| Heavy oil fields locate in many places of China, there are also a variety types of heavy oil reservoirs. However, for the oil’s high density, high viscosity, reservoir buried deep and their low permeability in deep areas and their low recovery and employ degree, it bring much trouble for oilfield development and crude oil transportation. For a long time, many experts and scholars paid much attention and did many researches on oilfield development and oil transportation. Thermal recovery technology was used broadly in many oil regions of oil field. Including the mature technology about steam flooding and steam huff and puff which was frequently used for many years, the technology called Steam assisted gravity drainage oil which was under trial and the controversial skill about in-situ combustion. In recent years, Zhong Yuan Petroleum Exploration Bureau has discovered a certain scale of geological reserves of heavy oil in Inner Mongolia acreage, With the in-depth exploration of Inner Mongolia exploration area, new discovery of heavy oil reserves will continue to increase in the near future. Therefore heavy oil development breakthrough is around the corner, how to get a rational exploration and an effective use of these heavy oil reserves will bring an important significant for Zhong Yuan oil field’s stability and sustainable development. For years, the thermal recovery experiments were tested for many times, depending on the comprehensive researches from Sheng Li, Henan and Liao He oil field since 2010,and after many arguments,according to the thought of first break, then optimize", they successively imported the technology of horizontal well thermal recovery from Sheng Li oilfield,vertical Well thermal recovery technology among in thin inter beds of He Nan oil field and their relevant thermal recovery equipment such like supercritical boiler, etc. For different types of heavy oil reservoir, they carried out a variety of composite thermal recovery tests, developing the key technology of thermal recovery in a new progressing stage and got some achievement and cognition in a certain extent. But on the one hand the reservoir conditions are not clear,on the other hand the mechanism research and parameter optimization technique are not perfect, compound of heavy oil steam stimulation test is of great importance to improve economic benefit.There are two main problems, one is that accumulation of researches about compound of heavy oil steam stimulation tests and mechanism studies are not enough, the other one is that the parameters optimization of compound of heavy oil steam stimulation are not exactly especially with the parameter of mixed injection rate of Viscosity reducer for crude oil, nitrogen and carbon dioxide. In order to improve the effect of Inner Mongolia heavy oil development, they carried out this project, counting on the characteristics of heavy oil in Inner Mongolia reservoir, they conducted experiment of mixture with steam stimulation, optimized the steam injection plan of composite stimulation in target blocks, further optimized the injection parameters, forecasted the field’s actual production index, determined the optimal viscosity reducer’s injection rate, the optimizing injection program and the perfect combination of slug injection, eventually formed an effective development policy, improving the economic benefits of target block with compound steam huff and puff.This paper is based on the project of compound heavy oil steam stimulation from Mao 8 block, Cha Gan sag, in Inner Mongolia, researching on laboratory thermal recovery, I carefully analyzed the oil field data,the physical property of crude oil and the different displacement mechanism of each medium. Depending on the study before and searching a wide range of papers and monographs in view of heavy oil development in the domestic and overseas, for the problems we confronted during the actual exploration, for example, the high viscosity and low liquidity of the crude oil, the poor formation heterogeneity and permeability, the uncertain integrating scale usage of viscosity reducer, the CO2,N2 mixed injection optimization and such problems like numerical simulation and etc. Through designing horizontal well laboratory model and processing the thermal experiment of different media injection and analyzing the factors which different types and usages of medium lead to different results in the heavy oil thermal experiment, we analyzed the advantages and disadvantages of different slug combination in the mode, optimized the best mixed proportion, made the transformation of the actual production parameters. It has the significance to improve the ultimate recovery of the reservoir and guide the oilfield’s production.This paper’s research contents and results mainly include the following several aspects:1) the mechanism of displacement of reservoir oil about N2 and CO2 and oil/water soluble viscosity reducer, rational theoretical analysis, the scientific explanation about the phenomena that occur in the experiment.2) This paper introduced the screening condition of the steam stimulation for heavy oil reservoir, analyzed the influence factors of the development in heavy oil reservoir with steam stimulation such as crude oil viscosity and density, reservoir depth and effective thickness, reservoir pressure, original oil saturation and permeability of reservoir boulders, and analyzed the factors on the mechanism of increasing yield of steam stimulation.3) According to the actual situation of oil field’s production, combined with Mao 8 the sixth cycle steam injection geological design data, with the parameters as horizontal well production string’s length, the mine’s actual steam injection rate, the well’s real diffusion radius, the real formation parameters of horizontal Wells, core permeability, core porosity, original oil saturation and formation water property, we designed the laboratory physical simulation model of horizontal wells under the condition of inner room.4)In view of the crude oil’s characteristics of Zhong Yuan oilfield in Inner Mongolia and the viscosity reducer samples, we analyzed the physical properties of the oil and did the oil/water soluble viscosity agent evaluation experiment, we also studied the compound thermal recovery development mode, designed separate steam injection (S), steam+viscosity agent mixed injection (DS), steam+CO2 mixed injection (CS), steam+N2 mixed injection (NS), steam+N2+CO2 mixed injection (CNS), steam+viscosity agent+ CO2 mixed injection (DCS), steam+viscosity reducer+CO2+N2 mixed injection (DCNS) and etc. We also analyzed the different development ways and medium injection on the laboratory model of horizontal well production’s effect, the optimal injection rate under different injection ways, and the optimum program which is perfect.Experiment showed that the mixed injection was better than a single medium injection,steam+CO2 mixed injection was better than steam+N2 mixed injection, the viscosity agent got a poor thermal stability under high temperature and the effect from mixed viscosity injection wasn’t obvious, steam+CO2+N2 mixed injection was better than the steam+CCO2 mixed injection. Four mixed phases’effect was not obvious, the horizontal well’s recovery effect was less efficient.5) The result of the experiment was translated to the parameters of actual production and fitted with the numerical simulation. It provided a datum reference of reasonable development scheme and production technology index.Key technology and main innovation points:1)Physical property analysis of crude oil and laboratory evaluation of oil/water soluble viscosity.2) The physical model design of heavy oil DC/NS steam stimulation experiment.3) Different injection slugs combination and injection parameters optimization. |
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