Abstract

The cyclic steam stimulation is an important thermal recovery technique which is used to develop heavy oil reservoirs. However, the development effectiveness is limited in steam huff-puff wells of heavy oil reservoir with edge water because of the sharply increased water cut caused by the incursion of edge water. An experimental device, which can simulate edge water and steam stimulation process, was designed on the basis of steam flooding device to investigate the nitrogen foam anti-edge water-incursion technique. The designed device includes 3 subsystems: reservoir physical simulation subsystem, edge-water simulation subsystem and fluid injection subsystem. The effect factors and application conditions of the technique were investigated, and the results showed that the effect of the technique was influenced by reservoir water-flooded degree, edge water energy and crude oil property significantly. This technique is more suitable for seriously water-flooded reservoirs whose cycle water cut is no less than 80%, and the reservoir edge water energy and heavy oil viscosity should be moderate. As for Henan heavy oil reservoir, the optimum edge water pressure is 4MPa, and the oil viscosity is less than 5000mPa·s at the reservoir temperature (stock tank oil). The optimum injection pattern of the technique is N2 slug – nitrogen foam slug – steam. Pilot tests were conducted based on experimental results. The operation success rate is 100%, the average cycle water cut is reduced by 23%, and the average cycle oil production is increased twice. In view of the test result, this technique is a successful measurement to inhibit the water incursion and enhance the oil recovery of steam huff-puff wells with edge water.

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