This paper is an introduction to the sub-surface aspects of the $1 billion Caroline sour gas condensate development. Technical aspects concerning reservoir geology and fluids, well performance and depletion strategy are reviewed.
The Caroline field contains 60 bcm (2.1 tcf) of liquid-rich gas containing 35% H2S. Production is from the high deliverability Swan Hills reservoir at a depth of 3800 m (12400 ft). The nature of the reserves and their proximity to rural population centers impacts the planning process.
The theme of the paper is that hydrocarbon development planning in the 1990's and beyond is constrained due to the legitimate concerns of the local and broader public. In the Caroline example, there was minimal well testing prior to start up as a result of these concerns. Still, a strong consultative effort resulted in an effective use of the data for planning purposes. These efforts determined an appropriate scope for the project which was started up on time and on budget. With limited production data available up front, Caroline is not unlike a major offshore project. The challenge for marketers, builders, operators and sub-surface technical specialists was to provide and execute a development plan and depletion strategy for the project that would meet the needs of both the owners and the affected parties.
The Caroline gas field is located approximately 150 km (90 miles) north of Calgary (Figure 1). Found in 1986, it is the largest discovery of its kind in Western Canada in the last 25 years. Production is from a 60 bcm (2.1 tcf) gas accumulation in the Swan Hills Member of the Devonian Beaverhill Lake Group (Figure 2). Liquid co-production adds considerable value to the sour gas itself.
The project lies in the midst of an extensive rural population base whose needs have been carefully considered in the field development plan. The well testing program was designed with the residents in mind. Of the fifteen wells tied in (Figure 3), only nine were actually flow tested prior to startup of the $1 billion project. Flow rates were severely restricted due to concern over safety, noise, odor, and emissions.
In this context, the following sub-surface aspects of the project are discussed:
* reservoir description and reserves determination for the Swan Hills carbonate bank using extensive seismic data but limitedwell control: