Transcript Geomechanical model - Amazon Web Services

Reasons why some geomechanical
models turn out “unfit for purpose”
Jorg Herwanger
Geomechanics: Quo Vadis?
SPE London October Meeting
Geological Society, London-Tue. 27th October 2015
Agenda
1. Geomechanical models all have the same
building blocks …but they are not identical
2. Limiting factors for the value of geomechanical
models
– Applied technology
– Communication
– Contracts
3. The way forward?
Geomechanical models all have the
same building blocks …
… but they are not identical
What is a geomechanical model?
Geomechanical model
Geology
Mechanical Elastic + Strength
Stratigraphy
Properties
Earth Stress and
Pore Pressure
Oilfield Review, Summer 2003, Watching Rocks Change: Mechanical Earth Modelling
A geomechanical model comprises
1. Mechanical properties (including intact rock, fractures and faults)
2. Stress state, and
3. Pore pressure
This can be in 1D (e.g. along a wellbore), in 3D (the full field), and 4D (including production)
Based on the model, useful predictions for reservoir development and management are made
Geomechanical models have many applications
www.crusher.mines.edu
Jerry Meyer, PhD thesis
http://www.chevron.com/fraderesponse/
Permeability Change
Orientation + containment
Oilfield Review, 4 (4), 4-17
Fracture Tortuosity
Seal Breach
Frack growth
One Model
Many Applications
Wellbore stability
Courtesy of Saudi Aramco
Hubbert, and Willis, 1957
Bruno, M., SPE 79519
Wellbore integrity
Subsidence and Compaction
1978
1986
Limiting factors for the value of
geomechancial models
A successful project has many parents
Technology
Contracts

Communication
Many factors contribute to a successful project
There is a sweet spot, when technology, contracts and communication are ALL
executed well
And conversely …
The Liebig minimum principle
Justus von Liebig’s minimum principle states:
• The yield in agricultural production is
proportional to the amount of the most
limiting nutrient
• For example, a plant needs (i) mineral
elements (Phosphorus + Nitrates from the
soil), (ii) CO2 (from the air) and (iii) water to
grow
• Each of the three can become the most
limiting nutrient, or “bottleneck” in the
growth of plants
Minimum
Mineral
elements H2O
CO2
The “Liebig barrel” is used to demonstrate the
principle:
• The shortest slat becomes the limiting factor
for filling the barrel, and the volume of
liquid in the barrel is proportional to the
shortest slat
Minimum principle applied to GM projects
Liebig’s minimum principle re-stated:
•
The value in a geomechanics project is directly
related to the most limiting factor in the
bidding and execution of projects
Minimum
In this talk, I will share experiences of geomechanics
projects, where the value of a project was
decreased, due to a limit imposed by:
1. Applied technology
2. Poor communication
3. Contracting mechanism
I will not speak about limits imposed by
• Lack of knowledge, training and experience
…
(baseline competencies), or
Technology Communication
• Organizational structure
Contracts
If you ask me, I will offer my opinion
Limiting factors: Applied technology I
The pesky matter of scale
Applied technology as a limiting factor I
Observation by client:
• Stuck pipe during drilling
• Suspected cause: fault reactivation/bedding parallel slip
Finite element modelling of shearing of drill-pipe
After: http://www.drillingcontractor.org/studytackles-industrys-shearing-capabilities-26402
Applied technology as a limiting factor I
Observation by client:
• Stuck pipe during drilling
• Suspected cause: fault reactivation/bedding parallel slip
Geomechanical model delivered:
• 3D numerical model (cell size 100m
x 100m x 10m in region of interest)
• Looked for cells with “high plastic
strain” in region of interest
• No analysis of effect of increase in
Pp as an effect of overbalanced
drilling
• No inclusion of “planes of weakness”
such as faults/bedding planes or
attempt at failure analysis
Geological Society is in
Central London
Geological Society is on the
North Side of Piccadilly
Entrance
Both images show the location of the
Geological Society
Both maps are useful, but only one map is
useful to find the entrance?
A simple explanation for failure on a
plane-of-weakness
Effective stress change during pressure increase

DP
𝜎3′
𝜎2′ 𝜎3′
𝜎2′ 𝜎1′
𝜎1′
𝜎𝑛′
Solid black lines: Mohr circles pre-drill
Stippled black: Mohr circles with increased pore pressure due to
high mudweight
Complexity arises from determining good estimates/bounds for
effective stresses and strength properties
Limiting factors: Applied technology II
The pesky matter of building the
wrong model
Applied technology as a limiting factor II
Client issue:
Stacked reservoirs produced with water
injection
Avoid creation of hydraulic pathways
between reservoirs
Injector
A
Producer
A
Vertical compaction
Vertical dilation
Applied technology as a limiting factor II
Client issue:
Stacked reservoirs produced with water
injection
Avoid creation of hydraulic pathways
between reservoirs
Injector
A
Producer
A
It seems pretty clear what elements
need to be included into a model
Or may be not. Let’s look at the model
delivered to client
Vertical compaction
Vertical dilation
Applied technology as a limiting factor II
Client issue:
Stacked reservoirs produced with water
injection
Avoid creation of hydraulic pathways
between reservoirs
Injector
A
Producer
A
Geomechanical model delivered:
• 4D numerical model
• Lower reservoir only
My kids would call this an “epic fail”
Vertical compaction
Vertical dilation
Limiting factors: Communication
Communication as a limiting factor
The sad story of “stacked models”
• “Stacked models”, are models that
have never been looked at
Technical
Contractual
• Reasons I have encountered are:
o Key person has left the team
(without a sufficiently detailed
handover)
o Asset team too busy
Communication
o Model delivered to technical services
team, without study passed on to
asset team (asset team stating “we
did not know about the existence of
Models that are never used, despite
such a model, and we asked for
being technically sound and fit for
support”)
purpose
o Change in priority for asset team

Limiting factors: Contracts
Contracts as a limiting factor
A typical contracting mechanism for NOC’s
1. Expression of Interest (EOI) and technical
pre-qualification
2. Companies above technical threshold are
invited to bid
–
Pre-qualification run by technical team, now
contracting department takes over
3. Closed bid
–
–
–
Cheapest bidder wins
No technical qualification of bids
No assurance that the winning bid will solve
the problem, as de-coupled from statement
of technical competencies in 1 + 2
Good, fast, cheap – choose two
Contracts as a limiting factor
“Enterprise Solutions” and
“Global Service Contracts”
• May work well for rental cars and
standardized manufacturing
• May work less well for bespoke
consulting
This is not to say that partnerships
are discouraged. On the contrary,
having worked together before
(service company + oil company; or
internal services + asset team) can
markedly improve quality of service
My bespoke model: “But look it has a
different license plate / contract number”
Conclusions
Factors limiting the value of
geomechanical models
I presented three factors that can limit or destroy
the value of a geomechanical model:
1. Technology
2. Communication
3. Contracting process
Avoiding these limiting factors takes:
1. Vigilance on behalf of technical experts
2. Honesty about the status quo and
3. Clear thinking by all involved
Thank you – Any Questions
Jorg Herwanger
[email protected]
Tel: +44 (0) 208 943 9074
www.ikonscience.com