This paper presents the results of several large-scale Sand Retention Tests (SRTs), which are used to test and refine the criteria used for slotted liner design. The paper also presents the analysis of test measurements to improve the understanding of the parameters that influence the sand control performance. The parameters include Particle Size Distribution (PSD), flow rate, slot opening size and slot density.
The SRT facility was commissioned to improve the existing testing methods by (1) using multiple-slot rather than single-slot coupons, (2) using more realistic sand pack preparation/saturation procedures than the existing practices, (3) measuring the pressure drop along the sand pack and across the liner coupon to assess the retained permeability and flow convergence, and (4) post-mortem analysis of the sand pack to measure fines/clay content along the sand pack as a direct measure of fines migration. Several tests were performed by varying the slot size, slot density, and PSD of the sand pack, and flow rate. The testing data were used to validate and improve the current industrial design of slotted liners.
Test measurements and observations indicate that the sand pack preparation procedure highly affects the testing results. For typical field porosities and PSDs, we observed finite amount of sand production bellow the existing criteria for sanding during the SRT, for the screens designed based on existing models. Testing data also indicate smaller retained permeability for lower slot density due to converging flow. Moreover, measurements indicate lower retained permeability for narrower slot width, caused by the accumulation of fines and pore plugging in the liner's vicinity. However, larger slot width than a certain size contributes to higher levels of sanding. Three different sanding modes are identified: (1) initial sanding or sand occurrence, (2) flow rate dependent transient and (3) flow rate dependent continuous sanding. It is proposed that the sanding mode should be also included in the design criteria along with the acceptable sanding threshold. Test results indicate the combined effect of the slot size and density on both retained permeability and sand production. These findings lead to a new design approach for maximum retained permeability and acceptable sand retention.
This paper introduces a new set of design criteria for slotted liners based on the results of a novel large-scale testing to evaluate the sand control for thermal heavy oil production applications. Also it provides a better understanding of the sand production and the role of the slot width and slot density on the sand production. The paper also presents an improved understanding of the sanding and permeability evolution close to the liner in relation to several liners and flow parameters. The set-up, testing procedures, and measurement methods that are used in the experiments improve the existing methods in several fronts.