Applications of High-resolution Imaging and High-performance Parallel Computing in Unconventional Energy Recovery

摘要

Two shale gas rock samples,from a Middle East shale gas play and the Eagle Ford shale play, respectively,were scanned using a nanometer-scale focused ion beam-scanning electron microscope (FIB-SEM).The geometrical properties were extracted and compared.The high-resolution image data were then processed and used as boundary conditions in the pore-scale GPU-accelerated lattice Boltzmann simulator(GALBS)for permeability simulation.The GALBS is based on the lattice Boltzmann(LB) method and optimized by graphics processing unit(GPU)parallel computing.Image processing showed that although the intrakerogen pores in the Eagle Ford sample had larger pore volumes compared to those in the Middle East sample,their morphologies were more laminar,which leads to higher friction to fluid flow and consequently gives rise to lower macroscopic permeability.GALBS simulations confirmed that the permeability was at the nanodarcy(nd)level in the Eagle Ford sample,while it was at the microdarcy (d)level in the Middle East sample.Furthermore,anisotropy in the permeability tensor was observed in both shale samples.The computing speed of the GALBS is more than 1,000 times faster than the serial code and more than 10 times faster than the parallel code run on a standalone CPU,which suggests that many more samples can be analyzed given the same processing time.The combination of high-resolution imaging methods and high-performance parallel computing is a powerful tool for studying microscopic processes and upscaling.It provides for a more accurate estimation of the total stored gas and is helpful in the optimization of hydraulic fracturing treatments,which are aimed at connecting as many isolated intrakerogen pores as possible.The method presented in this study enables more accurate characterization of microscopic geometries and faster upscale transport properties,illustrating that unconventional energy recovery requires unconventional solutions.