Field test on air-assisted steam flooding of heavy oil field

Field test and research was carried out on air-assisted steam flooding of heavy oil field to investigate its production effects. Five well groups whose development mode was in urgent need to be transformed due to the depleting crude oil and the serious steam channeling and overlapping in oil reservoirs were selected from the steam flooding test area of Qi 40 Block. And then field test was carried out on these five well groups. It is shown that the average daily oil production per well group of 5 test well groups is increased from 14.8 t/d to 16.1 t/d and the oil/steam ratio is increased from 0.14 to 0.17. The vertical producing degree of oil layers is increased significantly. It is indicated from the analysis that the injected air firstly sweeps in the predominant direction of steam flooding vertically and areally and low-temperature oxidation reaction happens between the injected air and the residual crude oil, increasing the bituminous sediments in pores. And consequently, the permeability of oil layers is decreased to force the steam to divert, so that the sweeping area of steam is enlarged. It is revealed that continuous air/steam injection is the suitable mode for air-assisted steam flooding; the recovery factor is higher when the steam/air ratio is close to 1:40; and if the well spacing is 70 m, the reservoir temperature will rise slightly and the content of produced oxygen can drop to the safety range after low-temperature oxidation reaction happens between the underground crude oil and the injected air. The success of field test demonstrates the feasibility of air-assisted steam flooding to improve the production of heavy oil fields. The problems of the selected test well groups are common in the late production stage of well groups in ordinary heavy oil reservoirs developed by steam flooding, so the test method and the related technical parameters in this paper can be used as the reference for the air-assisted steam flooding of similar well groups.