Tullow Oil Resolves Drilling Uncertainty
in Compartmentalized North Sea Reservoir
Case study: 3D modeling and reservoir simulation enable reservoir engineers
to refine understanding of depositional environment and evaluate drilling options
Challenge
Determine the flow potential
of a gas reservoir compartment
with anomalous pressure rate
as a drilling target, considering
the possibility of an isolated
fault block.
Solution
Use Petrel* Reservoir Engineering
(RE) and ECLIPSE* reservoir
simulation software to better
understand sand-body architecture and fault transmissibility,
and to evaluate drilling scenarios.
Results
Identified three viable scenarios
from 100 geologic models used
to test the sensitivity of reservoir
properties; evaluated the
effectiveness of development
scenarios; and received approval
for the drilling proposal.
Evaluate drilling locations
While evaluating drilling locations in the Southern North Sea, Tullow Oil PLC discovered
a reservoir sector in which the pressure differed noticeably from the pressure in adjacent
sectors. Tullow reservoir engineers needed to understand whether this sector had become
compartmentalized by faulting.
To ascertain whether the sector was completely isolated, the Tullow team decided to study
fault transmissibility and the sand-body architecture. An in-depth analysis was undertaken—
including a sensitivity study on channel orientation and the time frame of deposition—
to decide whether they needed to drill an additional well to reach this compartment.
Assess the geological conditions
To better understand the uncertainty in the reservoir description, especially fault transmissibility, Schlumberger Information Solutions (SIS) recommended Petrel seismic to simulation
and ECLIPSE reservoir simulation software for optimum modeling, analysis, and forecasting.
One hundred sector model scenarios were generated that varied channel orientation,
boundary conditions around the faults, porosity, permeability, and water saturation,
and which were efficiently tested via the flexible, easy-to-use subsurface workflows.
Petrel 3D image of base structure with facies superimposed.
Schlumberger Information Solutions
Case study: 3D modeling and reservoir simulation enable reservoir
engineers to refine understanding of depositional environment
and evaluate drilling options
The comprehensive Petrel modeling workflow (Tullow opted for nested workflows within
one main workflow) facilitated collaboration among reservoir engineers, geologists,
and geophysicists by allowing them to easily interact with static and dynamic data,
integrate their domain-specific knowledge, and draw final conclusions to expedite
decision making.
Zero in on the best possibilities
The rapid history-matching features of Petrel RE and ECLIPSE software dramatically
reduced the number of possibilities, providing three viable models that would form the basis
of Tullow’s development plans.
“Petrel RE increased our
confidence that we would
drill a successful well
in a questionable sector.
It was really fantastic
having a user-friendly tool
with which to forecast
and play different development scenarios.”
Alex Kirsch
Reservoir Engineer
Tullow Oil Company
Visualization of facies variation in matched models.
The ability to reduce uncertainty and make accurate predictions based on the three viable
geological realizations increased Tullow reservoir engineers’ confidence that they could
drill a successful well in this compartment. The next step was to evaluate development
plans, including options to drill horizontal or straight holes. Using the Petrel Reservoir
Engineering/ECLIPSE workflow, they were able to evaluate a number of development
scenarios, visualize well locations, evaluate projected production results, reposition the
wells, and retest.
As a result, the team confidently submitted a well proposal and obtained the necessary
approvals to move forward with a development plan designed to effectively drain the
isolated compartment.
SCHLUMBERGER INFORMATION SOLUTIONS
Schlumberger Information Solutions (SIS) is an operating unit of Schlumberger that
provides software, information management, IT infrastructure, and consulting services.
SIS enables oil and gas companies to achieve breakthrough team performance, unlocking
the potential of E&P teams to step-change their effectiveness and productivity. Through our
technologies and services, oil and gas companies can drive business performance and realize
the potential of the digital oil field.
E-mail sisinfo@slb.com or contact your local Schlumberger representative to learn more.
­
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Other company, product, and service names
are the properties of their respective owners.
Copyright © 2008 Schlumberger. All rights reserved. 08-IS-111
www.slb.com/sis