The Chemical and Petroleum Engineering (C&PE) Department at the University of Kansas proposed a two year project to study the capability of enzyme-loaded polyelectrolyte complex nanoparticles in cleaning up the filter cake generated by fracturing fluids. Polyelectrolyte complex nanoparticles (PECNPs) have been previously demonstrated to entrap enzymes used as breakers for fracturing fluids and delay their release while being able to degrade cross-linked fracturing fluids successfully. Efficiency of the PECNPs in degrading filter cakes generated by fracturing fluid is studies using a fracture conductivity cell. Fluid loss prevention using nanoparticles is also studied during the course of this research. More efficient cleanup of hydraulic fractures in using nanoparticles will result in higher production from oil and gas reservoirs.
Reproducing the preparation of polyelectrolyte nanoparticle system and their performance in degrading gelled guar was conducted successfully and significant delay in release of enzymes from PECNPs was observed.
A fracture conductivity cell that was donated to the Tertiary Oil Recovery Program (TORP) by Schlumberger was installed, fluid loss and injection lines, pressure and temperature transducers and a data acquisition system were installed and fluid loss and cleanup procedures were developed for this setup. A baseline test using 20/40 Econoprop proppants was conducted to measure the baseline permeability of the proppant pack at different stress and temperatures.
Static fluid los tests were conducted for the nanoparticles and showed that PECNPs are significantly capable of reducing the fluid loss for hydraulic fracturing applications in reservoirs with permeability values lower than 0.1 mD.
Fracture conductivity tests will be conducted to study the fracture cleanup capability of the two PECNP systems that are loaded with enzymes. Retained conductivity induced by enzyme-loaded PECNPs will be compared with retained permeability induced by the control nanoparticle system with no enzyme, control enzyme system and a control polymer system.
Conventional techniques for the formation evaluation of organic-rich source rocks continue to leave many unanswered questions. Unconventional techniques are required for reliable petrophysical evaluation of these formations to minimize the production uncertainty. Improvements in well-log interpretation techniques can enhance estimates of hydrocarbon reserves, which have a direct impact on recovery factors of hydrocarbon production. Furthermore, a reliable, real-time, and high-resolution formation evaluation improves quality of decisions for locating fracturing or completion zones, which enhances production.
Well-log interpretation is the most practical approach for a real-time assessment of petrophysical properties in a wide depth interval. However, the results of our previous research in organic-rich source rocks revealed that conventional resistivity-porosity-saturation models (e.g, Archie’s model and Waxman-Smits model) underestimate hydrocarbon reserves, where volumetric concentration of kerogen increases. These preliminary results indicate a need to develop new well-log interpretation techniques to estimate hydrocarbon reserves in organic-rich source rocks. In this work we quantify the effect of organic matter and pore structure on electrical resistivity of organic-rich source rocks using numerical simulations of electrical resistivity in rock-fluid systems.
The pore-scale numerical simulations confirmed that conventional resistivity-porosity-saturation models can cause 8% – 16% relative errors in estimates of fluid saturations in organic-rich source rocks in the presence of 10% – 30% volumetric concentration of kerogen. The results of this research are promising for significant improvement in the assessment of hydrocarbon saturation in organic-rich source rocks using conventional well logs. The well-log-based estimates of hydrocarbon reserves can be used to detect productive zones for completion and fracturing jobs, which can potentially enhance production in organic-rich source rocks.
Reza Barati, Assistant Professor, Chemical and Petroleum Engineering Department, The University of Kansas
Reza Barati earned his PhD at the University of Kansas. He worked for the Enhanced Oil Recovery Institute (EORI) at the University of Wyoming before joining KU. His research interests include oilfield nanoparticles, characterization and simulation of conventional and tight shale reservoirs, hydraulic fracturing and horizontal drilling of unconventional shale plays, enhanced waterflooding through modification of injection-brine and CO2 Mobility and conformance control.
Zoya Heidari, Assistant Professor, Petroleum Engineering Department, Department of Texas A&M University
Zoya Heidari is an assistant professor at the Petroleum Engineering Department of Texas A&M University and is the Chevron Corporation Faculty Fellow in Petroleum Engineering. She received a Ph.D. (2011) in petroleum engineering from The University of Texas at Austin. Zoya is the director of the Texas A&M Joint Industry Research Program on “Multi-Scale Formation Evaluation and Reservoir Characterization of Unconventional and Carbonate Reservoirs”.
She is also one of the recipients of 2012 SPE Petroleum Engineering Junior Faculty Research Initiation Award to develop her research program on formation evaluation of unconventional reservoirs. Before joining Texas A&M University, Zoya worked with the Formation Evaluation Research Group at The University of Texas at Austin. Her research interests include petrophysics, well logging, borehole geophysics, inverse problems, rock physics, and reservoir characterization of unconventional reservoirs.