Abstract

Shengli oilfield, the third largest oilfield in China, has abundant ordinary heavy oil resource and steam flooding is one of the most common used recovery methods for it. However, several obstacles have been encountered by conventional steam flooding in those blocks: (1) The significant heterogeneity of formation makes severe steam override and steam channeling. (2) The deposition of reservoir is deep, leading to severe heat-loss. (3) The distribution of remaining oil after water flooding is dispersing.

Laboratory experiments, numerical simulations and field performances of the displacing agent/foam assisted steam flooding pilot are described in this paper. It is an enhanced oil recovery process uses an injectant containing steam and additives consist of oil displacing agent, foam agent and nitrogen gas.

Laboratory experiments indicate that oil recovery factor for displacing agent/foam assisted steam flooding in porous media is much larger than that of steam flooding. Numerical simulation results present that the enriched remaining oil in lower layers caused by steam overlay is effectively produced by using the additives compared with using steam individually.

Displacing agent/foam assisted steam flooding conducted in two well groups at Gudao block is the first field test in Shengli oilfied. The smaller well group consists of one injection well and nine production wells, while the bigger group consists of four injection wells and twenty-one production wells. The total water cut for the smaller well group has decreased from 83.8% to the lowest of 79.4% and daily oil production has been improved from 49.0t to 62.4t. The total water cut for the bigger well group has decreased from 91.0% to 85.7% and daily oil production has been increased from 70.1t to 113.0t. Therefore, displacing agent/foam assisted steam flooding is expected to be a more efficient method than conventional steam flooding to improve oil recovery in Shengli oilfield.

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