Laboratory Experiment And Oil Displacement Mechanism Of In-situ Combustion

As an obvious advanced and favorable oil recovery technique, in-situ combustion has the advantage of wide reservoir adaptation, sufficient material resource, high recovery ratio, low cost. Because very complex oil displacement mechanism, it has much problem on reservoir engineering design and field dynamic mange, for example, there was poor recognition in combustion and oil displacement in reservoir bed, and it was very difficult to judge combustion situation and monitor/control combustion front. So it was very necessity to develop laboratory experiment and research oil displacement mechanism of in-situ combustion.The reasonable similarity criterion was based on scaled physical simulation. The similarity criteria that foreign scholar suggested was simplified combustion situation and omitted kinetics of combustion reaction, owing to very complex oil displacement mechanism, if kinetics of combustion reaction was omitted, there was very difficult to mechanism recognition, effect predication and parameter optimization. On the base of integrated research of combustion characteristic, a new ISC similarity criterion was built that it owned four phases and seven components mathematical mode, established a dynamic model of in-situ combustion process and the ratio of oxygen consumption rate and oxygen transport rate. The involved affecting factors of ISC similarity criterion were the most comprehensive up to now.The most effective method that researched combustion and oil displacement underground was ISC scaled physical simulation. In view of low pressure and small size of existing model, A suit big multi-purpose ISC scaled physical model system was developed independent. This system had very high technical description that the maximum pressure was 15MPa, the maximum temperature was 1000℃,it could be used researched multiwell and multimode ISC physical simulation, its technology and function attained to international improved level.The physical simulation experimental method was found that many technique problems were resolved such as oil layer ignition, gas injection operation and control, complex gas analysis, crude oil character upgrade, and through this method, many ISC physical simulation experiments were developed. The method laid the foundation for the oil displacement mechanism research. Different block crude oil such as Shul138-330 Well super heavy oil, Gao3-2-75 Well normal heavy oil, Len 37-45-562 Well natural oil sand, GaoJian 1 Well natural oil sand was used developing ISC physical simulation experiment. The combustion characteristic was researched, and combustion index such as ignition temperature, air flux, oxygen use factor, apparent H/C atomic ratio was analyzed, combustion front driving rate about different block crude oil was compared, and ISC displacement efficiency was predicted.Through scaled physical simulation experiments, temperature field development In the process of combustion drive and pattern of combustion district was researched, combustion sweep condition and displacement characteristics under the influence of different thickness was investigated, the production operation and control method that could be improved combustion sweep condition was attempted. in addition, A new chemical compound that could be reflected ISC mechanism was discovered in the experiment,which could be revealed reasons that crude oil viscosity upgraded and density decreased.The results of the paper could be provided assured basis for field test programming of Gao3-6-18 Block and Len 41Bolck and reasonable implementation of the scene.