A Numerical Model for Investigating the Steam Conformance along the Dual-String Horizontal Wells in SAGD Operations

Abstract

Non-uniformity of the steam-assisted gravity drainage (SAGD) steam chamber significantly decreases the development of heavy oil reservoirs. In this study, to investigate the steam conformance in SAGD operations, a wellbore model is developed for fluid flow in dual-string horizontal wells. Then, a three-dimensional, three-phase reservoir model is presented. Next, the coupled wellbore and reservoir model is solved with a fully implicit finite difference method. Finally, the effects of the injector wellbore configuration, steam injection ratio and injection time on the steam conformance are investigated. The results indicate that under different injector wellbore configurations, the closer the differences between the pressure drop from the landing position of the short string to the heel of the wellbore and the pressure drop from the landing position of the short string to the toe of the wellbore, the better is the steam conformance. The smaller the difference in the steam injection rate between the long and short injection strings, the higher is the uniformity of the steam chamber. The injector annular pressure profile uniformity is consistent with the steam conformance. Creating a more uniform steam pressure in the annulus of the injector improves the uniformity of the steam chamber. The steam conformance decreases with increasing injection time, so the optimization method of steam chamber uniformity should be adjusted according to different injection times.

Influence of Vertical Downward Annulus Eccentricity on Steam-Water Two-Phase Flow Pressure Drop

“…In the above equations, λ is the friction resistance coefficient, dimensionless; L LS is the liquid slug length, in meters; and L SU is the length of slug unit, in meters [16]. e presentation form of two-phase mixture parameters is shown in (8), where ρ m is the density of two-phase mixture, in kg•m −3 ; α is the sectional void fraction, dimensionless; μ m is the viscosity of two-phase mixture, in Pa•s; v m is the velocity of two-phase mixture, in m•s −1 ; h m is the enthalpy value of two-phase mixture, in kJ•kg −1 ; μ g is the viscosity coefficient of gas phase, in Pa•s; μ l is the viscosity coefficient of liquid phase, in Pa•s; h l is the enthalpy value of liquid phase, in kJ•kg −1 ; and h g is the enthalpy value of gas phase, in kJ•kg −1 . (b) e annular flow is as follows:…”

“…Caetano pointed out that solving the plane angle in eccentric annulus is different from that in concentric annulus. See the calculation of plane angle in (8), where e is the eccentricity, dimensionless; K is the radius ratio of annulus tube, dimensionless, K � D T / D C ; and W T ′ is the plane angle toward the tubing wall, in rad. e symbol denotes the mean values along the annular cross section.…”

“…e symbol denotes the mean values along the annular cross section. Since (8) has no analytical solution, the approximate solution can only be obtained by using numerical algorithm such as the complexification Simpson rule.…”

“…Dong et al [7] developed a model for the flowing and heat transfer of multicomponent hot fluids (including superheated water vapor, nitrogen, and carbon dioxide) in the concentric dual-tubing wellbore and parallel dual-tubing wellbore, taking the impact of wellbore temperature and pressure on its thermophysical properties into consideration. Li et al [8] explored the influential law of steam injection well structure, steam injection proportion, and steam injection time on the physical properties of steam in the SAGD dual-tubing horizontal wellbore. On the basis of the flowing and heat transfer model of concentric dual-tubing wellbore, Han et al [9] considered the phase state variation of CO 2 and explored the pressure and temperature distribution of CO 2 in concentric casing.…”

Simulation and Production Optimization on Enhanced Oil Recovery during the Middle and Late Period for SAGD Development in Ultraheavy Oil Reservoirs with Interlayers

“…In addition, the introduction of vertical wells to optimize SAGD has mainly included the following combinations: a single vertical and a single horizontal well, vertical wells assisted by double horizontal wells, and a single horizontal well and multivertical wells [32,33]. For the improved SAGD technique using the combination of a single vertical and a single horizontal well, scholars have established a productivity prediction model.…”