Research On Improved Recovery Technique Of Steam Flooding For Medium Heavy Oil Reservoir

At present,heavy oil?Bitumen and Tar Sand Oil?accounts for more than 70%in the global remaining oil geological reserves.Steam flooding,as the most effective and the most widely used technique in thermal recovery of heavy oil around the world,mainly applies to the oil reservoirs of heavy or extra-heavy oil with viscosity more than 1000mPa×s.Numerical reservoir simulation is the most efficient method for research of remaining oil distribution,prediction of development index,optimization of injection and production parametric and so on,using computer model to simulate the process of oil-gas field development and history matching of production.For medium heavy oil reservoirs with viscosity less than 500mPa×s,the steam flooding method cannot be referenced as mature practices,due to the difference of remaining oil distribution,reasonable well pattern and optimization of injection and production parametric to the heavy oil that viscosity is more than 1000mPa×s.Based on the M-?block of the M oil field in Kazakhstan,this paper makes a deep analysis of geologic features and development results.Under the numerical reservoir simulation method,and according to dynamic monitoring data and actual production data,this paper studies on remaining oil distribution,development influence factors and its results after steam flooding,optimization of reservoir engineering design,providing the solutions of improving development results and shifting of development method at the middle-late stage and its feasibility.This paper provides the conclusions as follow:?1?Although the application of steam flooding for medium heavy oil has got good results,it has been exposed with problems and contradictions at the same time,such as low steam injection rate,the obvious contradiction between layers,non-uniform progression of steam front,unreasonable well pattern and spacing,low development efficiency caused by thick oil horizon,great difficulty in stable production and so on.?2?The experimental results of rheological properties of medium heavy oil show that when the reservoir temperature is above 60 degrees,the crude oil in the study area is Newtonian fluid,which conforms to Darcy's law.Experiments proved that the oil displacement efficiency of steam flooding is obviously higher than injection of hot water at different temperatures,and the higher the temperature,the higher the displacement efficiency.?3?The main influence factors of steam flooding's effectiveness lie in the geologic aspect?including sedimentary microfacies,effective thickness,faults and edge-bottom water etc.?,as well as in the aspects of development method and reservoir engineering.?4?Reasonable well density is 0.3-0.5 ha/wells,and reasonable well spacing is 73-114m.?5?For medium heavy oil reservoirs with viscosity less than 500mPa×s,steam injection rate shall be no less than 1.0t/?d×ha×m?,the dry degree of steam at the bottom shall be over 30%and production-injection ratio shall be higher than 1.1.?6?The production practice of the well patterns encryption test area shows that the contradiction of the reservoir development plane has been improved,the oil recovery speed is increased by 0.5%,the final recovery rate is up to 43%,and 11%higher compared with the original well patterns.?7?The top reservoir with a thickness of more than 10 m should be avoided,and the steam thermal utilization rate should be fully increased.Stratified steam flooding should be carried out in areas with a total thickness of more than 24m in order to improve sweep efficiency of steam flooding in lower layer.?8?Through demonstration and comparison of alternative technology schemes of steam flooding,the development effect of water-steam alternating slug flooding is superior to that of hot water flooding,intermittent steam flooding and continuous steam flooding.The technology of water-steam alternative injection is recommended as the development mode conversion at the later stage of steam flooding.Through the above research,the next step of steam flooding adjustment and optimization in M-III reservoir has been clarified,that is,at the present stage,the secondary infilling of well pattern should be comprehensively promoted in the plane,the separate layer steam injection should be carried out between layer D₂ and layer J₁ vertically,and the injection-production parameters should be optimized simultaneously.At the later stage of steam flooding,the technology of water-steam alternative injection should be duly convered.The results in this paper can be used as guidance and reference for the development of steam flooding in medium heavy oil reservoirs.