Morte, Matthew Kyle (2020-01). TESTING ELECTROMAGNETIC ENERGY PENETRATION AND ABSORPTION UNDER RESERVOIR CONDITIONS: THE INFLUENCE OF PIEZOELECTRICITY. Doctoral Dissertation.
Thesis
The potential of microwave technology in the context of enhanced oil recovery is a concept whose technical feasibility has been expounded by numerous pilot tests. However, poor penetration depth and limited understanding of dependencies of complex permittivity on the dynamic downhole environment have proven prohibitive in terms of economic viability. Addressing the concerns of relatively poor stimulated reservoir volume as a function of low penetration depths as well as illuminating dependencies of complex permittivity in the reservoir enables the industry to take steps towards economic implementation. Manipulation of absorption and penetration dynamics of the wave is achieved in this study by means of triggering the direct piezoelectric effect. Dynamic polarization of the quartz crystals in sandstone reservoirs manifests itself as a function of a differential stress imposed upon the rock. Acoustic waves are propagated into the reservoir rock where the mechanical wave nature vibrates the particles in the medium; so an additive stress on the rock is created. The direct piezoelectric effect dictates that the quartz crystals, which are a piezoelectric element, will be polarized in the presence of the mechanical stress. Therefore, simultaneously introducing an acoustic wave and microwave to the reservoir takes advantage of inherent piezoelectricity realized by the quartz crystals, increasing the penetration depth of the microwave. Complex permittivity is the parameter which governs the absorption and penetration dynamics in the reservoir and is accordingly integral to any prospective microwave treatment. Reservoir heterogeneity requires that complex permittivity be calculated both as a function of time and space as reservoir properties change during production. Dependencies of this parameter in a reservoir environment are not well understood or adequately described in literature with current estimation techniques being overly simplistic. Mixing rules employed are derived on the basis of mutual exclusivity and volumetric proportionality and are not capable of predicting the behavior in the complex downhole environment. A new estimation model is created by use of a multivariable regression of a statistically significant number of experiments. The regressed model innately captures all interactions in the reservoir and provides for a more realistic interpretation of wave propagation. All dependencies of complex permittivity are isolated and explicitly quantified with the result being a more accurate technique for predicting the complex permittivity in the reservoir. Minimal profit margins of microwave heating inhibit what is otherwise a technically viable and productive technique with vast potential. Triggering the direct piezoelectric effect in sandstone reservoirs is one way to stimulate greater volume, thereby enhancing the transmissibility of a larger volume of fluid. Also, optimization of microwave processes is performed by numerical simulation. Complex permittivity governs the microwave absorption in the reservoir and is of primary importance to any estimation model. A regressed model as a function of a multitude of measurements on unconsolidated cores provides for an accurate and effective predictor of complex permittivity as a function of reservoir properties.
