Field tests show that after unblocking a well,the daily oil production reached 5.9 m^(3)/d,with a cumulative oil increase of 980.7 m^(3),indicating a significant unblocking and production increase effect.This technology provides a guidance for plugging removal and increasing oil production in offshore heavy oil cold production wells.