Crisman Annual Report 2009 - Harold Vance Department of ...

Characterization of Rock Transport Properties in Tight Gas and Shale
Objectives
The objective of this work is to determine transport
properties such as permeability, porosity, and
fracture characteristics in very low permeability
rocks such as tight gas sandstone and shale. Further,
we would be characterizing stress-induced changes
in permeability in these low permeability rocks.
This would be done using the pulse permeameter
and steady-state measurements using under
triaxial stress. Generally, “Pressure Pulse Test”
is recommended in tight gas and shale reservoirs
instead of conventional “Steady State Permeability
Test”. The “Pressure Pulse Permeameter” machine
in Rock Mechanics Lab can be a good tool for
determining rock properties.
permeability/porosity check plugs to make sure the
values are precise. After calibrations and validations,
we will be ready to measure permeability/porosity
of the tight core samples.
Approach
During this month and the last month, we focused
on the accuracy of the transducers and found out
that a part of the measured leakage rate came from
the fluctuations in the outputs of the transducers.
The downstream differential transducer had a larger
rate of fluctuations. We tested the leakage rate
in different system pressures using impermeable
core plugs and determined that the leakage rates
in upstream and downstream transducers are
consistent, which means the leakage comes from a
point which connects both sections.
Accomplishments
To reduce the data fluctuation in the downstream
part, we changed the downstream transducer, then
calibrated and tested again. The leakage rate in the
downstream part decreased from 1.6 psi/hr to ~ 1.1
psi/hr. Then, since the shortest route that connects
upstream and downstream sections to each other is
the core holder, we inspected the core holder again
and wrapped the outer diameter of the rubber sleeve
inside the core holder with extra aluminum foil. It
covered the torn parts of the previously wrapped
foil, which had been generated due to shrinkage and
extension of the rubber sleeve. With these changes
made, we tested the leakage and the rates were
now 0.3 psi/hr for upstream and 0.36 psi/hr for
downstream, which are reasonable.
Future Work
Since the machine has had several changes and
manipulations, for the next month we should calibrate
the volumes and (if possible) test it with known
Project Information
1.2.6 Transport Properties Characterization of Tight Gas
Shales
Contacts
Ahmad Ghassemi
979.845.2206
ahmad.ghassemi@pe.tamu.edu
Vahid Serajian
CRISMAN INSTITUTE
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Crisman Annual Report 2009