Influence factors and effect prediction model of the tertiary migrations of remaining oil

Abstract

Worldwide, for older fields that are in the late stages of production period, production wells that lose production value due to high water cut are usually shut down. In this situation, the remaining oil in the reservoir will be re-enriched under the influence of gravity differentiation and capillary forces. Production practices find when the production well is closed for a long time and then opened for restarting production, the water cut drops dramatically and the output rise sharply. In order to anticipate the effects of enrichment of remaining oil in the reservoir, this paper analyzes 10 influencing factors respectively. Secondly, change of water cut before and after shut-in is used as the evaluation index of residual oil enrichment effect. Numerical simulation method is used to simulate the influence of different factors on the effect of external migrations of remaining oil at different levels. Grey correlation analysis is utilized to rank the correlation of 10 factors on residual oil enrichment and then we can get the main controlling factors affecting residual oil enrichment. Finally, the response surface analysis method is used to establish a 5-factor 3-level model, and the corresponding prediction results are obtained through numerical simulation experiments. The main control factors are fitted to obtain the prediction formula of the remaining oil enrichment effect. As a result, we can use the prediction formula to forecast the enrichment effect of remaining oil under different reservoir parameters.

Simulation analysis of the mechanism and influencing factors of remaining oil secondary enrichment in ultra-high water cut fault block reservoirs

“…The experimental results show that changing the injection direction can effectively displace the remaining oil in the enriched area. Zhang et al (2021) took the change in water cut before and after well shut-in as the evaluation standard of the remaining oil enrichment effect, obtained the main controlling factors by using a numerical simulation method, and proposed the prediction formula of the remaining oil enrichment effect. Fan et al (2021) discussed the displacement mechanism of the remaining oil film in the microchannel through numerical simulation and proposed that increasing the horizontal stress on the oil film can fundamentally mobilise the oil film and make it movable.…”

Investigation of the Flow Intensity in an Inverted Seven-Point Well Pattern and Its Influence on the EOR Efficiency of S/P Flooding

“…Meanwhile, the intensity affects the occurrence of remaining oil [30,31]. The classification mechanism of remaining oil mainly includes the shape factor method [32,33] and the mechanical method [34,35]. According to the shape of the remaining oil and its contact relationship with the pores, the remaining oil types can be divided into cluster, slit, film, intergranular and corner [36].…”