Q. Doan

Experimental Modelling of the SAGD Process 3/4 Enhancing SAGD Performance with Periodic Stimulation of the Horizontal Producer

Experiments on initial stages of the steam-assisted gravity drainage (SAGD) process were carried out, using 2-D scaled reservoir models, to investigate production process and performance. Expansion of the initial steam chamber, its shape and area, and temperature distributions were visualized using video and thermal-video pictures. The relationship between isotherms and steam chamber interface was investigated to study the drainage mechanism. The temperature at the interface where the steam chamber was expanding was observed to remain nearly constant at 80°C. Effect of vertical spacing between the two horizontal wells on oil recovery was also investigated. For the case of conventional SAGD, oil production rate increased with increasing vertical spacing; however, the lead time for the gravity drainage to initiate oil production became longer. The results suggest that L can be used as a governing factor to evaluate production rate and lead time in the initial stage of the SAGD process. Based on these experimental results, the SAGD process was modified: the lower production well was intermittently stimulated by steam injection, in conjunction with continuous steam injection in the upper horizontal injector. Using the modified process (named SAGD-ISSLW), the time to generate near breakthrough condition between two wells was shortened, and oil production was enhanced at the rising chamber stage compared with that of the conventional SAGD process.

Simulation of Sand Transport in a Horizontal Well

An important application of horizontal well technology in Canada is recovering oil from marginal heavy oil reservoirs in Saskatchewan and Alberta. These reservoirs are often poorly consolidated ; as a result, recovery operations are susceptible to sand production which potentially poses a serious problem as the sand particles deposit and partially block the horizontal well. This work presents a mathematical treatment of the transport process of oil and sand particles inside a horizontal well. In particular, the model described in this paper formulates the transport process mechanistically. Equations of mass and momentum conservation for the solid phase (sand particles) and the fluid phase (oil) are formulated. The oil is assumed to be Newtonian, and the sand particles are assumed to be spherical in shape and uniform in size. In addition, the model incorporates empirical correlations to describe the interaction between the two phases. The system of equations is solved numerically to determine the distribution of sand particles and oil, their pressure and velocity distributions as a result of the presence of a constriction inside the horizontal well. Simulation results obtained provide insight into the mechanisms involved in the transport process, thus enhance the understanding of the flow of sand and oil inside a horizontal well. This, in tum, yields some guidelines for production operations involving horizontal wells in unconsolidated and poorly consolidated reservoirs.

Sand Transport in a Horizontal Well: A Numerical Study

Horizontal wells have been shown to be successful in improving oil recovery for marginal heavy oil reservoirs in Saskatchewan and Alberta. One commonly encountered problem in recovery operations for these unconsolidated reservoirs is the production of sand and fines. The settling and accumulation of the solid particles inside the horizontal wellbore represents a serious problem, with the horizontal well becoming partially plugged being a real possibility. This study investigates this problem, with focus on determining the roles played by different flow parameters on the settling and transport process. The physical model described in this work examines the transport process mechanistically. Conservation equations for the solid phase (sand particles) and the fluid phase (oil) are formulated, with the interaction between the phases described by empirical correlations. The oil is assumed to be a Newtonian fluid, and the sand particles are assumed to be spherical in shape and uniform in size. The system of equations is solved numerically to determine the distribution of sand particles and oil, and the respective pressure and velocity distributions as a result of the presence of a constriction inside the horizontal well. According to the simulation results, oil viscosity and particle size play important roles in the transport process, including controlling the gravitational settling tendency of solid particles inside the horizontal wellbore. The results provide insight into the mechanisms involved in the transport process; as such, they provide guidelines for production operations involving horizontal wells in unconsolidated and poorly consolidated reservoirs.