The integration of horizontal wells and thermal oil recovery methods, such as Steam Assisted Gravity Drainage (SAGD), has enabled the economic exploitation of extra-heavy oil resources, mainly in Canada. The use of passive outflow control devices (OCDs) in SAGD wells adds steam injection points along the horizontal wellbore influencing steam placement and chamber growth; thus, potentially reducing the steam-to-oil ratio (SOR), productivity uncertainty and accelerating production.
For designing OCD installations in SAGD, we need to address two main aspects. Firstly, the interface between horizontal wellbore hydraulics and reservoir injectivity that allows determining the optimum number and location of the steam injection points. Secondly, the design of the OCD itself, which involves selecting and configuring the device with a hydraulic performance that is fit for purpose. For this study we will focus specifically on straight-orifice choke passive OCDs.
This paper presents a comprehensive design methodology for tubing deployed passive OCDs in SAGD. The completion design is carried out with a steady-state model of the injection well using a commercial thermal wellbore simulator.
The field performance evaluation of tubing deployed passive OCDs is critical for verifying the effectiveness of the design methodology and the hydraulic performance of the devices under real field conditions. The field evaluation is done by history matching the injection pressure vs. steam rate data with a model developed in the thermal wellbore simulator. A dynamic pressure gradient (under flowing conditions) in the injection string carrying the OCDs is obtained with a temperature log, taken with fiber optic technology, where the temperature data is converted to pressure by virtue of the properties of saturated steam. This approach is new for the SAGD industry.
The OCDs hydraulic field performance was successfully matched with the simulated model, which indicates the effectiveness of the design methodology, the field performance evaluation techniques and the effectiveness of the OCDs in delivering the desired amount of steam at each location.