Quentin Peter Morgan

Formation Loading and Deformation of Expandable Sand Screens

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. Introduction The slotted version of the expandable sand screen (ESS) was developed in the late 1990s. It was developed to be an openhole sand control solution as an alternative to gravel packing or standalone screens (SAS). The ESS is deployed in conditioned mud or brine in much the same way as an SAS completion, and can be expanded in the same trip. Once expanded into contact with the borehole wall ESS provides compliant sand control in much the same way as a gravel pack. The ESS has been successful in a wide range of applications, resulting in good sand control, a very low skin and high productivity. The key to achieving good performance and long term reliability is strict adherence to a “Ten Steps To Sand Control Success” methodology, which encompasses many due diligence aspects to achieve right-first-time deployment of fit-for-purpose sand control completions. When considering use of ESS, foremost in the due diligence process is evaluation of the interaction of the ESS with the rock formations. Due to its slotted nature the ESS is relatively easy to expand, but it also has relatively low collapse strength. This has often led to concerns about whether the ESS can withstand the loading from the formations during depletions and drawdown. The work described in this paper details results from large scale testing and extensive numerical modeling, which show that under most circumstances the ESS can withstand the formation loading.