Due to the unconsolidated nature of the Athabasca Oil Sands in the Western Canadian Sedimentary Basin, it is common practice to complete Steam Assisted Gravity Drainage (SAGD) well pairs with the use of standalone screens (SaS's). The sizing of the liner/screen types are commonly determined by: first, getting a particle size distribution (PSD) by dry-sieve analysis and/or Laser Particle Sand Analysis (LPSA); and second, running a number of prepack Sand-Retention Tests (SRT's).
In this Nexen Long Lake study, five batches of unconsolidated McMurray Formation sand were collected from six different cored wells. Using these batches of sand, more than twenty SRT's were run with a variety of fine-tuned modifications to the traditional test protocols to best duplicate fluid production conditions as observed in the field. Some of these modifications included: altering the injected fluid/gas rate and reconfiguring the order in which the fluids / gas were injected.
The SRT results were then plotted to identify if they passed the general criteria for a successful sand control device design. Unexpectedly, many of the SRT results did not meet the pass criteria for solids production and therefore, altered the direction in which future tests were run. However, when reviewing the solids production with the cumulative fluids / gas injected, the outcome commonly reverted to being favourable.
Understanding the laboratory derived test results, and how they applied to the field, was instrumental in the lab testing process. By redefining the tests results and pass/fail criteria, based upon observed in-situ production conditions, it was possible to make both qualitative as well as quantitative analysis and therefore, more confidently decide on the optimal reservoir completion type.
The study discusses an alternative approach to interpretation of conventional SRT results relative to observed field production conditions and how ultimately, this analysis influenced the choice of liner/screen sizing selected for implementation in future Long Lake field development projects.