Présentations Colloques

Oral Presentation
6.01
Session 6.01: Managed Aquifer Recharge
Ben Hall
A new technique for perforating steel casing to seal and protect aquifers
A new technique for perforating steel bore casing has been designed and trialed in Victoria, Australia. The technique uses a high pressure hydraulic packer system to expand and stress steel bore casing to a point beyond it ductile strength limit to yield and perforate the casing. This allows retrospective sealing of bore annuli to protect aquifers from cross flow and contamination.**The Victorian State Observation Bore Network (SOBN) provides critical groundwater information to enable effective groundwater management. Many of the bores are very deep (131 are from 300m to 1,200 m deep), and transect multiple aquifers. Typically the deep bores are more than 30 years old, constructed with steel casing were often not fully cemented. This poses a risk to groundwater resources due to vertical leakage across aquifers. **Perforation of steel bore casing is traditionally completed by either small explosive charges or mechanical cutting. Use of explosives has a number of safety risks and potential to excessively damage casing while mechanical cutting requires the mobilisation of a drilling rig and produces perforations of limited aperture. The hydraulic packer perforating system, on the other hand, has the following advantages+ (1) it is intrinsically safe (2) it can be deployed from a small truck and (3) produces large aperture perforations which can be readily verified by caliper log or camera survey.**The hydraulic packer assembly consists of a multi-layer high yield rubber packer rated to 10,000 psi lowered into the bore to the specified depth. The packer is inflated to a pressure of 8,000 psi or until the steel casing yields. Field testing showed that the steel casing yields with longitudinal ruptures approximately 1m long and up to 0.02m wide. This perforation allows cement grout to be injected beyond the bore casing to retrospectively seal the bore annulus at specific depths, typically adjacent to aquitards. This innovative technique has allowed the completion of large scale programs of decommissioning and refurbishment in an efficient and cost effective way. ******
Australia