CRUSHED ROCK ANALYSIS WORKFLOW BASED ON ADVANCED FLUID CHARACTERIZATION FOR IMPROVED INTERPRETATION OF CORE DATA
SPEAKER: Melanie Durand - Shell Exploration and Production Company
Speaker Bio: Melanie
Durand is a Petrophysicist on Shell’s Permian Asset. After joining Shell in
2012, Melanie has worked on projects in Brazil, Argentina, and Colombia before transitioning
to the Permian Basin. Melanie has a deep breadth of operational experience in
both wireline and core acquisition. She has a B.S. in Mathematics from the University
of Louisiana at Lafayette.
Paper AAAA
Authors: Melanie Durand1, Anton Nikitin2, Adam McMullen1,
Aidan Blount1, Brian Driskill1, and Amie Hows2
1Shell Exploration and Production Company,
2Shell International Exploration and Production
Abstract: As activity increases in the Permian
Basin and multiple billion-dollar acquisitions at upwards of $50,000/acre
continue, there is a strong incentive for E&P operators to optimize the
development in their existing acreage. Unfortunately, maximizing oil production
typically results in significant amounts of produced water. Water cuts for
individual Permian wells commonly range from 50 to 90% of total liquid
production, thus the ability to predict water to oil ratio (WOR) of the
produced fluids has a major importance for development planning (Scanlon et
al., 2017).
Petrophysicists are responsible for
fluid saturation modeling, which provides the basis for predicting WOR. Core
data acquisition and analysis are critical for developing a quantitative
petrophysical model. However, accurately measuring saturations of cores taken
from unconventional reservoirs continues to pose significant challenges
originating from uncertainties in the acquired data, assumptions used to
interpret these data and more broadly, due to increased relative uncertainty
associated with tight, low-porosity formations.
For example, the crushing of the core
samples, which is required for efficient fluid extraction in tight rocks,
causes systematic fluid losses which are not typically quantified. Instead, all
as-received air-filled porosity is commonly assumed to represent hydrocarbons
that have escaped during coring due to gas expansion. Additionally, fluid extraction
from commercially available retorting systems can have widely variable fluid
collection efficiency (<100%) resulting in significant inconsistencies
between the weight of the collected fluids and sample weight loss during
retorting experiments. The Dean-Stark technique removes not only fluids (water
and oil) but an unknown volume of the extractable organic matter, and it only
allows for direct quantification of the volume of extracted water. The
reconciliation of fluid volume as well as fluid and sample weight data
delivered by either of the two techniques (i.e., retorting or Dean-Stark)
requires numerous assumptions about pore fluid properties which are typically
not verified through direct measurements. We demonstrate that such assumptions
can lead to up to 50% uncertainty in water saturation estimates.
To address such critical uncertainties,
a new core analysis workflow using improved core characterization and fluid
extraction techniques was developed. To address fluid loss during crushing,
this workflow employs advanced NMR measurements performed on both as-received and crushed samples to
quantify fluid losses. Also, this approach uses retorting techniques with close
to 100% fluid collection efficiency specially developed for core sample
characterization. The workflow is further optimized to avoid fluid loss during
sample handling and includes repeated grain density and geochemical
measurements at different stages. As a result, the new workflow addresses
uncertainties in acquired data and better informs the assumptions for
interpreting the measured data into the desired petrophysical properties (e.g.
total porosity, water saturation). The workflow is demonstrated for a set of
Wolfcamp samples.
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