Sand retention testing for screen selection in soft-sand completions has become an integral component to verify the screen performance. This paper describes an improved constant flow-rate test method developed for sand retention testing. The improved constant flow rate test method simulates an erosional-type failure of the formation onto the gravel pack or screen. This test methodology allows the sand to be injected at known concentration into the brine stream, eliminating mixing and settling issues.
The constant flow rate test procedure utilizes a concentrated slurry of the formation sand in brine. This slurry is then injected into the brine flow-stream to accomplish the desired solids concentration for the test (typically 0.5-1.0%). The method allows for flexibility both in the brine flow-rate used and in the solids concentration tested. The slurry injection is accomplished in a slot-flow cell and is designed such that the brine stream erodes the particles from the face of the slurry as it is injected. The distance to the screen after the solids injection is minimized to overcome faster settling of larger particles.
The constant rate sand retention test method provides the amount of solids produced through the screen, the size of the solids produced through the screen, the retained permeability of the screen, and the pressure increase over time as the formation is deposited on the screen. Detailed in the paper is a reproducibility study that was included in order to verify the test method. Additionally, a comparison between the constant flow rate and constant drawdown test has been conducted using the new constant flow rate test method. The new constant flow rate test method has been found to have greater reproducibility than the previous method. Additionally, the constant flow rate and constant drawdown test have been found to produce similar test results with known exceptions that are detailed in the finding.
The improved constant flow rate test method provides more consistent, reproducible results to assist in determining the optimal sand control screen for a target completion.