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In the Steam Assisted Gravity Drainage (SAGD) process, the pre-heat is a very important step in the successful development of the steam chamber. The pre-heat period lasts months and is deemed complete when the temperature between the injector and producer is high enough to establish hydraulic communication. A uniform pre-heat along the wellbore is crucial to achieve steam chamber conformance throughout the life of the well pair. The efficiency of the pre-heat can be affected by several factors, with completion type being one of the most important among them. The objective of this study is to evaluate the impact of this factor on thermal efficiency during the pre-heat phase of the SAGD process.
In this study, the completion practices in five major SAGD projects in Alberta, Canada (Suncor's Firebag and Mckay River, Cenovus' Christina Lake and Foster Creek, and ConocoPhillip's Surmont) were evaluated. The critical factor used to determine the efficiency of any completion type in the pre-heat process is the heat loss and heat exchange along the producer and injector wellbores and the completion components. This variation in thermal efficiency results from factors such as concentric versus eccentric dual tubing completion, and tubular size, length and configuration.
The results of the study provide a comparison of different completion practices in the five major SAGD operations in Canada. The simulation modeling of the process, along with field experience and observations, helped to understand the impact of counter-current heat exchange and heat loss in concentric versus eccentric completions. Also, the results were used to quantitatively evaluate the impact that vacuum insulated tubing has on delivering energy to the reservoir and its associated thermal efficiency during the pre-heat process.
This paper is aimed at providing a better understanding of the impact of different completion methods on thermal efficiency during the pre-heat period in the SAGD process. The study also incorporated actual field performance of the 5 major SAGD projects available in the public domain and AER reports.
The classical SAGD (Steam Assisted Gravity Drainage) involves drilling wells in parallel horizontal pairs. Steam is injected into the upper well (injector) to heat the reservoir and mobilize bitumen/heavy oil so that it drains to the lower well (producer) and can be lifted to the surface. In this process, steam distribution in the injector and a sustainable liquid level above the producer are key to achieve steam chamber conformance. The completion designs of these wells are critical in order to achieve optimal bitumen/heavy oil recovery and steam chamber development1.
Orifice based Flow Control Devices (FCDs) are being used in the SAGD wells. The FCDs in the injector (Steam Splitters) are used to customize steam distribution along the well. The FCDs in the producer (Inflow Control Devices) are used to develop a uniform inflow along the horizontal wellbore.
In this paper, a method will be presented for determining the size and position of Steam Splitters and Inflow Control Devices. This method can be used for both simple and complex reservoirs containing geological heterogeneity, hydraulic barriers and baffles. The validation of the design by field data in a Case Study will also be presented. It is shown that using FCDs in the wellbores helps to improve conformance and performance of SAGD well pairs significantly.
The classical SAGD involves drilling wells in parallel horizontal pairs. Steam is injected into the upper well (injector) to heat the reservoir and mobilize bitumen so that it drains to the lower well (producer) and can be lifted to the surface. In this process, steam distribution in the injector and a sustainable liquid level above the producer are key to achieve steam chamber conformance. The completion designs of these wells are critical in order to achieve optimal bitumen recovery and steam chamber development.
Two common tools in SAGD wellbore completions are Steam Splitters and Inflow Control Devices. The Steam splitters are used to customize steam distribution in the injector. The Inflow Control Devices are used in the producer to develop a uniform inflow along the horizontal wellbore.
The Open Area Calculator provides a means for identifying the percentage of open area on the outside diameter of a pipe.
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