Novel laboratory methodology for fines migration testing for SAGD wells

Abstract

The sand retention and the retained permeability or flow performance of sand control screens in unconsolidated formations are usually evaluated through the pre-packed sand retention testing (SRT) procedures. These procedures attempt to address a complex process of fines migration which influences the flow performance of screens in formations with relatively high fines content. Plugging of sand control screens and flow impairment of SAGD wells in unconsolidated Alberta's oil sands is a common problem in which the role of fines migration is prominent. Previous SRT studies for the SAGD wells did not purposefully explore the fines migration process. In this study, a set of pre-packed SRT experiments with comprehensive long-term testing procedures were conducted to simulate the fines migration process and assess the flow performance behavior of a sand screen under SAGD well conditions.The experiment results indicate a non-monotonic behavior of permeability with an initial decrease followed by an increasing trend for the near screen interval of the sand pack. It is observed that the effect of releasing fine particles from or near the pore throats on permeability is dominant compared with the retention of fine particles over the thin pore throats at the first stages of the experiments. Because of testing limitations concerning initial attachment of fine particles at pore surfaces, pore size distribution, and the amount of mobile fine particles as a function of time, most results were inconsistent with decreasing trend behavior of permeability in the field and actual core flooding observations. However, a decreasing behavior was observed by conducting a new test procedure replicating a representative worst-case flow condition in the field. As the main conclusion, the previous SRT test procedures and the design criterion should be revised to enhance the flow performance assessment of sand control screens for formations susceptible to the fines migration process.