In situ static elastic properties assessment and validation with pressuremeter testing using a formation tester tool
Year: 2024
Type: article
Abstract: Pressuremeter testing (PMT) is a formation test that consists of inflating a cylindrical packer inside a borehole while measuring the radial deformation or injected fluid volume as a function of packer pressure. Provided that the stiffness of the packer measuring system is known and large enough compared to that of the formation, changes in packer pressure associated with changes in injected fluid volume provide a direct measurement of formation stiffness. In turn, the in situ static shear modulus is obtained from the formation stiffness at a length scale similar to the length of the packer. Here, we report on the first field-scale campaign of PMTs in deep boreholes using a wireline formation tester (WFT) tool. We carried out PMT measurements as part of the characterization and appraisal of potential sites for a deep geological repository for radioactive waste in Switzerland. PMT-derived static shear moduli results are consistent with static shear moduli derived from sonic logs using independent dynamic-to-static elastic moduli transformations. PMT-derived static shear moduli and laboratory-derived static elastic moduli using samples from coring performed at the depths of the PMT stations show consistent values, with slightly lower laboratory values. Furthermore, we report static-to-dynamic shear moduli transformations by using laboratory-scale data obtained on cores and field-scale derived from sonic logs and PMT. We report comparisons between static and dynamic shear moduli at both laboratory scale using cores and field scale using sonic logs and PMT. These first results show the viability of in situ PMT in deep boreholes with a WFT tool, as it can be performed at multiple depths in a single run, in a time-efficient manner, and in combination with micro-hydraulic and sleeve fracturing stress tests for an integral approach to in situ geomechanical assessment.
Language: English
Topic: Rock Mechanics and Modeling
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,480
OpenAlex ID: W4404901753