Oil & Natural Gas Projects
Exploration and Production Technologies
Characterization of Turbiditic Oil Reservoirs Based on Geophysical Models of Their
Formation
DE-FC26-01BC15352
Project Goal
To develop, test, and validate a new method for the characterization of turbiditic
reservoirs based on the fundamental physics of the formation of the reservoirs.
Performer
The University of Texas at Austin
Departments of Chemical and Petroleum Engineering
Austin, TX
Project Results
The project developed a new, deterministic tool for characterizing turbiditic
oil reservoirs to complement geostatistics.
Benefits
The need for improved characterization of turbiditic oil reservoirs is timely.
The valuable reservoirs currently being explored and developed in the deepwater
Gulf of Mexico are turbidites. Such deposits, constituting the most active hydrocarbon
play in the U.S., are light oil or natural gas reservoirs found at great depths
and in relatively unexplored regions. Economic viability of these reservoirs
depends strongly on their production rates; therefore, the ability to estimate
and characterize prime locations in the reservoir is vital. Further, valuable
turbiditic oil reservoirs are located off western Africa, another location of
importance for U.S. oil interests.
Background
Turbidites are formed by the deposition of sand and clay particles from a turbidity
current, which is a subsurface, suspension-laden flow driven by the density
difference between the current and ambient fluid. The fluid mechanics of this
buoyancy-driven, multiphase flow are fairly well-understood. Researchers developed
a computational simulation of the process of deposition as function of the initial
volume of the suspension or its flow rate, its initial sediment load, and the
local topography (all can be inferred from cores, logs, and seismic data). From
the predicted pattern of deposition and the distribution of particle sizes in
the deposit, it is possible to determine the spatial distribution of porosity
and permeability at a centimeter length-scale. This information is invaluable
for running other simulations of oil recovery to determine optimal methods for
extraction of oil from the reservoir. The project's proposed method is an excellent
complement to geostatistical methods for spatial characterization of a reservoir
because it includes additional information based on the physics of the formation
of the reservoir.
Project Summary
The project:
- Developed first-principle model equations for highly concentrated turbidity
flows.
- Developed numerical methods to solve equations for the highly concentrated
flows.
- Developed simulation of flow and deposition from turbidity flows over
arbitrary and dynamically changing topography for multiple particle sizes and
multiple events.
- Identified efficient methods to determine simulation inputs (initial
sediment load, particle-size distribution, event location, etc.) to match or
honor available data.
- Developed a method to convert depositional data into petrophysical data
(e.g., porosity, permeability).
From the simulation comes a detailed distribution of the particle concentration
for each deposit or layer, from which one can produce porosity or permeability
distributions. The sum of all the events produces a layered porous medium, as
is often seen in depositional systems. The information on the porosity and permeability
can be used in flow simulators.
In practice, the resulting depositional profiles can be matched to seismic,
core, and well logs by adjusting process inputs, such as sediment load and particle
size. For example, if one has only seismic information and hence the shape and
volume of the deposit, one could run simulations adjusting the particle size
to produce the best fit to known data. With this particle size, it is possible
to produce an estimate of permeability that often is critical in effective bidding
for expensive deepwater leases. This tool provides a quantitative, physics-based
means to estimate and infer valuable parameters from subsurface/subsea turbidites.
Current Status (June 2006)
The project is completed. The final report is in progress.
Project Start: September 1, 2001
Project End: January 15, 2006
Anticipated DOE Contribution: $649,000
Performer Contribution:
$183,000 (22% of total)
Contact Information
NETL - Purna Halder (purna.halder@netl.doe.gov or 918-699-2083)
UT Austin- Roger Bonnecaze (rtb@che.utexas.edu or 512-471-1497)
The topography (left) over which 325 turbidity depositional events are simulated,
giving the total deposit (right). Note the mounding of sediment. From the deposition,
a detailed porosity and permeability map of the simulated deposit can be generated.
Permeability for a single deposition event composed of particles of three sizes.
Publications
" Lakshminarasimhan, S., "Study of the Flow and Deposition from Turbidity
Currents," Ph.D dissertation, The University of Texas at Austin, May 2004.
" Srivatsan, L., Lake, L.W., and Bonnecaze, R.T., 2004 "Scaling analysis
of deposition from turbidity currents," Geo-Marine Letters 24, 63-74.
" Bonnecaze, R.T., and Lakshminarasimhan, S., "Characterization of
turbiditic oil reservoirs based on geophysical models of their formation,"
US DOE Technical Report , June 1, 2003.
" Bonnecaze, R.T., and Lakshminarasimhan, S., "Characterization of
turbiditic oil reservoirs based on geophysical models of their formation,"
US DOE Technical Report, April 1, 2004.
" Bonnecaze, R.T., Lake, L.W., and Lakshminarasimhan, S., Final Report
on Characterization of Turbiditic Oil Reservoirs Based on Geophysical Models
of Their Formation (in preparation)
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