Abstract
Storing and recovering water, carbon and heat from geologic reservoirs
is central to managing resources in a changing climate. We tested the
hypothesis that the strain tensor caused by injecting or producing
fluids can be measured at shallow depths and interpreted to advance
understanding of underlying aquifers or reservoirs. Geodetic-grade
strainmeters were deployed at 30m depth overlying the Bartlesville
Formation, a 500-m-deep sandstone near Tulsa, OK. The strainmeters are
220m east of injection well 9A completed in a permeable lens at the base
of the Bartlesville Formation. Water was injected into well 9A at
approximately 1.0 L/s during four tests that ranged in duration from a
few hours to a few weeks. The horizontal strain increased (tension) and
the circumferential strain was a few times larger than the radial
strain. The vertical strain decreased (compression) during injection.
Strain rates were approximately 100 n/day during the first few hours,
but the rates decreased and were approximately 10 n/day during most of
the tests. Four independent methods of poroelastic simulation and
inversion predict reservoir properties and geometries that are similar
to each other and consistent with independent information about the
reservoir. All strain interpretations predict that a boundary to the
permeable lens occurs beneath the vicinity of the AVN strainmeters,
which is consistent with core data from the site. The boundary of the
permeable lens is located by matching the radial and circumferential
strains, which demonstrates the value of measuring the strain tensor.