Experimental investigation on the impact of connate water salinity on dispersion coefficient in consolidated rocks cores during Enhanced Gas Recovery by CO2 injection

Abstract

Connate water salinity is a vital property of the reservoir and its influence on the displacement efficiency cannot be overemphasised. Despite the numerous analytical literatures on the dispersion behaviour of CO 2 in CH 4 at different parametric conditions, studies have so far been limited to systematic effects of the process while parameters such as connate water salinity of the reservoir has not been given much attention and this could redefine the CO 2 -CH 4 interactions in the reservoir. This study aims to experimentally determine the effect of connate water salinity on the dispersion coefficient in consolidated porous media under reservoir conditions. A laboratory core flooding experiment depicting the detailed process of the CO 2 -CH 4 displacement using Grey Berea sandstone core sample at a temperature of 50 o C and at a pressure of 1300 psig was carried out to determine the optimum injection rate, from 0.2-0.5 ml/min, for the experimentation based on dispersion coefficients and methane recovery in the horizontal orientation. This was established to be 0.3 ml/min. At the same conditions, the effects of connate water saturation of 10% and a salinity of 0 (distilled water), 5, and 10% wt. with a CO 2 injection rate of 0.3 ml/min on the dispersion coefficients was investigated. The results from the core flooding process indicated that the dispersion coefficient decreases with increasing salinity, hence the higher the density of the immobile phase (connate water) the lower the dispersion of CO 2 into CH 4 . This is a significant finding given that the inclusion of the connate water and its salinity have an effect on the mixing of the gases in the core sample and should be given importance and included during simulation studies for field scale applications of Enhanced Gas Recovery (EGR). This is the first experimental investigation into the relationship between the connate water salinity and the dispersion coefficient in consolidated porous media.

Influence of Permeability and Injection Orientation Variations on Dispersion Coefficient during Enhanced Gas Recovery by CO2 Injection

“…The interstitial velocities were varied according to individual core samples given their different porosities. A range of interstitial velocities was based on the injection rates in our previous work [8], which were evaluated using Equation 7:…”

“…The Helium Porosimeter PORG 200™ (Corelab, OK, USA and Gas Permeater PERG 200 ™ (Corelab, OK, USA) were used to measure the porosity and permeability of the core samples respectively. Details of the equipment description, principles of operation, and procedure can be found in our previous works [8]. The results are shown in Table 2.…”

“…In our previous works [6][7][8][9], we studied some of the factors that affect in situ mixing between the injected CO 2 and the displaced CH 4 which have not been previously considered. These factors include the connate water salinity, the injection orientation and, also, the flow behaviour of CO 2 in its supercritical state during EGR displacement.…”

A Review of Gas Injection in Shale Reservoirs: Enhanced Oil/Gas Recovery Approaches and Greenhouse Gas Control

“…The injected CO 2 contributes to releasing and displacing methane from the micropore walls of organic shales, making the EGR possible. However, the salinity of connate water could reduce the EGR performance by decreasing the dispersion coefficient of CO 2 into CH 4 [92]. In addition, the intrinsic heterogeneity of shale rock generally negatively affects gas production in primary depletion [93,94]; however, it is expected to play a positive role in huff-n-puff gas injection EGR, similar to oil shale EOR [5,7,16,37,94].…”

Enhanced gas recovery by CO2 injection: Influence of monovalent and divalent brines and their concentrations on CO2 dispersion in porous media

“…Some of the investigated factors/parameters include the effects of injected CO2 purity on the displacement process during EGR (Nogueira and Mamora, 2005;A. T. Turta et al, 2007), reservoir heterogeneity (Honari et al, 2015;S Sim et al, 2009), injection orientation and petrophysical properties variation (Abba et al, 2018a;Abba et al, 2019b;Liu et al, 2015Liu et al, , 2018Sim Sim et al, 2009;Zhang et al, 2014), injection rates (Hughes et al, 2012), temperature and pressure (Liu et al, 2020), relative permeability and sweep efficiency (Al-Abri et al, 2012), connate water presence and salinity (Abba et al, 2018b;Honari et al, 2016). Understanding these parameters as they relate to the insitu mixing between the gases and their interaction with the porous media is vital to a successful implementation and adoption of any CO2-EGR process.…”