Monthly Luncheon Meeting
Thursday – September 19, 2019
One Shell Square/Whitney Hancock Building
701 Poydras St, Room 1891
New Orleans, LA 70130
11:30 – 1:00 pm
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CRUSHED ROCK ANALYSIS WORKFLOW BASED ON
ADVANCED FLUID CHARACTERIZATION FOR IMPROVED INTERPRETATION OF CORE DATA
Presented By: Anton Nikitin
Petrophysicist, Shell Exploration & Production Co.
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
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
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.