Characterization of Operative Mechanisms in Gravity Drainage Field Projects Through Dimensional Analysis

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Gas-Assisted Gravity Drainage (GAGD) process is being developed through a joint effort between the U.S. DOE and LSU, to examine the effectiveness of improving gravity drainage of oil to horizontal producers by injecting gas through existing vertical wells. To facilitate fair and effective performance comparisons between the conventional wateralternating-gas (WAG) and the GAGD process, and decipher the controlling operational multiphase mechanisms in gas injection EOR processes, the dimensional analysis approach was employed. Nine gravity stable and eight WAG field applications in the U.S., Canada, and rest of the World were studied for this purpose. A newly defined 'index of productivity' and five dimensionless groups, namely Capillary (N C ), Bond (N B ), Dombrowski-Brownell (N DB ), Gravity (N G ), and Grattoni et al.'s 'N' group were calculated for these gravity stable field projects.Dimensional analysis results for all gravity drainage field projects indicated that these dimensionless numbers can be classified into two groups: (i) petrophysical parameter(s) dependent groups: N B , N DB and N, and (ii) operational parameter(s) dependent groups: N C and N G . N C and N B groups effectively envelope the interplay of the dominant reservoir forces, namely gravity, viscous, and capillary forces. These groups coupled with the microscopic Bond number (N DB ) aid in characterizing the flow regimes and governing forces in the field as well as laboratory displacements. The N G and N groups provide useful augmentation for scale-up and displacement characterizations. This paper provides the results of step-by-step dimensional analyses for all the field cases studied and attempts to characterize the controlling multiphase mechanisms in gas injection EOR processes. Additionally, this work attempts to characterize the fluid dynamics associated with gravity drainage processes through existing (namely, capillary number, bond number, gravity number etc.) and newly defined ("gravity drainage" number) dimensionless groups.

Identification of Fluid Dynamics in Forced Gravity Drainage Using Dimensionless Groups

“…This is achieved by reproducing experiments with a relative magnitude of the forces that is the same as those in the field. For this study, we used the values of dimensionless numbers (the capillary and the Bond numbers) in nine gravity stable field projects reported by Kulkarni and Rao (2006) as a basis for our experimental design. In order to capture a larger range of dimensionless groups, the operating parameters were varied extensively.…”

“…For immiscible flow, displacement efficiency could depend on the wetting properties of the fluids, the rate of gas injection and oil production, the difference of oil and gas density, their viscosity ratio, and the oil relative permeability. Investigations in the laboratories and in the field (Hagoort 1980;Chatzis et al 1988;Da Sle and Guo 1990;Bangla et al 1991;Kantzas et al 1998;Rao et al 2004;Kulkarni and Rao 2006;Jadhawar and Sarma 2008) suggest the importance of the gas-oil gravity drainage process in improving the recovery characteristics of gas injection EOR methods. Majority of studies investigate the effect of dimensionless groups on recovery performance (Grattoni et al 2001;Gharbi 2002;Kulkarni and Rao 2006;Wood et al 2008;Jadhawar and Sarma 2008).…”

“…Gharbi (2002) made use of dimensionless groups for scaling of miscible flooding in a 2D heterogeneous anisotropic reservoir. Kulkarni and Rao (2006) presented the effect of important dimensionless groups on the final oil recovery obtained from a number of miscible and immiscible gas gravity drainage experiments. Wood et al (2008) introduced ten dimensionless groups to describe CO 2 flooding in a dipping waterflooded reservoir, and used them for experimental design purposes to develop screening criteria applicable to Gulf Coast reservoirs.…”

Partially miscible VAPEX displacement of a moderately viscous oil

“…It is the ratio of gravitational to viscous forces. It varies in field in the range of 0.1 to about 500 (Kulkarni and Rao, 2006). It is inversely related to the viscous-to-gravity ratio, R v/g discussed by Stalkup (1983).…”

Numerical and analytical study of effects of small scale heterogeneity on CO2/brine multiphase flow system in horizontal corefloods

“…Dimensional analysis has been shown to be very useful to analyze the multiphase flow in porous medium (Kulkarni et al 2006;Wood et al 2008; Kopp et al 2009; Rostami et al 2010). In a recent study (Kuo and Benson 2013), the combined effect of viscous, gravitational, and capillary forces at the core-scale has been studied numerically and analytically for homogeneous cores.…”