Oil Distribution Characteristics for Tight oil Sandstone Cores in the Spontaneous Imbibition plus Waterflooding and Waterflooding-only using Nuclear Magnetic Resonance

Abstract:

During the development of tight reservoirs, the spontaneous imbibition (SI) and displacement always exit simultaneously and closely relate to oil production, it is meaningful to characterize the fluid distribution and flow dynamics during these two processes. In this paper, 6 tight oil sandstone cores from the Ordos Basin in China were performed experimentally to study the fluid flow and oil distributions in the i) SI plus waterflooding, and ii) waterflooding-only using the low-field nuclear magnetic resonance (NMR) technology. The experimental results show that oil was mainly produced from macropores of 20-200μm and micropore of 0-10μm in the SI process, whereas it was only produced from mesopores of 10-20μm in the waterflooding-only. At the same time, the oil produced from the mesopores during the waterflooding after SI processes, and its recovery was higher than the one in the process of waterflooding-only. Moreover, the maximum recovery in the waterflooding after SI process reached 88.43%, which exceeded that of the waterflooding-only process by 18.7%; the average residual-oil saturation from the micropores in the SI plus waterflooding process was 34.18% lower than that of the waterflooding-only process. Overall, the combination of waterflooding with SI avoided the limitations related to waterflooding-only and further improved oil recovery.