亚临界蒸汽驱技术在低渗透油藏中的应用

Near-critical point steam-flooding technology application in low-permeability reservoir

吴永彬 赵欣

WU Yongbin ZHAO Xin

中国石油勘探开发研究院，北京　100083 大庆油田有限责任公司勘探开发研究院，黑龙江大庆　163712

Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China

大庆朝阳沟低渗透油藏普遍存在启动压力高、高含蜡引起常规水驱开采冷伤害严重、注入能力差、产液水平低，天然裂缝及人工压裂裂缝广泛发育导致局部暴性水淹严重、水驱波及体积小等突出问题。为提高该油藏开发效果和采收率，采用室内机理实验与热采数值模拟相结合的方法，剖析水驱冷伤害、裂缝窜流机理及高压亚临界蒸汽驱降低启动压力梯度、熔蜡解堵、蒸馏等提高采收率机理；在精细地质建模及水驱生产动态历史拟合基础上，依据裂缝发育特征及剩余油分布特征，设计出适合该裂缝性低渗透油藏蒸汽驱的矢量井网，并优化出最佳汽驱参数。矿场3个井组试验结果表明，亚临界蒸汽驱可大幅提高水驱裂缝性低渗透油藏开发效果，转汽驱后平均产量是水驱的4倍，预期提高采收率10%以上。

According to problems such as deep cool damage, low capacity of injection and fluid production due to high start-up pressure and high wax content in the process of water-flooding, and serious flooded and low water sweep volume caused by widespread natural and artificial fractures in Chaoyanggou Daqing low-permeability oil field, in order to massively enhance the oil recovery factor so as to realize the high efficient development, approaches of in-house laboratory experiments, reservoir engineering analysis and numerical simulation are utilized to study the mechanisms of enhanced oil recovery by fracture steam-flooding and decreasing start-up pressure gradient, blocking remove by melting wax and distillation. Based on fined geological modeling and production dynamic history fitting, combining with fracture development characteristic and residual oil distribution, the injection capacity of the fluid with different characteristics, effect of fracture system on the sweep efficiency of steam, the optimum well pattern, well spacing and key parameters of injection and production in steam-flooding are designed. The study indicated that the steam-flooding at low permeability reservoir is different from that at heavy oil reservoir. The steam injected at low-permeability reservoir is characterized of high temperature, high pressure, high specific heat enthalpy, low specific volume, low steam quality and the steam is at the near-critical condition. The injected steam effectively reduced the oil viscosity, altered the wettability of reservoir rock, enhanced the oil distillation ratio, lower down the threshold pressure gradient and massively enhanced the production performance of steam-flooding. At present, steam pilot test with 3 well groups has launched and the results are evident.