Numerical Simulation Of The Steam-Assisted Gravity Drainage Process (SAGD)
Authors: Chow L. , Butler R.M. 
Published: March 2010

Physical and numerical models can be employed together to better understand the SAGD process. When there are inadequate measured physical properties as input data, and insufficient built-in mathematical processes, it is beneficial to validate a numerical model by history matching physical model results.

Based on Chung's experimental data from a physicalmodel, a two-dimensional, three-phase (bitumen, water and steam) and two-component (water & bitumen) black oil numerical model for the SAGD process was developed and tested, using the CMG "STARS" thermal simulator. Both the "Spreading Steam Chamber" and the "Rising Steam Chamber" processes were simulated. The numerical results agree reasonably well with the measured data for cumulative oil production, recovery percentage and temperature profiles in the model at different times.

The results from the numerical simulation were found to be relatively insensitive to the form of the relative permeability functions employed. Linear relative permeability curves were employed to simulate the experimental production results. The model can be employed as a tool to aid in sensitivity studies and in the interpretation of the laboratory results.

Introduction

A reservoir can only be produced once, and it is often difficult and costly to correct mistakes in the approach, once the project has been initiated. However, a model study can be conducted several times and alternatives examined. Therefore, before launching any new technology, it is advisable to conduct extensive testing, using physical and numerical models, to evaluate various scenarios for the optimization of pattern type, size, well completions and rates. It is important, technically and financially, to have a prediction of the performance that is likely to be achieved from a given proposed recovery scheme for a given reservoir.

Models, both physical and numerical, improve the understanding of reservoir processes. A physical model can provide a means for checking the accuracy and assumptions of the numerical model. Validating the numerical model is advisable by history matching with a well-defined physical model to overcome some of the limitations of numerical modelling.

In some recovery processes, such as the Steam-assisted Gravity Drainage (SAGD) process(l), the physics of the situation is so complex that both physical and numerical models should be employed as complementary tools to obtain insight into different mechanisms and determine which strategies will optimize the process. Several field pilots using the SAGD process are underway. These include the three Esso Resources horizontal pilot projects at Cold Lake, Alberta, the Sceptre Resources pilot project in the Tangleflags North field near Lloydminster, Saskatchewan, and the Alberta Oil Sands Technology and Research Authority's (AOSTRA) Underground Test Facility (UTF) project in the Athabasca field near Fort McMurray, Alberta.

Scope and Objective of Study

The scope of this numerical simulation study is to match the oil recovery and the steam temperature interface position as observed in Chung's physical model(2,6) of the SAGD process. The objective is to investigate the feasibility, using a commercial CMG simulator ("STARS"), to history match the SAGD process, particularly the "spreading steam chamber" phase and the "rising steam chamber" phase.