A Study Of Industrialized Polymer Flood Scheme Drafting In Second Type Oil Layers Reservoirs Of Daqing Oil Field

Since the 1990s, Daqing oilfield entered a new development stage of high water-cut, high cost and high development difficulty. There is less residual oil remaining in conventional productive reservoirs, thus an inadequate oil reserve as well as a lower productivity prospect is seen in the period of the eleventh five year plan. Under this condition, we performed a research in eastern N-1-2P block, where tertiary recovery failed to produce sufficiently and we have to move industrialized polymer flood up to the poor and thin layers, so as to ensure a desirable production rate and a sustainable oilfield development.The N-1-2P block lies in the north of the Sartu oilfield, Daqing. It covers an oil containing area of 7 km2. In January 2002 tertiary recovery ended in the conventional productive reservoirs and went up to the poor and thin layers of Sa II10-Sa III10. A total number of 208 wells including producers and water injectors were put into production in December, 2003. Its target layer is a series of fluvial and deltaic deposited reservoir, containing 20 deposited single layers. The deposited sandstone style including fluvial channel sand, crevasse channel sand, interstream sand, interstream silt, under water distributary channel sand, delta front sheet sand and etc. Since the reservoir heterogeneity usually result in irregular water flooding and irregular residual oil distribution during the water flood development period, where is regarded as the poor and thin layer compared with the conventional productive reservoir, thus provide a substantial basis for polymer flood.Polymer solution is a kind of non-newtonian fluid with a specific rheological property. Polymer solution shows a shearing and thinning rhelogical property under low flow velocity; it shows a swelling property at a certain higher flow velocity; if the flow velocity is trmendously high, it shears and degrades polymer solution. Polymer solution in poor and thin layers acts similar as how it performs in the conventional productive reservoirs. For example, a certain degree of increase in polymer quantity, concentration and molecular weight will produce more oil. Since the different physical properties in the conventional productive reservoirs and the poor and thin layers, polymer solution performs differently in the course of polymer flood. Reservoir permeability, pore throat and its distribution make it more feasible to use medium molecular weight in poor and thin reservoirs, it is hopeful to sweep more pore volume and improve oil recovery. In the poor and thin layers, the medium molecular weight shows an visco-elasticity rhelogical property at the flow velocity of 0.6-6m/d. For the 1000ppm polymer solution, its capillary number is 10-4-10-6, higher...