Will Using LSASF Affect the Rock Properties of Sandstone and Increase Oil Recovery?
- Al-Saedi N. Hasan (Missouri University of Science and Technology / Missan Oil Company) | Flori E. Ralph (Missouri University of Science and Technology) | A. K. Qasim (Petroleum research and development center / Iraqi Ministry of Oil)
- Document ID
- American Rock Mechanics Association
- 53rd U.S. Rock Mechanics/Geomechanics Symposium, 23-26 June, New York City, New York
- Publication Date
- Document Type
- Conference Paper
- 2019. American Rock Mechanics Association
- 1 in the last 30 days
- 26 since 2007
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ABSTRACT: Emerging techniques to enhance oil recovery combine injection of low salinity (LS) water with steam - the so-called LSASF. In this study, we investigate the effect of LSASF on rock properties for the Bartlesville Sandstone Reservoir. Three sandstone cores were prepared and tested as follows: reservoir core#12 (RC12) was flooded with. formation water (FW) and steam, RC13 was flooded with seawater (SW) and steam, and RC14 was flooded with LS water and steam. The permeability was measured before and after core flooding. A reactive transport modeling was performed to measure the effect of flooding the cores on permeability and porosity. Contact angle measurements were also conducted to assess the LSASF on the cores’ wettability. The core-flooding experiments showed that the highest oil recovery could be obtained by flooding RC14 with LS water and steam, which was 64.7% of the OOIP, while it was 54.23% and 51.4% of the OOIP for both RC13 and RC12, respectively. The permeability measurements showed that the permeability decreased after flooding the cores with all the brines and the largest reduction was with the highest salinity. The reactive transport modeling agrees with the measurements.
The temperature of heavy oil reservoirs is usually low. These reservoirs are located at shallow depths. Low temperature makes the oil heavy, and shallow depth means there is not enough energy to lift the oil to the surface. As a result, low temperature and low depth are both challenges when extracting heavy oil from these reservoirs. In order to extract the heavy oil, thermal enhanced oil recovery (EOR) techniques must be applied. Thermal EOR techniques applied heat to the heavy oil to reduce its viscosity and ease flowing of oil to the surface. Many steam projects have been conducted in heavy oil reservoirs, and the results of oil recovery were significant (William et al., 1961; Ali, 1974; Reis, 1990; Reis and Miller, 1991; Alikhlalov and Dindoruk, 2011; Alvarez and Han, 2013; Bera and Babadagli, 2015), but injecting steam itself is not always the right decision. Due to the density difference between the injected steam and the in-situ heavy oil, the mobility ratio is weak and substantial heavy oil quantities are left behind. In order to overcome the density differences between the injected steam and the in-situ heavy oil, water alternating steam process (WASP) has been proposed (Hong and Stevens, 1990; Hong and Stevens, 1992; Bautista and Friedmann, 1994; Am et al., 2014; Ariza et al., 2016). Slugs of water are injected behind the steam to improve its sweep efficiency. The idea of WASP is similar to that in water alternating gas flooding (WAG). Generally, the water used in WASP is any water available to the project location such as formation water (FW), or seawater (SW) regardless of the salinity of the water. Conducting WASP projects provides additional oil recovery than steam does. Later, Al-Saedi and Flori et al. (2018d) proposed a new technique to replace the regular water used in WASP by low salinity (LS) water and named it low salinity alternating steam flooding (LSASF). The new idea has developed from the use of water flooding in improved oil recovery. Injecting regular water with high salinity does increase oil recovery by improving the displacement efficiency but reducing the same regular water salinity is more beneficial in improving the oil recovery (Ali, 1974; Sufi, 1990). Decreasing water salinity has been proven to provide more oil recovery because the LS water can alter the rock wettability towards being more water-wet (Lager et al., 2006; Austad, 2013; Nasralla and Nasr El-Din, 2014, Al-Saedi et al., 2019a). Increasing rock water-wetness is a favorable condition to release the oil from the rock. The mechanisms of LS water flooding are: fines mobilization (Tang and Morrow, 1999), reduction in interfacial tension and increased pH (McGuire et al., 2005), multicomponent ion exchange (Lager et al., 2008), double-layer expansion (Ligthelm et al., 2009), organic material desorption from the clay surface (Austad et al., 2010), mineral dissolution (Pu et al., 2010), cation exchange on quartz surface (Al-Saedi and Brady et al., 2018), and organic material desorption from quartz surface (Al-Saedi and Brady et al., 2018). Therefore, replacing regular water used in WASP with LS water has two advantages: (1) Improves the steam sweep efficiency (as regular water does in WASP), and (2) Triggers the rock wettability to be altered towards being more water-wet.
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