Workflow for Sand Control Testing of Injection Wells in Steam Assisted Gravity Drainage (SAGD)
ABSTRACT
This research aims at tackling a specific production engineering problem in sand retention testing (SRT). One common practice of operational oil companies is to prevent sanding by deploying standalone screens (SAS). SAS consists of slotted liners (SL), wire wrap screens (WWS), and punched screens (PS), among others. A systematic methodology was developed for SL design using the SRT for steam-assisted gravity drainage (SAGD) injectors. Although the solution is particular for the SAGD injector, the same or similar methodology can also be applied for any other injection or even production well. SRT investigation for SAGD injector flowback was considered as a demonstration for the capability of the proposed methodology in comparison to previous techniques. The previous techniques sometimes rely on hypothetical or invalid assumptions due to the lack of necessary field data to perform such a study. Often, field data are confidential and nearly impossible to obtain for a hazardous scenario like a thermal injector flowback.
The proposed methodology consists of three fronts. The first front is to estimate the laboratory testing variables or operational parameters based on case-specific data and reservoir simulations to assess the flowback. The simulation accounts for the unique reservoir characteristics that change from one field to another. The STARS module of the Computer Modelling Group (CMG) simulator was used to predict the consequences of SAGD injector flowback, which is the only possible way of sanding from a reservoir engineering viewpoint. Moreover, one of the natural gas flow correlations was coupled to the CMG model to ease the modification of production system variability by an interactive, in-house developed, excel program. The coupling reduces the computational-time from about 20 hours to less than 1 hour. The computational-time reduction was due to using a 2D-model, based on symmetry, instead of the 3D-model. Accounting for thermodynamic equilibrium changes the understanding of the problem drastically by avoiding inaccurate assumptions used in the past.
The second front is to develop a new SRT set-up specialized for SAGD injector flowback laboratory testing and maintain a cost-effective research budget. Intensive testing was performed to troubleshoot the associated problems with high-velocity gas flow. The final front was to verify the performance and efficiency of the developed testing set-up by conducting six tests. Furthermore, more representative reproducibility criteria were proposed to ensure testing repeatability.
SRT results show that the current industry practices for SL selection, which rely upon field experience or rules of thumb, are not conservative as previous researches claim. Eventually, this research should be considered as a single-step only in SRT for SAGD injector flowback, and necessary methodology enhancements and facility upgrades should be investigated in future work.
