Application of a New Crosslinked Polymer Displacement Technology at Bo-19 Block in Gudao Oilfield

A new EOR method of Crosslinked polymer displacement technology is introduced in this paper. The crosslinked system is based on the reaction of Cr(III) in crosslinker with hydrolysed polyacrylamide(HPAM). After gelation, the system has some character such as good viscoelasticity, good thermal stability, and high salinity resistance. The viscoelasticity of crosslinked system can reach 2–3 times simple polymer solution. As a new system combining profile modification and flooding, it can be applied in high water-cut and severe heterogeneous reservoirs. Because of delayed crosslinking property, it can not only improve profile during injection, but also flow increase volumetric sweep efficiency. Having been injected into reservoir, crosslinking polymer can block and adjust high permeability zones in deep section, and improve sweep volume, and decrease water to oil mobility ration, thereby enhance recovery efficiency. The pilot is is in BO-19 block in GUDAO oilfield, which is characteristic of positive rhythm deposit, loosed sand cement, high density and high viscosity etc. The reservoir temperature is 73°C, the viscosity of crude oil is 80mPa.s, density is 0.9030g/cm3 at reservoir conditions, permeability is 1000–2000×10−3μm2 and the formation water salinity is 6453mg/L. It has 21 injection wells and 40 production wells, the oil-bearing area is about 2.4km2 and reserve in place is about 737.3×104 tons. From 1999 to 2001, 0.15PV (pore volumes) of crosslinked polymer solution has been injected, and a good effect of increasing oil and decreasing water appears, oil production increases from 201 to 350 tons per day, composite water cut decreases from 91.3% to 84.6%, cumulative incremental oil reached 5.0×104tons.