American Oil and Gas Reporter - July 2018 - 23

AAPG Keeps Expanding
Limits Of Geologic Knowledge
With Annual Convention
Recently, as the temperatures in Houston began to rise, I had
the opportunity to spend a few days in Salt Lake City at the
2018 American Association of Petroleum Geologists Annual
Convention and Exposition, held at the Salt Palace Convention
Center. The 101st event for the Tulsa-based organization featured
a theme of "Bridging Fundamentals and Innovation." Although
it is a little risky sending thousands of geologists to a location
so rich in fascinating geology, I was impressed with the robust
attendance and quality of papers. Some of the more interesting
topics centered on unconventional resources.
In a paper titled, "Fracturing Fluid and Rock: Best Friends
or Sworn Enemies-Nanoscale Chemical Reactions During Hydraulic Fracturing," by David P. Cercone from the National
Energy Technology Laboratory in Pittsburgh, and John Bargar
and Adam Jew from the Stanford Linear Accelerator Center
National Laboratory in Menlo Park, Ca., the authors look to advance understanding of the physical and chemical interactions
of unconventional resources and the practice of hydraulic
fracturing to achieve maximum recovery of hydrocarbon
resources. One of the key aspects the authors investigated dealt
with the chemical interactions of fracturing fluids and the rock
fractures and nanopores into which they were injected.
According to the authors, using minor amounts of acid at the
initiation of a fracturing stage can carry it throughout the rock
matrix in the stimulated rock volume to create and occlude permeability. Oxygen in the fluids can act to reprecipitate mobilized
iron and reduce nanoscale permeability. Additionally, barium in
rock and drilling fluids can react with sulfate to clog pore
throats while other ingredients in the fracturing fluid such as
ammonium persulfate also contribute to barite precipitation in
the nanopores. While they had challenges conducting pressure
pulse permeability experiments with reacted cores from the
Marcellus Shale and Eagle Ford, new testing methods are under
development that will help the program extend into other
American shale basins so that state-of-the-art scientific equipment
at the national laboratories can be used to determine additional
chemical and physical alterations of shale reservoirs from the
hydraulic fracturing process.
A poster titled, "Low Field NMR Evidence of Geo-Polymeric
Behavior of Organic Matter in Shale and the Implications on
Recovery," by Robert L. Krumm, James J. Howard and Elizabeth
Krukowski from Premier Oilfield Group seeks to illustrate how
light oil characteristics impact unconventional reservoir production.
In this work, the authors assert that the mechanism through
which light oil is stored in organic matter and how it moves has
implications for unconventional reservoir production scenarios.
The traditional view holds that this oil is found in submicron
sized pores observed in the organic matter of numerous shale
reservoir rocks where phase behavior and flow properties are
defined by established physics of confined spaces.
An alternative view suggests that the organic matter behaves
more like a plastic or polymer that can absorb certain solvents.
The combination of NMR T1 and T2 measurements illustrate

"In this work, the authors assert that the
mechanism through which light oil is
stored in organic matter and how it moves
has implications for unconventional

reservoir production scenarios.

that a portion of the light oil in a hydrocarbon bearing reservoir
rock is dissolved in the solid organic matter. Differences in the
relaxation mechanisms associated with T1 and T2 processes
hold the key to identifying the light oil that is captured in the
organic matter. The restricted diffusion component of the T2
mechanism for this captured oil generates a much faster T2 relaxation component than observed in a T1 measurement that
lacks a diffusion mechanism. Distinct T1 and T2 measurements
have greater resolution than the combined 2D T1-T2 maps that
often are used in recent studies. NMR measurements on organic-rich shale and low organic content shale under dried and oilsaturated states illustrate the fast T2/slow T1 component associated
with light oil dissolved in the organic matter, which creates
complex geopolymer behavior. Thermogravimetric analysis
(TGA) of oil saturated shales also shows that organic matter has
geopolymer characteristics. Comparisons between TGA data of
other polymers with sorbed solvents and organic matter with
sorbed oil show similar trends. For organic rich samples, oil
evaporates at higher temperatures (200-350 degrees C) compared
with the bulk boiling point (174 degrees C).
These are only a couple examples of the multiple quality
papers and posters presented at the 2018 AAPG ACE event
showcasing more than 100 years of AAPG providing access to
quality information that those working in oil and gas can use to
continue their success.
r

JEREMY VISCOMI is vice pres-

ident of global marketing for
Premier Oilfield Group in Houston and Mid-Continent regional
lead for the Petroleum Technology Transfer Council. For
almost 20 years, he has played
an integral role in many oil
and gas industry technical conferences and special events.
JULY 2018 23

American Oil and Gas Reporter - July 2018

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