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Optimization of Operating Design and Production Strategies in Discontinuous SAGD Technique

The SAGD process is an effective method for heavy oil and bitumen production. Recently, some innovative techniques based on SAGD process have been proposed by several authors such as continuous SAGD, Fast-SAGD, Hybrid SAGD, FA-SAGD. However, their economic efficiency are still questionable in that those process are only interested in technical issues without estimating the economic effectiveness associated with high capital investment and operating costs, and uncertainties of oil and gas prices in the market.

Main problem is that how we can design optimum operating conditions to inject a reasonable amount of steam with specific injection pressure under reservoir condition in order to maximize economic feasibility. The previous studies conducted sensitivity analysis and optimization of SAGD performance by classical methods based on their numerical simulations. Therefore, there was a lack of confidence level because they didn’t determine the significance level of parameters and ignored interactions effects between considered parameters, which may lead to low efficiency issues in a field operation. These restrictions can be overcome by applying D-optimal design and response surface methodology to find the best design of operating conditions for the prediction of SAGD performance. By using this methodology, discontinuous SAGD technique was operated to control the amount of steam injected and improve oil recovery at several time intervals.

The NPV was used as measurement unit to control the steam injection efficiency as well as the operational effectiveness among thermal recovery methods based on fluctuations of oil and gas prices. Total 28 cases was run to optimize the parameters of operating conditions and the NPV responses during 10 years. The most suitable design of operating conditions in Peace River reservoir are vertical spacing between well pairs of 12m, injection pressure of 3400kPa, steam injection rate of 500m3/d, subcool of 50oC, and well pattern spacing of 74m. In case of optimal time interval of steam injection, the maximum NPV was obtained when steam rate can be injected to the reservoir continuously during 180 days, then the steam injection stopped for next 90 days. The discontinuous SAGD performance showed that the amount of steam injected and water production reduced significantly. Moreover, heat losses were minimized and oil recovery was increased, which led to the NPV higher than other thermal recovery methods.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California