UPVC (Uniaxial Strain Tests)
Depletion and injection processes associated with hydrocarbon production cause volumetric deformation in the structure of the subsurface.
The induced volumetric deformation can be described by the compressibility of the rock matrix and the compressibility of the pore space housing the hydrocarbons. Compressibility is an important input in evaluating reservoir characteristics with respect to permeability estimates, original hydrocarbon in place estimates, reservoir pressure management, production planning and in anticipating compaction and subsidence related challenges.
The most common observation and assumption about the volumetric deformation of the reservoir system in the field, is the uniaxial nature of deformation. The uniaxial nature of the volumetric deformation is attributed to the lateral confinement of the reservoir by the adjacent bounding strata.
This can be replicated in the laboratory by performing a uniaxial pore volume compressibility [UPVC] experiment estimating the matrix and pore volume compressibilities under uniaxial deformation regime. The uniaxial deformation is achieved by maintaining zero lateral strain conditions.
The uniaxial deformation can be experimentally replicated under either pore pressure depletion conditions or under effective stress conditions following the ISRM Suggested Method for measuring Uniaxial-Strain Compressibility Testing for Reservoir Geomechanics.
The drained uniaxial pore volume compressibility (UPVC) is measured under zero radial strain condition (∆𝜀_𝑡=0) and constant overburden stress conditions.
To simulate reservoir depletion, the total axial effective stress is increased in discrete steps to simulate reservoir compaction while monitoring the changes in confining stress, deviatoric stress, axial strain and ultrasonic velocities (Vp,Vs1,Vs2,Vp45).
Simultaneous measurement of anisotropic permeability [KV, KH] can also be performed under the uniaxial strain regime over the duration of the experiment enhancing the understanding of permeability as a function of stress. High accuracy and low-pressure pulsation MR-FlowQube pump and high accuracy digital pressure transducers allow estimation of the vertical and horizontal permeability during UPVC test.
The UPVC tests also aid in defining the complete failure envelope of the rock, beyond the pure shear zone.
Recommended Sample Dimensions:
Diameter: 1” Length: 2”
Diameter: 1.5” Length: 3”