Interrogating Shales …


Measuring Relative Permeability

EGI’s new relative permeability measurement facility enables measurement of oil and and water flow and assessment of relative permeability in these exceptionally low mobility scenarios. The concept and design of the equipment grew out of EGI’s previous petroleum engineering research topics demonstrating that matrix permeability is among the most critical properties governing recoveries of liquids from shale systems. This underscores the importance of measuring absolute, let alone relative permeability, and mandates serious consideration of surrogate permeability measurements and database systems currently being used industry-wide. For example, standard methods of measuring absolute permeability in shales entail monitoring pressure decay on crushed samples. This process, like others used in the industry today, is relatively quick and usually only delivers absolute permeability. Downsides to the crushing method include alteration of pore spaces and pathways and the lack of data about the more significant value for relative permeability. EGI has completed initial shake-down relative permeability tests on low microdarcy permeability samples. Tests have been completed in about 24-hours making this approach both time and cost effective.

Synthetic Shales

The use of synthetic shales has created a revolutionary approach to understanding reservoir characteristics. These 3D synthetic nanoporous/nanopermeable materials have precisely fabricated interconnected pore space. Permeability measurements using these siliciclastic surrogates will provide calibrations and comparisons between traditional crushed rock measurements and plug-scale flow-through measurements. Investigating the similarities and differences between the pressure decay and flow-through data, we expect to offer insights for flow preferences between two fluids, how they interact with various lithologies, the role of fractures, the contribution of induced micro-fracturing, and help to move the industry away from production based on ‘best estimate’ or ‘general ranges’ and toward more efficient liquid recovery using data that could be considered as being as close to ground truth, at least at a core scale, as possible.

How Are Synthetic Shales Made?

To create the best match for known lithologies in several producing shale systems, our 3D synthetic nanoporous materials will depend on techniques used in organic/inorganic molecular and supramolecular assembly chemistry. Collaboration with EGI Affiliate Scientist Professor Michael Bartl in the Chemistry Department at the University of Utah has led to a rigorous process for creating nanoporous structures that reflect naturally occurring phenomena. Researchers collaborating on this project have successfully developed techniques to make nano porous materials with predefined pore sizes, ranging from a few nanometers to tens of nanometers and a variety of shapes. It will be possible to change the pore arrangement (ordered/disordered) and the nature of connectivity of the nanopores. Materials will be silica based initially, and other mineralogies can be incorporated as the experiments proceed. We will also add different clays to create shales representative of various formations.

Interrogating Shales

State-of-the-art equipment and carefully constructed standards are expected to uncover academically intriguing and functionally valuable relative permeability characteristics of shales. The ability to manipulate temperature, pressure, and lithology to create reservoir conditions is expected to lead to new production technologies and completion methods. From our analyses we will build a relative permeability database calibrating our 3D synthetic nanoporous materials and rock samples from producing fields with relevant fluid pairs. Ultimately, calibrating the GRI crushed rock technique may be possible – amalgamating sophisticated science and practical necessity.

We encourage participation by CA members in the development and direction of this revolutionary Shale Research. Sponsor input will increase the database content for relative permeability for different shale systems outlining the similarities and differences of  relevant fluid pairs. This novel approach to relative permeability is expected to create values as close to ground truth as possible, at least at a core scale. Through project sponsorship, members have the unique ability to guide the research and ensure that questions pertinent to their company and their area of inquiry are adequately answered.

For more information about the new facilities and processes for examining relative permeability in shales as well as corresponding EGI Research Projects, please contact EGI Affiliate Scientist, Dr. Milind Deo.