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

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.