Optimization of a Vertical-Horizontal Heavy Oil Thermal Operation by using Automated Field-scale Control
- Yu Bao (University of Calgary) | Jing Yi Jacky Wang (University of Calgary) | Ian Donald Gates (University of Calgary)
- Document ID
- Society of Petroleum Engineers
- SPE Heavy Oil Conference-Canada, 11-13 June, Calgary, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2013, Society of Petroleum Engineers
- 5.2.1 Phase Behavior and PVT Measurements, 4.1.5 Processing Equipment, 3 Production and Well Operations, 5.1.5 Geologic Modeling, 6.5.1 Air Emissions, 5.4.6 Thermal Methods, 5.5 Reservoir Simulation, 4.3.4 Scale, 5.5.8 History Matching, 5.3.9 Steam Assisted Gravity Drainage, 5.1.1 Exploration, Development, Structural Geology, 5.8.5 Oil Sand, Oil Shale, Bitumen
- PID control, thermal process optimization, field-scale, CSS combine SAGD process
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Given its water consumption and greenhouse gas emissions to the atmosphere, it is critical to optimize the steam injection strategy and steam conformance in steam-based oil sands recovery processes such as cyclic steam stimulation and steam-assisted gravity drainage to minimize the steam-to-oil ratio and maximize the cumulative oil volume produced. Given the heterogeneity of oil sands reservoirs, robust adaptive oil sands processes which respond to the system to continuously shift the operation towards desired operational objectives are desired. This kind of adaptive control can be achieved by proportional-integral-derivative (PID) control. PID automated control is a relatively simple method to control well operations in thermal processes by using observed data already measured in existing steam-based recovery processes. Here, a vertical-horizontal hybrid well configuration within an oil sands reservoir, with reservoir properties previously tuned by a history-match to field data, is operated under PID control to demonstrate that automated control can yield improvements of recovery process performance. Here, the well configuration consists of multiple vertical injectors and a few horizontal producers - early in the process, cyclic steam stimulation is initially done in the vertical wells to establish thermal communication within the reservoir. After sufficient communication is accomplished, the steam is injected into the vertical wells and fluids are produced through the horizontal wells in a steam-assisted gravity drainage mode. Automated control must accomplish thermal communication between the vertical and horizontal wells and thereafter the steam must be controlled to minimize the steam-to-oil ratio and maximize the oil rate. The results demonstrate that PID control can be used to improve the cSOR and volume of oil produced.
Given its high viscosity at original reservoir conditions, sustained primary production of heavy oil and bitumen from oil sands reservoir is impossible since the oil's viscosity is typically greater than 100,000 cP. To lower the oil's viscosity to values so that it is sufficiently mobile under gravity, its temperature has to be raised to over 200?C. This can be achieved by high-pressure steam injection. Steam-based recovery processes are effective for oil sands reservoirs but suffer in heterogeneous reservoirs where steam flows irregularly into the reservoir. Interpretations from seismic information has shown that steam conformance around wells may be non-uniform and as a consequence, the steam-to-oil ratio suffers and greenhouse emissions per unit oil produced can be excessive rendering a recovery process with lower than optimal economics. The steam-to-oil ratio (SOR) is a fundamental variable of these processes since the steam is an operating cost whereas oil represents revenues. The SOR also represents the carbon dioxide emissions intensity (mass carbon dioxide emitted per unit volume oil produced) and water consumption intensity (water consumed per unit oil produced) of the process thus there is significant incentive to minimize the SOR.
Gotawala and Gates (2009) were the first to explore automated control of well injection as a means to improve the steam-to-oil ratio in Steam-Assisted Gravity Drainage (SAGD). Their results showed that proportional-integral-derivative control could be used to offset the effects of reservoir heterogeneity. Stone et al. (2011) tested SAGD in heterogeneous oil sands reservoir models with automated PID control. Their results, consistent with Gotawala and Gates (2009), demonstrated that feedback control improved the SOR and economics over the production interval and reservoir heterogeneity did not degrade the performance of the controller. In summary, the results have shown that automated control could be used to improve steam-based recovery process performance in oil sands reservoirs by improving the steam conformance within the reservoir.
|File Size||2 MB||Number of Pages||17|