- Job Title:
- Staff Geologist - Structural Geologist
-
- Employer:
- Section for Wells and Productivity (WRK),
Department for Petroleum Technology and Drilling, Saga Petroleum
ASA, Kjørboveien 16, N-1337 Sandvika, Norway
-
- Group:
- Member of the Formation Mechanics Group
-
- Company:
- Saga Petroleum ASA is one of the world´s
largest upstream oil and gas companies, continental Europe's
only pure oil and gas production and exploration firm and Norway's
biggest listed oil company, based on proved reserves. The company
has significant reserves and production on the Norwegian and
UK continental shelves (including the Atlantic Margin). The company
also has interests in Libya, Angola and Namibia. As at May 5,
1999, Saga participated in 63 licenses on the Norwegian Continental
Shelf and was operator of 21 of these. Its involvement on the
Norwegian Continental Shelf includes participating interests
in 27 producing fields, five fields under development and eight
fields under evaluation. Saga has participated in approximately
one-third of all exploration wells drilled on the Norwegian Continental
Shelf to date. As at May 5, 1999, it participated through Saga
Petroleum UK Ltd. in 34 licenses in the United Kingdom and in
Ireland, in three of which as operator. Saga has participating
interests in eight producing fields on the United Kingdom Continental
Shelf. As at December 31, 1998, Saga's proved reserves of crude
oil and natural gas were estimated at 867 million boe compared
to 925 million boe at the end of 1997. Total proved reserves
consisted of 47% crude oil proved reserves and 53% natural gas
proved reserves. Approximately 60% of the proved reserves were
under development and approximately 40% were not yet developed.
For the year ended December 31, 1998, Saga's average net daily
production of crude oil and natural gas was 180,600 boe. In 1998,
net production of crude oil accounted for approximately 85% of
Saga's average daily production.The company is listed on the
Oslo Stock Exchange and on the New York Stock Exchange. At December
31, 1997, its market value was NOK 17 billion when Saga had approximately
1,500 employees.
-
- Saga Petroleum ASA was bought out by Norwegian
rivals Norsk Hydro ASA and state company Statoil in June, 1999.
The takeover was approved by the European Commission on July
5 and from 1 January, 2000 Saga Petroleum ASA became Norsk Hydro
ASA.
-
- Department:
- The Department of Petroleum Technology and
Drilling
-
- Section:
- The unit for Wells and Productivity works
on a broad range of Geomechanical problems. The unit aimed to
experience excellent results from the deployment of technologies
in drilling and wellbore stability projects. The Geomechanical
characterization of fractures reservoirs, using specialised geomechanics
technologies, help to optimize wellbore drainage and prevent
wellbore instabilities. Therefore, it aims to provide optimal
reservoir drainage, provide efficient and effective production
enhancement; eliminate excessive drilling and completion costs
and reduce risks.
-
- The unit specialised in Fractured reservoirs,
Insitu stress, Fault seal analysis and Wellbore stability. The
performance of low permeability, fractured reservoirs is controlled
by the in situ state of stress and by the distribution and orientation
of natural fractures and faults. Local variations in pore pressure
due to fault compartmentalization can result in large changes
in effective stress which significantly impact reservoir production.
In situ stress distribution and fault geometry are a key to detecting
and controlling the effects of these localized variations in
reservoir pressure. Fracture permeability studies using data
from a variety of drilling environments from large-scale, fault-bounded
reservoirs for oil and gas production.
-
- The ability of reservoir-bounding faults
to behave as effective fault-seals is strongly influenced by
the stress state acting on those faults. If the faults are critically-stressed,
repeated slip on these faults will reduce their sealing properties
causing hydrocarbon leakage to occur. Knowledge of the stress
field coupled with detailed fault mapping from 3-D and/or 2-D
seismic data is used to quantify some of the risks by assessing
the likelihood of faults behaving as suitable seals or leaky
faults.
-
- Insitu stress analysis required observations
of compressive, tensile and shear failures of wellbores to provide
strong constraints on stress magnitude and orientation as well
as upper and lower bounds on rock strength in situ. A broad spectrum
of analytical methods were used to fully determine in situ stress,
pore pressure and rock strength.
-
- Wellbore stability was a critical area of
study. The Oil and Gas industry sustains financial losses due
to wellbore failure of over $1 billion each year. Current drilling
and production practices do not take advantage of in situ stress
information and knowledge of the full stress tensor to design
optimally stable wellbores was made
-
- Therefore, the unit aimed to tackle reservoir
production challenges such as the assessment and exploitation
of fractured reservoirs, understanding reservoir compartmentalization
and the identification of bypassed oil and gas in mature and
depleted fields. This enables successful production in risky
drilling environments, reduce the costs associated with drilling
and increase the economic lifetime of mature reservoirs.
-
- Job description:
- Responsible for the Fracture Mechanics Section
of the Formation Mechanics Group
- Research and Development Coordinator for
unit for Wells and Productivity
-
- Project title:
- Sub-seismic Fault Prediction in the Kristin
field (North sea) by seismic attribute analysis (PixAt)
-
- Geologist:
- Dr. David A. Spencer
-
- Assignment:
- Kristin
-
- Project No.:
- AHBS31101
-
- Description:
- Use of PIXAT, a seismic attribute analysis
and fault tracking programme to make an attribute processing
and analysis study of a North sea hydrocarbon field. Work included
fault-tracking and editing, statistical modeling of fault networks,
and fault parameter calculations from attribute maps for the
Kristin field.
- Project title:
- Fault Seal Analysis on the Western Snorre
oilfield, North Sea
-
- Geologists:
- Dr. David A. Spencer, Jon Vold, Einar Sverdrup
-
- Assignment:
- Snorre
-
- Project No.:
- ASNODR33103
-
- Description:
- FAPS (Fault Analysis Projection System) analysis
on the Snorre Oil field, North Sea. FAPS is a system for the
interpretation, 3D display and analysis of faults and fault networks
using data from seismic interpretations, maps and wells. FAPS
is leading-edge fault analysis software that complements seismic
interpretation systems and can also be used to rebuild fault
surfaces from maps, allowing new analyses to be unlocked from
existing data. FAPS can quickly integrate seismic, map and well
data, add stratigraphic detail, generate reservoir juxtapositions,
calculate and calibrate fault seal estimates.
- Work also included predicting fracture orientations
for an injection well in Snorre field.
-
- FAPS:
- FAPS (Fault Analysis Projection System) or
Fault Seal Analysis is an advanced and successful technology
proven as a set of methodologies for predicting the sealing behaviour
of faults. Fault Seal Analysis incorporates algorithms and modes
of presentation that exploration and production geoscientists
need. With increasing sophistication of reservoir simulation,
engineers need to know cross-fault flow properties and need to
be able to predict these properties over a finite production
period. FAPS provided estimates of fault-zone permeability and
fault transmissibility modifiers. FAPS was used to provide a
solution to fault and fault seal analysis in both exploration
and production. Seismic interpretations alone did not usually
provide enough data to evaluate the significance of faults. Extra
stratigraphic detail was added so that across-fault reservoir
juxtapositions could be mapped and fault seal estimates made.
Failure to recognise the structural and hydrodynamic importance
of faults represented both lost opportunity and increased risk.
Add-on modules used in FAPS included MAPS (a tool for rebuilding
fault surfaces from ZMAP grids and fault polygons), Fault Seal
Analysis (the commercial workstation system for calculating the
sealing potential of faults) and Fault Populations (for statistical
and graphical analysis of FAPS fault data to predict the number
of faults below seismic resolution). 2D or 3D two-way-time or
depth-converted seismic sections on a workstation (e.g. SeisWorks,
GeoQuest, Charisma or Sattlegger ISP) provided the raw data for
FAPS. The basic seismic interpretations was stored in FAPS as
a set of line sections which was viewed (and edited) via the
Line Editor. FAPS did not require any special seismic interpretation
style or method. Interpretations were made as efficiently as
possible. The FAPS Line Editor was a very efficient tool for
fault picking and detailed near-fault horizon editing. FAPS also
imported depth-converted (or TWT) horizon grids (which usually
have associated fault-polygons) from mapping software (e.g. ZMAP,
CPS, IRAP). In these datasets the original fault segments on
vertical sections were generally discarded in the mapping and/or
depth-conversion process. The MAPS module was used to edit where
necessary fault-polygons, and by vertically correlation constructs
fault planes.
-
- FAPS fault analysis was based on interpretations
consisting of horizon surfaces from maps or cross-sections and
fault traces interpreted in cross-section. Bringing together
these two sets of information in a single, topologically consistent,
model was non-trivial. First the fault surface had to be modelled,
in the algorithmic sense, from the raw data, in this case the
(x, y, z) values of the traces picked on vertical sections. FAPS
used a proprietary grid-based method, referenced to a base plane,
that estimated the elevations at grid nodes from the projection
of least-squares, best-fit, planes through the control points.
Data points used in both the plane fitting and in the final,
weighted, estimation of values at the nodes were selected by
an octant search strategy. By modifying the numbers of points
required in each octant and by changing the weights, a great
deal of control was exercised over the resulting surface model.
This was important because it means that if the starting data
was good the fault model could be forced to honour the control
points very closely. On the other hand, if data quality was poor,
for example when fault traces are mis-tied, then it was necessary
to smooth through the ambiguities and picking errors. For good
quality data typically, RMS residuals between the modelled surface
and raw data were of order of a few metres or less, smaller than
the horizontal resolution of the seismic data.
-
- FAPS applied corrections to horizon interpretations
in the vicinity of a fault which ensured a single, consistent,
fault/horizon topology with no gaps or overlaps. The snapped
horizon contacts from the seismic lines was mapped onto the fault
grid. Every horizon offset on every line provided a measurement
of the local fault displacement, and this information was also
gridded over the fault surface to produce a displacement 'map'.
Three components of displacement (throw, heave and separation)
were all gridded and stored separately. The changes in stratigraphic
thickness across the fault ('growth') was similarly stored as
a grid over the fault surface. The resulting 3D model formed
the basis for fault and fault seal analysis, quantifying throw,
Gouge Ratio, thickness variations, reservoir overlap areas, etc.
The model also served as a template for refining stratigraphy
from seismically mappable scale to reservoir zone scale and for
computing pressure variations as projected from well information.
-
- FAPS was used for the evaluation of trap-critical
faults. It was also used to:
- QC fault interpretations from seismic data
or maps
- Test fault correlations using displacement
analysis
- Snap interpretations to fault surfaces
- Generate 3D consistent polygons on mapped
horizons
- View faults and horizons in a fully animated
3D volume
- Predict fault displacements in areas of poor
data quality
- Generate detailed fault-surface stratigraphic
juxtapositions
- Calculate sealing potential at reservoir
juxtapositions
- Calibrate seal factors with pressure data
- Verify fault-trap side seal
- Identify low-side fault traps
- Locate bypassed hydrocarbons in and around
existing fields
- Understand fluid and pressure differences
within fields
- Provide fault transmissibility estimates
for reservoir models
-
- Project title:
- Deformation of the Upper Draupne Sandstone
(Borg)
-
- Geologists:
- Project Manager - Dr. David Spencer
- Collaborators - Lars Grande, Vidar Fjerdingstad,
Tor Mellem, Lars Grande, Gareth Archard, Tore Vikaunet
-
- Contractor:
- SINTEF Petroleum research Institute and ResLab
-
- Assignment:
- Borg
-
- Project No.:
- A089FF1141000
-
- Description:
- A study of the deformation of the Upper Draupne
Sandstone to analyse its failure and possible potential for sand
production. Study was made by the use of petrography (thin section
analysis, grain size analysis, SEM), rock mechanical tests (Triaxial
Compression, Triaxial Unloading, Uniaxial) and subsequent selection
of a sample for a cavity failure test. Sample was first scanned
with the CT scanned to test for internal fracturing. Results
enable a clearer quantification of sand prediction due to reservoir
compaction.
-
- Project title:
- Structural core logging of the Gjallar
Ridge Structure (Offshore Norway)
-
- Geologists:
- Project Manager - Bjorn-T. Larsen
- Collaborators - Dr. David Spencer, Lars Grande,
Cinzia Spencer-Cervato, Morten Fejerskov, Fredrik Løset/NGI
-
- Assignment:
- Gjallar
-
- Project No.:
- A215A00011110
-
- Description:
- Structural core logging of the Cretaceous
Gjallar Ridge Structure offshore Norway. The upper part of the
core was mapped, paying particular attention to any structural
features present (fractures, faults, joints and fracture zones)
with various descriptions of their geometry, movement, number
of faults/fractures, orientation, width, displacement, drag characteristics,
deformation characteristics and other notable observations.
-
- Meetings attended:
- Structural Geology Group Meetings, Section
for Wells and Productivity Meetings, Section for Wells and Productivity
Thematic Course Meetings, Saga Petroleum General Meetings, Project
Meeting and numerous Personal Meetings with visiting academics,
companies, etc.
-
- Laboratory Visits:
- Visit to the Rock Mechanics Laboratory of
ResLab, Stavanger, Norway (Olav Byberg)
- Visit to the Rock Mechanics Laboratory of
Oilphase, Stavanger, Norway (Bjarne Arvesen).
-
- Research Projects (FoU) proposed for 2000:
-
- Project Proposal: Geomechanical Properties
of faults (6 months / NOK 278,000) - Project leader
- Geo-mechanical properties of faults will
be evaluated both theoretically and experimentally. Different
fault systems will be evaluated theoretically at different stages
of the burial history for different properties. Perform experimental
study of a fault zone (rock mechanical testing and petrographic
analysis).
-
- Project Proposal: Theoretical understanding
of geo-mechanical properties in finite element modelling (2 months
/ NOK 102,600) - Project leader
- Project would aim to assess the import parameters
that are used in Finite Element Modelling of hydrocarbon reservoirs.
It is unclear what differences, in particular values, would be
needed to get a significant variation in stress trajectory orientation.
The work would be a theoretical study based on a idealised reservoir
model and fault system. The faults can be separately modelled
with respect to the reservoir model and have different geo-mechanical
properties applied to them to note the variations in changes.
Numerous iterations of all the various properties will be necessary
to get a clear understanding of both the variations necessary
in the data and the variations resulting in the finite element
grid / stress trajectories / magnitudes etc.
-
- Project Proposal: Stress Controlled fault
modelling (4 months / NOK 611,500) - Project leader
- A Snorre license funded project called "Stress-Controlled
Fault Modeling in the Snorre Field" finished in July, 1999.
Although the potential for the successful use of Finite Element
Modelling is still possible, it was not proved by this project.
In other words, we were unable to prove that the modeling of
the stress trajectories, based on Finite Element Modeling, is
predictive of the occurrence of subseismic faults simply because
of the problems with the IRAP RMS grid, the boundary conditions
imposed by GeoTools and the tolerance levels in Algor (amongst
other things). A set of recommendations summarising these concerns
were given in a project evaluation report that suggests what
changes need to be implemented if a clearer understanding of
the role of Finite Element Modelling is used in fault modelling.
This project would aim to address these issues, based on the
knowledge that was obtained from the first project. The purposes
of the project are therefore to: Develop the Finite Element Model
grid of the Snorre Field; Identify and predict the areas of most
likely sub-seismic faults and more accurately model faults in
the reservoir model; Obtain and export the resultant data set
from the Snorre field to software used by Saga Engineers and
Geologists.
-
- Project Proposal: Large scale reservoir
behaviour (12 months / NOK 553,750) - Project leader
- This project is an attempt to address the
problems associated with predicting the large scale behaviour
of rocks during petroleum operations. This is due to incompatibilities
in upscaling laboratory results to reservoir scales as well as
different behaviour of what is expected when only looking at
cores. The project aims to: Review Geomechanical literature to
establish values for the fundamental parameters on the large
scale; Analyse the upscaling laws; Analyse field data of large
scale phenomena to either confirm or modify the results obtained.
It will then aim to investigate these phenomena by: Undertaking
laboratory work to describe the physics (mechanics) of models;
Undertake analytical and numerical models to confirm the laboratory
results. It will incorporate field data into the models.
-
- Project Proposal: Geomechanical Upscaling
(6 months / NOK 473,000) - Project leader
- This project would aim to asses an important
parameters that are used in Finite Element Modelling of hydrocarbon
reservoirs. The project may give better input to finite element
modelling by giving the 3 dimensional distribution of rock mechanical
parameters. Use stochastic modelling tool (STORM) for Geomechanical
upscaling. Related parameters like porosity are frequently modelled
by STORM. Test out an link between petrophysical parameters and
rock mechanical properties; Upscaling of Geomechanical parameters
to the relevant size of the grid you want to perform the analysis
(ECLIPSE, IRAP).
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