The slotted version of Expandable Sand Screens (ESS) is easy to expand into compliant contact with the wellbore. This has numerous advantages in sand retention, completion reliability and the maintenance of high productivity. However, the use of a slotted base pipe design will limit mechanical strength.
A joint industry project was undertaken under the auspices of the Production Engineering Association. PEA 182 studied the effect on the ESS of loading at high stress in rocks of various cohesions and friction angles. The project showed that the ESS could withstand any conceivable combination of drawdown and depletion and stay within its design limits except in rocks with a very low friction angle, where excessive deformation was possible.
To ensure against use of the technology in an unsuitable formation, every proposed application is screened using either an analytical or FEA geomechanical model. The results of the PEA 182 tests were used to test the veracity of the FEA methodology. An excellent fit to the experimental data was achieved, both for unconsolidated sands and weak sandstones.
The FEA model of the ESS formation interaction is very versatile and has been used to study a number of different scenarios, such as the effect of sand/shale layers, non-compliance in washouts, solids production and time dependent effects in shales. The model uses the actual structure of the ESS. The first stage of the simulation is to expand the ESS. This ensures that the proper work hardening is included in the analysis. After expansion the mud overbalance is removed, then drawdown and depletion applied in the proper time scales.
The FEA results have also been compared to caliper data and compares reasonably well given the uncertainties in the stress field and the rock strength.