The Effect of Fracture Control Sandbody Fracturing Technology After Chemical Flooding

After polymer flooding in Daqing Oilfield, 50% of the remaining oil is still concentrated underground, which is a huge potential for “fourth oil recovery” to increase storage and production. However, it is difficult to exploit and still needs to be tackled. In order to further enhance oil recovery after chemical flooding, a large-scale fracturing enhanced oil recovery technology based on fine reservoir description and accurate residual oil identification is proposed. The effect of large-scale fracturing on enhancing oil recovery is simulated through indoor physical simulation experiments, and verified by field tests. The results show that the residual oil after chemical flooding is mainly distributed at the top of the oil layer and the abrupt part of the oil layer plane, and the main types are two typical features of the plane phase change shielding type and the lateral accumulation interlayer shielding type. Through the physical simulation of fracturing, the recovery rate of the phase-change shielding residual oil after fracturing is 11.5%, and the recovery rate of residual oil after fracturing with side deposition interlayer shielding type increased by 6.4%, and the recovery rate of the shielding residual oil after fracturing is better than that of the phase-change residual oil, confirming the feasibility of this technology. Through field tests, a total of 29 well tests have been carried out. The average daily oil increase of a single well after fracturing is 7.0t at the initial stage, and 2355t after fracturing, increasing the oil recovery by 3.5%. It is expected to achieve the effect of increasing the oil recovery by more than 4.0%. Through the implementation of large-scale fracturing and EOR technology after chemical flooding, the purpose of further economic exploitation of residual oil after chemical flooding has been realized, which has broad application prospects, and can also provide technical reference for the efficient development of other continental sandstone old oil fields.