The Study Of Geomodeling For The Reservoir Suited For The Carbon Dioxide Flooding

As one of the efficient EOR methods, carbon dioxide has been employed worldwide to flood oil fields, which may be of tight stratums or poorly water-flooded. However it may fail due to anisotropy, high water cut and high permeability layers causing gas coning. Thus it’s necessary for CO₂-driven oilfields to carry out accurate stratum characterization in order to set up 3D geological models for CO₂ injection research before its implementation.Hei59 Block in Daqingzijing Oilfield has been flooded by CO₂ and it was studied in this paper in order to find out the law for CO₂-driven reservoir characterization. Quite a few methods were applied in this research. Analytical hierarchy processing is applied to make a delicate characterization of each single sand body, based on deposition study and high resolution sequence analysis. The combination of depositional energy unit and physical properties analysis was used to determine the most likely gas-breakthrough channels and disclose patterns for sand superposition, deposition and distribution of high permeability layers with gas-coning. Geological 3D model, targeting CO₂ flooding, was finally completed with interactive geological modeling technology. All of these efforts brought forth the results as following:By analyzing the regional deposition background, logging data and core specimen, the framework of isochronal-stratum with high resolution was set up. And a further step was taken to make the formation division.The depositional microfacies type was determined to be delta front subfacies deposition, developing mainly with underwater branch channel and mouth bar. At the same time the well pattern data and sedimentology were used to get a deep understanding of sand bodies. The superposition modes for major reservoirs were found out and the distribution law for sand consistency, geometric conformation and sideline was also acquired.Based on the result of high resolution sequence stratigraphy analysis, four depositional types, such as‘bull’s-head type’submarine branch channel, vertical superposition underwater branch channel, main mouth bar and marginal mouth bar, were setup and the depositional modes for major reservoirs of the objective layers were revealed.A standard for evaluating the most likely gas-coning channels, by means of energy unit classification and reservoir physical properties analysis, was setup, aiming at gas-breakthrough study in single sand. The coning channel with high possibility is mainly subject to depositional microfacies and sand distribution range horizontally while high energy units vertically.The facies controlled random modeling technology was used to build up the stratum geological model, which was then constrained and adjusted by geological study result. The model was eventually completed and suitable for CO₂ flooding study.