Monitoring porosity and permeability changes in carbonate rocks using acoustic velocities (Vp and Vs)

Abstract

Carbonate rocks represent around 60% of the hydrocarbon reservoirs in the world, and the carbonate aquifers are widely known around the world as an important drinking water source as around 20% to 25%. However the characterization of carbonate reservoir still challenging due to the lack of enough rock physics studies and carbonate complexity. One of the highlighted issues in carbonate reservoir and aquifers is that an active hydrocarbon reservoir and aquifer could change original fluids, pressure and temperature conditions. These changes may lead to an alteration in porosity and permeability. However, the expected changes still not very clear issue. Another considerable issue for the reservoir porosity and permeability changes is their detection. Several studies have proposed acoustic velocities measurements for detecting porosity and permeability changes. However, these methods still need more study. This thesis is an experimental study to improve the understanding fluid-rock interaction in carbonates rocks that lead to porosity and permeability variation as a result of hydrocarbon recovery, production and aquifers production and how to monitor these changes by the acoustic velocities. Two experiment sets were proposed. The experiments were carried by simply expose carbonate samples to deionized water in two different ways which are immersion (Experiment Set 1) and injection (Experiment Set 1) and at different periods of time. Changes in porosity permeability and velocity were detected. Changes in the tested carbonate rock samples were tracked by image analyses (including X-ray 3D CT scan, SEM, BSE and EDS), porosity, permeability and acoustic velocities measurements for the rock, and ICP-MS analysis for the fluid. Tracking techniques indicate the occurrence of two fluid-rock interaction processes , which are dissolution and precipitation. Correlating porosity and permeability changes with acoustic velocity changes was not valid here as the correlation was not very clear and it differs in the two samples. Further studies were recommended to get clearer idea about fluid-rock interaction mechanism and potential correlation between petrophysical properties and acoustic velocities.

Date of Award	2014
Original language	American English
Supervisor	Sandra Vega (Supervisor)