Abstract

A graphical method is outlined which allows accurate interpretation of the location and rate of growth of a SAGD steam chamber using thermocouple data above the steam chamber. Specific examples from Phase A and Phase B at the Underground Test Facility highlight the power of the new method and demonstrate that steam chamber development is influenced by the presence, shape and orientation of flow barriers, that, in the reservoir discussed, take the form of thin mudstone interbeds. The field data described herein is from the longest-running experimental SAGD pilot, known as the Dover Project or the Underground Test Facility (UTF), which is the incubation site for the SAGD technology and is operated by Northstar Energy.

Introduction

The application of Steam Assisted Gravity Drainage (SAGD) technology to the production of bitumen deposits in northeastern Alberta, Canada, offers the potential to alter the world's oil supply picture. This technology is now moving from the realm of experimental to that of commercial, based on the results of pilot projects. The following presents a method for the analysis of temperature data to further understand the impact of vertical heterogeneity on steam chamber growth.

Bitumen recovery proceeds as the steam chamber slowly rises up due to buoyancy and heats the bitumen around it to the point where the bitumen can drain down the sides of the chamber to a pool at the bottom of the chamber. Due to the fact that the driving force for steam rise is the gravity head, the impact of vertical heterogeneity can be great.

The McMurray formation at the UTF has a high degree of vertical heterogeneity which has a large impact on the ability for steam to rise up through the formation. The availability of cores, dip meters and logs gives a good characterization of the vertical succession, however, the use of thermocouple measurements in the characterization of the reaction of the steam chamber to these heterogenieties has been, to date, only general in nature. This new method allows for the interpretation of steam chamber position to the centimeter scale allowing for the study of steam chamber interaction with individual mudbed occurrences observed in core.

CLASSICAL INTERPRETATION OF TEMPERATURE OBSERVATION WELLS

The classical method for the determination of the top of a SAGD steam chamber is referred to as the inflection method. Within the steam chamber water exists in two phases. Pressure is essentially constant throughout the steam chamber so the temperature within the steam chamber is also constant assuming there is no Non- Condensable Gas (NCG).

Figure 1 shows a typical steam chamber profile. This example comes from Phase A at the UTF previously published by Chalaturnyk1. The presence of the steam chamber is shown by the constant temperature zone from approximately 286 - 274 m above sea level (mASL).

The temperature gradient outside of the steam chamber indicates that heat is being conducted away from the hot steam chamber into the cold reservoir. The sharp inflection between the constant temperature steam zone and the conduction zone shows the top (and bottom) of the steam chamber.

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