Heat Transfer Ahead of a SAGD Steam Chamber, a Study of Thermocouple Data From Phase B of the Underground Test Facility (Dover Project)

Abstract

Abstract Phase B at the Underground Test Facility (Dover Project) is the longest running and most instrumented SAGD pattern in the world and is operated by Northstar Energy. Techniques are presented which allow for the interpretation of temperature data from the pilot to better understand the growth of a SAGD steam chamber over time. Calculating the rate and direction of steam chamber movement, the in situ thermal diffusivity and the role of conduction and convection in heat transfer provide a foundation for understanding the interaction between the SAGD recovery process and the reservoir. Introduction Over twelve years have passed since the first field test of the classical SAGD recovery process at the Underground Test Facility (UTF) near Fort McMurray, Alberta, Canada. In recent years the level of activity in thermal heavy oil has increased dramatically in Canada. Butler has identified four commercial SAGD projects currently under construction or where construction is to commence soon and two additional announced projects all of which could total over one half million barrels per day of production by 20101. One of the most striking characteristics of the SAGD technology is that it has undergone relatively little change since its first field trial. Fundamentally, the commercial projects which are currently under construction look very much like the original 50m Phase A horizontals, placed on production in 1988. One reason for little change in the SAGD technology is that, so far, it has delivered excellent results. The early piloting of the SAGD process at the UTF has proven that the SAGD process can deliver good rates and reserves from the reservoir at the UTF, which is considered to be inferior to 1/3 of the Athabasca resource2. In spite of this perception that the UTF reservoir is marginal, the first commercial length wellpairs at Phase B were highly successful reaching a normalized productivity of 0.2 m3/d per meter of well length3. In addition to the success of the SAGD process in recovering oil, SAGD also benefits from the fact that the performance of the early pilots was highly predictable. Butler's equation4, developed without the benefit of any field data, has been shown to accurately predict the performance of SAGD in the field. The high predictability of the process has meant that the results of early pilots, especially the UTF pilot, have been used to history match simulation models, which have been, in turn, used to predict the performance of SAGD in new reservoirs. In fact, the subject of much of the literature on SAGD is the results of simulation modeling.5,6,7 At times the results of simulation modeling are used as a basis for scientific conclusion, typically reserved for real field evidence. Relatively little actual field data is available in the public domain, which exacerbates the situation. Typically, when a new reservoir process is developed and tested in the field, a great effort is required in studying the underlying physics of the process in light of the field data, prior to simulating the process. The nature of the SAGD process, as evidenced by the results of the early pilots, has allowed this step to be essentially skipped, at least until now. As SAGD is applied to more locations within the Oil Sands of the Western Canadian Sedimentary Basin, our ability to predict its behavior seems to be degraded. Although, the reservoir at the UTF has been referred to as marginal (primarily due to the fact that it is only 20m thick), it does have one striking feature. The McMurray succession at the UTF is a sand dominant succession with relatively little mudstone. Moving south from the Fort McMurray region, the McMurray formation tends to become less sand dominant with the volume of mudstone generally increasing with a corresponding increase in vertical heterogeneities.