JZW oilfield, which was considered as one of the best candidates for polymer flooding with low water salinity and temperature, is one of offshore heavy oilfields in Bohai bay. Based on a lot of the laboratory and numerical simulation studies, the polymer flooding test was initialed in 2007 while the area comprehensive water cut was 80%. By 2008, all injection wells in the area were transferred to polymer injection wells. For the effect of polymer flooding test, lots of measure adjustment was taken to optimize the injection and production structure, control the produced polymer concentration.

At present, the obvious response to increasing oil and decreasing water cut is seen in the test area, 0.18PV polymer solution has been injected in the area, and the response was seen in almost all 21 producers. The average daily oil production rate of 10 typical producers increased from 190 bbl to 310 bbl, and the average water cut decreases from 85.2% to 63.1%. It can be observed from the production history of the target block of the similar rule as the typical well which the water cut increased after polymer flooding and reached the maximum value of 80%. With the polymer injected, the water cut decreased by a maximum of about 10% to 70% while oil production rate increased by about 30%.

Now, the performance of the oilfield is basically in agreement with the results predicted by numerical simulation, expecting that the polymer flooding oil recover can be 6.2%(OOIP) higher than the water flooding. For the higher recovery, the surfactant-polymer flooding test has been run in one of the well groups of the area since last year.

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