Technical Studies On Polymer Flooding Of Being Back To Reservoirs For Sub-layers And Third Type Of Layers In Daqing Oilfield

At present, Daqing Oilfield has entered the high-water cut stage of the development. And since 1995, the polymer flooding has become the enhanced oil recovery technology commonly used by the oilfields which are high water-cut in Daqing. The potential reserves of increasing is gradually reduced along with the main zone of polymer flooding area is expanding. According to the problem of remaining recoverable reserves in the main reservoir is decreasing year after year, the sub-layers and third type of layers must be exploited by the polymer flooding to achieve the potential yield of succeeding. However, these sub-layers are different from the main oil reservoir which is characterized by vertical layers, variable in-phasing, serious heterogeneity, the differences in the larger non-homogeneous reservoir with a general division, which combined a layer of development, shows that the inelasticity seriously affected the development effect. In order to solve this problem, we must further subdivide the reservoir type, unify the standard of reservoir, determine a reasonable producer-injector spacing , the combination of series of strata and the injection parameters and methods to obtain the fine adjustment of oilfield development plan during the tertiary phase.The sedimentary characteristics, reservoir heterogeneity, the interwell communication of sand are carefully studied for sub-layers from the oil field test and fine geological research results in this paper. The injection parameters, a reasonable producer-injector spacing and the combination of series of strata are identified preliminarily to adapt the poor and thin oil sandwich of sub-layers and third type of layers. The clear understanding for reservoir physical characteristics of the distributions are gained. And the reasonable producer-injector spacing, the combination methods for series of strata and the injection parameters are determined as viewed from the tertiary oil recovery.The results show that the main zone has become deterioration gradually from the north direction to the south; and the reserves is reduced from the distribution of the reservoir thickness. The producer-injector spacing of sub-layers and third type of layers should be 150m-175m and 100m-125m respectively by the transition fromâ… A reservoir toâ… B reservoir. The combination of series of strata of sub-layers should be a group as a unit of sandstone to ensure that two layers of the spacer layers are relatively stable. The same layer of the reservoir within the geological conditions should be similar to guarantee the sudden coefficient is less than 3.0, so that the same molecular weight polymer can be injected into the small layer of more than 70 per cent. And the well section of exploitation should not be too long and 40-60 m is more appropriate; the upper and lower limit is ranged from 6m to 8m.In addition, the enhanced oil recovery technologies are developed with polymer flooding based on the problem of the difference between physical characteristics and pressure differences of sub-layers and third type of layers, as well as the geological conditions of more thin and poor layers in the issue. Therefore, the problem of injection effects is solved commendably and the supporting technologies of development are more completely formed for the thin and poor layers. The technology popularization and application of the tertiary oil recovery are provided with a powerful theoretical and technical support for the sub-layers and third type of layers.The field test results show that it is feasible to apply polymer waterflooding to the sub-layers and third type of layers. Moreover, its economic efficiency is better than industry standards.