Nuclear Magnetic Resonance Measurement of Oil and Water Distributions in Spontaneous Imbibition Process in Tight Oil Reservoirs

Abstract

Spontaneous imbibition of water into tight oil reservoirs is considered an effective way to improve tight oil recovery. We have combined testing techniques such as nuclear magnetic resonance, mercury injection capillary pressure, and magnetic resonance imaging to reveal the distribution characteristics of oil and water during the spontaneous imbibition process of tight sandstone reservoir. The experimental results were used to describe the dynamic process of oil–water distribution at the microscopic scale. The water phase is absorbed into the core sample by micropores and mesopores under capillary forces that dry away the original oil phase into the hydraulically connected macropores. The oil phase entering the macropores will drive away the oil in place and expel the original oil from the macropores. The results of magnetic resonance imaging clearly show that the remaining oil accumulates in the central region of the core because a large amount of water is absorbed in the late stage of spontaneous imbibition, and the water in the pores gradually connects to form a “water shield” that blocks the flow of the oil phase. We propose the spontaneous imbibition pathway, which can effectively explain the internal mechanisms controlling the spontaneous imbibition rate. The surface of the core tends to form many spontaneous imbibition pathways, so the rate of spontaneous imbibition is fast. The deep core does not easily form many spontaneous imbibition pathways, so the rate of spontaneous imbibition is slow. This paper reveals the pore characteristics and distribution of oil and water during the spontaneous imbibition process, which is of significance for the efficient development of tight oil.

Fast Advective Water Flow Through Nanochannels in Clay Interlayers: Implications for Moisture Transport in Soils and Unconventional Oil/Gas Production

“…For example, because of its high velocity, interlayer flow could play a critical role in moisture transport in soils and water uptake by plants, especially in a semiarid or arid region, where a large fraction of water is expected to be retained in clay interlayers. In addition, the molecular-level understanding of water transport in nanometer or sub-nanometer hydrophilic channels obtained in this work may also shed light on issues related to water imbibition or its release during unconventional oil/gas production . The classical Washburn equation suggests that the imbibition of liquid in horizontal channels is a diffusive process .…”

“…In addition, the molecular-level understanding of water transport in nanometer or sub-nanometer hydrophilic channels obtained in this work may also shed light on issues related to water imbibition or its release during unconventional oil/gas production. 52 The classical Washburn equation suggests that the imbibition of liquid in horizontal channels is a diffusive process. 53 Owing to a possible occurrence of clay interlayer flow, the rate of water imbibition or its release could be much faster than that predicted from classical approaches.…”

Effect of pH on the Dominant Mechanisms of Oil Recovery by Low Salinity Water in Fractured Carbonates

“…The complex pore structure of the core and oil−water distribution make it difficult to form a long-path SIP, which can lead to a decrease in the rate of SI. 62 The different regions of the SI are illustrated in Figure 10.…”

Experimental Study on Enhanced Shale Oil Recovery and Remaining Oil Distribution by CO2 Flooding with Nuclear Magnetic Resonance Technology

“…This is consistent with the description of the T 2 spectral distribution. According to the methods of Lai et al and Nie and Chen and Zhu et al, , in this study, the shale pores are divided into three types, as shown in Table , and pore volumes at different scales, as shown in Table . The volume ratios of the micropores, mesopores, and macropores are 59.05, 31.64, and 9.31%, respectively.…”