Improving the Performance of SAGD

In the recent years several SAGD projects have been initiated for the recovery of heavy oil and bitumen. Every operator is coming across new learning almost every day, although most of this information is proprietary. This paper presents a general discussion, supported by simulation and analytical results, on the different aspects of improving the performance of SAGD operations. The first component is the well bore design, which has to match with the gravity drainage rate. Operating pressure plays a significant role in the rate of recovery. Lower operating pressure reduces the SOR, lower H2S production, may reduce the silica dissolution, thereby, reduce the water treatment issues. However, low pressure operation increases the challenges of lifting the fluid to the surface. Steam additives may be the other option to increase the energy efficiency of the process. Introduction The enormous potential of the Athabasca oil sand dwarfs the resources of many oil producing nations throughout the world. The growth plan for the development of these resources runs into hundreds of billions of dollars in investment. Figure 1 presents the forecast for the growth of the western Canadian oil sand production in relation to production from other resources. More than 50% of the oil sand production is planned to be extracted by in situ recovery processes. A list of the announced projects for the near future development is presented in Table 1. Except for a few projects that involves extraction of the near surface resources through mining, about 2.6 million bpd out of the total 3.5 million bpd is planned to be recovered through SAGD (Steam Assisted Gravity Drainage) process. Figure 1 Western Canadian Petroleum Production outlook SAGD in Athabsca reservoir is different from application of this process in heavy oil reservoirs or equivalent API reservoirs in a different geological setting. Most part of the Athabasca reservoir is thicker than 15 m (close to SAGD economic cut off), shallow (suitable for steam injection) and fairly homogeneous without significant barrier for the growth of the steam chamber. The bitumen is virtually immobile at the reservoir condition with very little initial gas saturation. Compared to these, the Venezuelan resources with equivalent API are present in a deeper formation at higher temperatures and have higher initial GOR and significantly lower in situ viscosity. This is very similar to the conditions of a conventional heavy oil reservoir. Therefore, SAGD may not appear as effective compared to other recovery processes. However, for the Athabasca resources at the current state of recovery technologies, SAGD remains the primary recovery mechanism and is the most effective solution. Currently there are three large (>25,000 bpd) commercial and over eight pilots /small commercial projects are in operation. Two large commercial projects are being built and scheduled to commence operation in 2006. Altogether there is collective knowledge of operation for over 20 years (the first pilot started in eighties). As the enormous volume of operational data pours in the operators are enriching their learning almost every day. This learning pertains not only to the SAGD reservoir technology and it encompasses the whole spectrum of the well bore hydraulics and most prominently the technologies in the operation of surface facilities. The most important of all is the practical aspects of the water treatment technology, which is the heart of any SAGD operation. All of these technologies are being refined continuously for the 0 100 200 300 400 500 600 70