Maersk Oil’s technical capabilities in the fields of geology, geophysics,
geochemistry, petrophysics and reservoir engineering are key to discover
new hydrocarbon reservoirs and to unlocking the potential of its assets. The
company’s experience covers the value chain from exploration to production,
with techniques from geophysical data acquisition and processing to
innovative integrated subsurface workflows.
Maersk Oil has developed a range of in-house geophysical
technologies and matured integrated subsurface workflows that
make the most of the full range of available subsurface data.
The applications of these tools range from the evaluation of the
petroleum potential of basins to reliable pre-drill prediction of
reservoir quality. Key to Maersk Oil’s success is the integration
between the different subsurface disciplines and data types,
as well as collaboration with research centres and technology
Maersk Oil’s seismic data acquisition team is responsible for
the project management of the company’s geophysical data
acquisition projects worldwide. It ensures that seismic data
acquisition is tailored to the needs of the business unit and is
- Prepares and sends out invitations to tender documents for 2D, 3D and 4D surface seismic data acquisition projects.
- Evaluates and prepares technical and financial award
recommendations for seismic data acquisition contractors
for the responsible asset team.
- Leads project management and execution of the seismic data acquisition survey, including:
– Managing permits to shoot
– Manning seismic vessels with company and fishing representatives
– Arranging HSE audits of seismic vessels
– HSE monitoring of seismic contractors and reporting of HSE statistics to each country’s relative HSE departments
– Monitoring of budget and reporting budget to asset teams
4D seismic data
4D (3D through time) seismic data has consistently proven its
value for increasing hydrocarbon recovery by improving decisions
on infill well locations and reservoir management. Maersk Oil has
applied 4D methods to multiple fields in the Danish and UK North
Sea, with further projects in progress and planned.
4D is an integrated activity requiring the close cooperation of
multiple disciplines. Maersk Oil staff has significant experience
in all aspects of 4D, including rock physics, geophysics,
geomechanics and reservoir engineering, and have developed
proprietary tools to support 4D analysis.
The value of Maersk Oil’s 4D work can be seen e.g. in the Halfdan
field, offshore from Denmark. Reservoir pressure maintenance
and sweep of oil with water are the main objectives of the
waterflooding of the field. In 2005, after five years of production,
a repeat seismic survey was acquired, covering the developed
area. Analysis of the seismic data revealed significant changes in
acoustic impedance (IP) of the reservoir, reflecting both the effect
of the waterflooding of the reservoir and local pressure depletion.
The seismic observations confirmed the modelled behaviour
of the Halfdan Field waterflood that until then had only been
verified from indirect observations. The repeat survey provided
direct and independent evidence of parallel injection fractures
formed across the field and aligned with the injection well pattern,
showing that production performance was in agreement with
The 2012 repeat seismic survey revealed the continued lateral
movement of the waterflood away from the injectors. The survey
also showed that the depleted areas of 2005 now received
sufficient pressure support by producers converted into injectors
as well as waterflood performance of wells drilled post-2005.
This data is being used to identify areas for well interventions and
workovers to improve the oil recovery.
Dedicated Seismic Processing Centre
In 2010, Maersk Oil awarded a three-year contract to CGGVeritas
to provide an in-house Dedicated Processing Centre (DPC) at
its Copenhagen headquarters to strengthen and streamline its
seismic processing capabilities.
The conventional way of processing seismic data is to define
the technical scope of work on a project-by-project basis. Once
this is done, an invitation to tender is sent to a list of external
geophysical contractors, and the contract is awarded to the
company offering the best combination of technical capabilities
Although external projects remain an important component of
Maersk Oil’s seismic processing strategy, the DPC provides a
radically different framework. After a thorough selection process,
a geophysical company is awarded a multi-year contract with
staff, software and hardware installed within the premises to
provide on-demand processing services.
At Maersk Oil headquarters, the four full-time CGGVeritas
employees of the DPC are located next to the Geophysics group
in the Corporate Technology and Projects department. This
physical proximity is one of the major advantages of the DPC
model, allowing for much closer interaction than is possible with
external projects. Furthermore, the DPC contract, once set up,
allows for processing work to start as soon as a need has been
identified, reducing project turnaround times significantly.
Through this close collaboration, Maersk Oil has access to the
most advanced seismic processing technology and expertise
CGGVeritas has to offer, as well as an ultra high-speed link to the
world-class CGGVeritas computing hub in London.
The DPC allows for
processing work to start
as soon as a need has
been identified, reducing
project turnaround times
Time/Depth Conversion 'COHIBA'
COHIBA is an innovative depth conversion approach incorporating
horizontal well data. Maersk Oil is working closely with the
Norwegian Computing Centre (NCC) to develop depth conversion
software that exceeds the capabilities of conventional
applications. The accumulated positioning and zonation error
of long horizontal wells can become significant, and the COHIBA
approach is designed to work with these errors. Intelligent use of
the information from multiple wells, and other sources, allows the
depth conversion uncertainties to be minimised and quantified.
The name COHIBA was inspired by the keywords: COrrelation,
Horizons, Intervals and BAyesian Kriging. The method
poses the depth conversion problem in a robust statistical
framework. Moreover, the collaboration with the NCC facilitates
enhancements so that COHIBA generates depth models
which simultaneously honour a variety of data observations:
seismic interpretation, velocities, well trajectories, markers and
zones. The data has associated uncertainties and, along with
geostatistical constraints, COHIBA determines the resultant
probability distribution of horizon depths.
Similarly to Jigsaw, Maersk Oil’s proprietary inversion software,
a script-based approach automates the COHIBA process, and
allows rapid and consistent updates of the depth model as
new information becomes available through the life of the field.
The technical advantages available to Maersk Oil through using
COHIBA, in addition to commercially accessible packages include:
- The ability to calibrate to multiple horizontal wells in addition
to other input data
- Explicit management of the interdependency of multiple
- The capacity to process structurally complex models, which
may contain erosion, pinch-outs, thin layers and onlapping
- A choice between compatible deterministic and stochastic
outputs, taken from the same probability distribution
- Robust quality control mechanisms analysing all
input, filtering erroneous data and reporting potential
inconsistencies between inputs
Seismic Inversion JIGSAW
Jigsaw (Joint inversion of Geostatistics, Seismic and Wells) is an
innovative and unique inversion tool for integrated geoscience,
developed by Maersk Oil. Seismic inversion is a vital technology
for incorporating highly heterogeneous parameters, such as
carbonate porosity, into a reservoir model. Maersk Oil’s scheme
has been designed from the base up in order to provide rapid,
repeatable inversion of large datasets (both pre- and post-stack)
while allowing for the integration of different data types (seismic
reflection data, vertical, deviated and horizontal wells, stacking
velocities, for example) and iterative workflows involving
geophysicists and interpreters.
Jigsaw has, since its operational deployment in late 2010,
revolutionised the way in which Maersk Oil performs seismic
inversion, thanks in part to its class-leading speed. As an
example, a single test run of post-stack inversion over the
massive Al Shaheen field in Qatar used to take three weeks with
commercial software; with Jigsaw, the same run takes only
three hours on a standard PC.
This speed has been achieved without compromising on quality,
through a completely new algorithm designed specifically
to take advantage of modern, parallel multicore computer
architecture and large memory capacities. Jigsaw is designed to
handle extremely large problems, beyond the capacity of more
commercial tools, such as joint pre-stack elastic inversion over
a field the size of Al Shaheen, or regional surveys over numerous
fields in the Danish North Sea.
Jigsaw offers Maersk Oil a number of capabilities not found in
conventional seismic inversion software. A good example of
this is the 4D geostatistical time strain inversion, which inverts
repeat datasets that are misaligned owing to production-related
seismic velocity changes. The Jigsaw time strain inversion not
only aligns these images in readiness for further analysis, but
also recovers the part of the 4D signal that occurs over longer
vertical scales than conventional seismic methods can see.
These long-scale features are combined with fine detail from
the inversion of seismic reflections, optimising resolution,
reducing artefacts and yielding a truly quantitative measure of
Jigsaw results are used extensively within Maersk Oil and by
its partners for interpretation and geomodelling. The Jigsaw
technology is owned exclusively by Maersk Oil and continues to
be developed in house. Ownership of the software offers Maersk
Oil the flexibility to tailor its functionality quickly and easily for
the particular geoscience challenges it faces.
JIGSAW inversion results over the Chissonga discovery offshore Angola,
showing sand presence at different reservoir intervals
Reservoir quality evaluation
Maersk Oil uses a multidisciplinary approach to Reservoir
Quality (RQ) evaluations involving petrophysics, core analysis,
petrography, sedimentology, basin modeling and diagenetic
modeling. This approach has been highly successful, with predrill
predictions accurately matching post-drill results.
RQ technologies provide solutions to pre-drill exploration challenges
such as reserve calculations, flow rate estimates and risk analysis,
and post-drill development and appraisal issues, such as rock/log/
seismic calibration, pay definition, reservoir compartmentalisation,
reservoir facies trends and formation sensitivity.
Given industry bias towards exploration and development of
deep, diagenetically altered reservoirs including High Pressure,
High Temperature (HPHT) targets, RQ predictions have become
a critical component of reservoir risk analysis.
However, with the introduction of diagenetic modeling
simulators, RQ specialists have been able to provide the oil and
gas industry with predictive capabilities that did not exist a
decade ago. Maersk Oil uses commercial RQ modeling software
packages such as Exemplar™ and Touchstone™ for 1D modeling
and Tmap™ for 2D and 3D modeling.
Maersk Oil has developed some unique and proprietary methods
and workflows to ensure that RQ modeling software is able to
provide accurate and reliable pre-drill predictions. Maersk Oil has
successfully used the technology in a variety of settings, including
the Gulf of Mexico, offshore Brazil, Angola and the North Sea.
Integrated deepwater workflow
The team developing Maersk Oil’s first operated deepwater
discovery, Chissonga, has established an industry best practice
workflow that aims to define the full range of Stock Tank
Oil Originally In Place distribution and recoverable volumes.
Prohibitively expensive drilling costs prevent widespread appraisal
of all potential reservoir compartments in a complex stratigraphic
and structural system, ensuring that significant uncertainties
remain in the current development planning phase.
The integrated workflow combines detailed observations of
Amplitude Versus Offset (AVO) character, direct hydrocarbon
indicators and geophysical rock properties with detailed
stratigraphic and structural definition from 3D seismic
interpretation, in order to define 3D geometric frameworks
with integrated reservoir characterisation and ranges in fluid
distribution. Reservoir model properties are derived from seismic
and core-based facies determinations, in conjunction with well
and core data. Reservoir model properties are also quantified
using volume-based seismic conditioning from AVO-derived and
probabilistic inversion techniques.
The aim of the workflow used on Chissonga is to quantify the
ranges of recoverable volumes and predicted performance by
varying all potentially uncertain reservoir parameters (such
as net-to-gross, oil-water contacts, fault transmissibilities). In
particular, the workflow addresses a major uncertainty in this
type of depositional environment – the timing of the water
breakthrough. The workflow also accounts for dependencies
between individual reservoir parameters such as the impact
of varied porosity on permeability and therefore hydrocarbon
saturations. Static model-based uncertainty is tied to dynamic
model-based uncertainties at a common scale through the use
of software that ensures uncertainty ranges are consistently
applied and varied throughout the workflow.
Petroleum systems analysis
The petroleum systems group in Maersk Oil uses industry
standard workflows to assess the hydrocarbon potential of a
sedimentary basin, with particular focus on source rock presence
and quality, oil-source and oil-oil correlation and modelling
of prospects’ access to charge.
Geochemical data derived
from source rock, and oil and gas analyses are interpreted
to characterise and model the different petroleum systems
elements and processes occurring in the subsurface over the
geological history of a basin.
Maersk Oil uses modern techniques such as GC-MS-MS,
GC-IRMS and multivariate statistical analysis in order to
characterise or ‘fingerprint’ hydrocarbon liquids and gases. This
allows it to accurately identify where the fluids came from in the
subsurface to reduce the risk involved in finding hydrocarbons.
Petroleum geochemistry is used across exploration, appraisal
and development projects at Maersk Oil and is a major input
to play analysis, production allocation, reservoir connectivity
assessments and basin modelling.
Basin modelling allows Maersk Oil to understand the possible
generation-expulsion-entrapment history of hydrocarbons in
a basin by numerically assessing the quality and temperature
history of one or more source rocks. To do this, basin models are
calibrated to maturity parameters, such as vitrinite reflectance
identified by analysis of rock samples from wells and to well
temperature data. Currently Maersk Oil uses PetroMod and
the Zetaware suite of products (Trinity, Genesis) for petroleum
Because basin modelling essentially creates a 4D (3D through
time) model of the subsurface, it provides key inputs to prospect
evaluation, play analysis, and pore pressure and temperature
prediction thereby providing solutions to exploration and safety
questions, both pre- and post-drill.
Non-equilibrium hydrocarbon traps
Maersk Oil developed the understanding and the modeling tools
that predict the conditions and distribution of hydrocarbons in
non-equilibtrium hydrocarbon traps. This has allowed Maersk
Oil to optimise appraisal programmes and develop reservoir
simulation abilities used in the production of non-equilibrium
In the standard model for hydrocarbon traps, the contact between
hydrocarbons and water is assumed to be relatively sharp and
horizontal. The Pressure, Volume and Temperature (PVT) properties
of the hydrocarbons are assumed to be relatively constant and
in thermodynamic equilibrium. The assumption underlying the
standard model is that the equilibration of hydrocarbons in the
subsurface occurs at a speed similar to the imposed changes
caused by geological forces over geological time.
In the case of very large or low permeability hydrocarbon
reservoirs, hydrocarbons are left in a state of non-equilibrium
as they adapt at a much slower rate relative to the changes
affecting the hydrocarbon trap (imposed by burial, uplift, tilting,
migration, delayed compaction of the aquifer, temperature
gradients, change of aquifer salinity and so on).
Maersk Oil’s home base, the North Sea Chalk reservoirs, is a
prominent example of a region with non-equilibrium reservoirs
caused by a combination of delayed compaction of the chalk
aquifer, ongoing burial and local tilt of traps post early migration.
The low permeability of the chalk causes significant transition
zones above the oil-water-contact to develop. The value of
these in-house tools was clearly demonstrated when Maersk
Oil discovered the Halfdan field in the late 1990s using its
understanding of non-equilibrium traps.
Maersk Oil also applied these tools on the giant Al Shaheen
field in Qatar which had been shunned by other operators
as economically unviable. Early studies established that the
Al Shaheen hydrocarbon accumulations in low permeability
carbonates were partly controlled by regional hydrodynamics and
slow re-equilibration of the hydrocarbons in the trap imposed by
regional burial/tilt of the Qatar Arch, causing the hydrocarbons to
As an industry leader in extended reach horizontal well drilling, Maersk Oil has pioneered horizontal drilling techniques. These techniques have been instrumental in producing cost-effectively from, for example, the low permeability chalk reservoirs in the Danish North Sea.
We are constantly developing techniques to improve our drilling capabilities. In addition to geosteering, well bore positioning and surveying, and well completion and stimulation technologies, we have special capabilities within deepwater drilling and high pressure high temperature drilling.
Maersk Oil has ongoing exploration and appraisal drilling
programmes in West Africa in water depths of up to 1,500
metres, and interests in the U.S. Gulf of Mexico. In such water
depths, dynamically positioned DP drilling rigs are used. Some
rigs have dual derricks to maximise operational performance.
Drilling and evaluation of a DW well can take over 100 days
depending upon the depth of the well, the pressures that will be
encountered and the amount of evaluation that is required. The
evaluation programme can involve logging while drilling, taking
surface samples of drilled cuttings and taking core samples
from the reservoir sections of the well. To prove that the oil and
gas from the reservoir is mobile, a production test is performed
which involves flowing the hydrocarbons up to the rig.
The cost of DW wells is significant and can exceed USD 100
million. Operations require long-range logistical support from
boats and helicopters, often in isolated regions of the world.
Enormous efforts are taken to ensure that the plan is
thoroughly prepared and safely executed. At the same time
contingencies are put in place and people are trained to react
decisively if a problem occurs.
A formal planning tool called the Well Delivery Process WDP has
been established to ensure that DW well design and execution
plans are optimised. The WDP involves specific stages where
reviews are required. The reviews involve close collaboration
between subsurface, drilling and logistics teams at each stage of
the planning process.
High Pressure High Temperature capability
Maersk Oil has gained significant experience from operating
HPHT drilling programmes in the UK and Danish Sectors of
the North Sea. Reservoir pressures of up to 15,000 psi can be
encountered during drilling operations.
HPHT wells are designed using the latest well design software.
Expertise in the knowledge of materials and metallurgy is
essential to ensure that extremely high pressures can be safely
contained by the multiple steel casing and wellhead systems
at elevated wellbore temperatures. Some reservoir fluids can
have corrosive properties and the wells must also be designed
to withstand deterioration when they come into contact with
corrosive elements from the well.
Well bottom hole temperatures over 200 deg C create
enormous challenges for reliability of electronic equipment used
for reservoir evaluation.
A team of HPHT well design experts work closely together in the
UK and Copenhagen to ensure that appropriate assurance of
the well designs is performed, thus providing the safe operating
envelope for the entire lifetime of the wells.
Extended reach drilling
Maersk Oil has become an industry leader in extended
reach horizontal well drilling by developing superior skills in
geosteering, well bore positioning and surveying, well completion
Maersk Oil pioneered the application of
horizontal drilling techniques in the North Sea and has become
expert in the development of closely spaced long horizontal well
line drive patterns. Its expertise and capabilities in this area has
enabled Maersk Oil to unlock oil and gas from tight fields.
Horizontal wells were introduced in 1987 in the tight chalk of
the Dan Field, offshore Denmark. Since then, horizontal drilling
technology has been adopted by the industry as the preferred
technology for developing tight reservoirs. The Halfdan field,
offshore Denmark, and the Al Shaheen field, offshore Qatar, were
both developed using horizontal wells which included several
dual lateral wells. This enabled the wells to cover a larger amount
of the reservoir and saves a number of slots on the platforms.
Maersk Oil has been an industry leader in geosteering through
complex carbonate reservoirs for 25 years. It has developed a high
level of in-house experience in geosteering using high-resolution
bio-, litho- and sequence stratigraphy combined with fine-scale
The workflows include rigorous integration of
stratigraphic information, cuttings data and when available, logging
while drilling LWD data.
The quality and value of information gathered along horizontal
wells while drilling requires detailed preparation, discipline
integration and experience since the data is crucial for
optimising well steering and positioning.
To ensure the necessary flexibility and the ability to make
rapid decisions, Maersk Oil makes sure that a high level of
empowerment and decision making takes place on the rig
during drilling. This allows the drilling and optimal positioning of
very long horizontal wells and is an important prerequisite for
an effective appraisal of flank areas or thin oil columns using
For the record-breaking 12.3 kilometre well in the Al Shaheen
field, geosteering was applied throughout the entire reservoir
section with assistance from LWD data. A complete suite
of formation evaluation information such as gamma ray,
azimuthally-focused laterolog resistivity, bit resistivity, porosity
and bulk density was utilised to make real time geosteering
In the Al Shaheen field, Maersk Oil succeeded in placing 95%
of the ultra-long reservoir sections in targets less than 10 feet
thick. Some wells we turned some 90 degrees while geosteering
within the 3-6 feet thick target.
3D visualisation of the horizontal well pattern in the Al Shaheen field, offshore Qatar.
Multilateral well technology is nothing new to the oil industry
but the level of complexity has increased, especially in the
functionality of wells. Many operators will have good production
rates without performing a stimulation of their reservoirs and
therefore Multilateral wells can increase reservoir contact
In Maersk Oil Qatar, several Multilateral wells were
drilled where barefoot holes have been stimulated prior to
running the actual completion. However, with the extended
reach wells drilled here, the reservoir contact is somewhat
maximised by different means.
Most Maersk Oil Multilateral wells in Denmark are dual-laterals.
The main reason for this is to manage the risk versus reward
as for each junction, the complexity increases. This is evaluated
for each project or well independently. The increased cost and
risk exposure are rewarded by the increased reservoir contact,
which has been as much as twice the size of reservoir sections
measuring around 13,000 feet.
Another reason for choosing a Multilateral design could be a
limitation in surface footprint or, as for Maersk Oil, a limited
number of slots from a certain location. It can also be a
conscious economic decision when designing offshore facilities
for a field development plan as was the case with Halfdan North
East. This field is a thin chalk gas reservoir that was developed
with a mixture of single and dual-laterals in a spiral pattern for
optimal reservoir contact. Here, Multilateral technology, together
with the CAJ stimulation technique was applied to target the
entire reservoir from a single location. The Multilateral systems
are RAM level 5 which ensures pressure integrity at the junction
so each lateral can be stimulated individually.
Maersk Oil has created a suite of innovative tools designed to improve reservoir contact and increase well productivity. Many of these tools are patented.
Unlocking challenging fields, such as those in the Danish North Sea and offshore Qatar, demands more than just drilling extended reach horizontal wells. We have developed completion and stimulation technologies to overcome tight reservoirs. And for long wells, we apply innovative approaches to well monitoring and intervention.
Perforate, Stimulate, Isolate
In cooperation with a service company, Maersk Oil developed
a well completion system and installation technique that
perforates, stimulates and isolates a well zone in one single
operation, thus saving time and money.
PSI comprises a cemented liner, multiple packers and sliding
sleeves to divide the horizontal well into typically 10-20 zones.
Each zone can be open and closed using coiled tubing or
wireline tractors allowing for individual stimulation treatment,
chemical conformance treatments or closing of water or gas
While the main purpose of this system was to enable multiple
stimulation treatments along the horizontal well bore, it also
proved beneficial in reservoir management because zones could
be opened and closed for production or injection.
The system is today being combined with remotely operated
sliding side doors, moving the control of the zone isolation
system to the surface, saving money on production logging and
interventions. The intelligent operation of the sleeves provides
individual zone quality data which is used to optimise well
Sand-propped hydraulic fractures
Maersk Oil began using sand-propped hydraulic fractures in
horizontal wells in the late 1980s as an alternative to acid
fracturing, which sometimes led to a collapse of acid fractures.
The technique has allowed other low permeability reservoirs
than carbonates to be developed.
The technique involves filling hydraulic fractures with sand to
prohibit a collapse. The tail of the sand being pumped into the
fracture contains resin to solidify the sand and to prevent it from
being produced back. Alternatively, ceramic screens can be used.
Up to two million pounds of sand is pumped into one fracture. A
normal horizontal well may contain up to 20 propped fractures
along the well bore. The open fractures are typically 400 feet in
diameter and, combined, they create a large drainage area within
Controlled Acid Jet
Controlled Acid Jet (CAJ), a well completion system, has helped
Maersk Oil access reserves that would have been otherwise
uneconomic using conventional horizontal well technology.
Examples include the Al Shaheen field, offshore Qatar, and
flanks of the Dan, Halfdan and Tyra fields, offshore Denmark.
CAJ has been developed and patented by Maersk Oil.
Long horizontal wells in thin tight carbonate reservoirs are
efficiently stimulated by injecting acid into the formation,
creating a few “wormholes” as the acid dissolves and thereby
increasing the reservoir contact area. CAJ is implemented
through a non-cemented liner, with a number of unevenlyspaced
perforations that ensure efficient acid stimulation of
the complete reservoir section.
The CAJ liner has in several ways set new standards for the
completion and stimulation of long horizontal wells. The most
significant is the remarkably effective acid coverage with
efficient stimulation of reservoir sections up to 14,400 feet in a
single operation. This is more than 20 times the interval length
covered during matrix acid stimulation in a traditional cemented
and perforated liner.
The CAJ liner completion and stimulation concept has
proved efficient, simple to install and very cost effective. The
production performance of the wells completed with the CAJ
system is superior to the performance of wells completed with
Maersk Oil recently developed novel ceramic screens for horizontal
well completions, eliminating the need for resin-coated proppants
and so reducing the environmental impact of fracturing operations.
The ceramic screens are resistant to erosion even when placed
across a short perforation interval the fractures are created.
The PetroCeram™ screen, developed by Maersk Oil and a technical
ceramic specialist company, offered a breakthrough in sand control
technology, especially under demanding conditions where abrasion
is a major challenge. The screen is effectively a stack of ceramic
rings packed tightly enough to keep sand out but loosely enough
to let oil through. The solution’s novelty comes from the choice of
technical ceramic, rather than metals, whose unique properties
make it so robust it is normally used in bulletproof armour.
PetroCeram™ screens help reduce the need for workovers and
have already been responsible for the restart of one well that
had been previously chronically affected by erosion and shut
A sleeve over PetroCeram™, a screen made of stacked ceramic rings.
Fracture Aligned Sweep Technology
The Fracture Aligned Sweep Technology (FAST) concept,
developed by Maersk Oil, optimises water injection in dense
well patterns by raising its efficiency and reducing the risk
of short circuiting between long and very closely spaced
Maersk Oil has seen an increased oil
recovery rate and decreasing gas-oil ratio at fields where FAST
has been applied.
The FAST concept was first implemented on the Halfdan
chalk field in the Danish North Sea with horizontal wells
drilled 600 feet apart in a parallel pattern of alternating
producers and water injectors within 10-15,000 feet long
reservoir sections. Fracturing of the injector wells is key to the
process of voidage replacement, due to the low mobility of
water compared to oil and gas.
FAST uses the principle that fluid flow in low permeability rocks
affects reservoir stresses. The horizontal section is preferentially
drilled in the direction of the maximum horizontal stress.
Before propagating a fracture, the prevailing pressure field
is manipulated through a period of injection below fracture
propagation pressure and simultaneous production from the
neighbouring wells. At slow propagation rates, the pressure
diffusion from the fracture itself increases the alignment of the
fracture with the injection well; the technique works because the
injection rates are actively controlled.
Confinement of injection fractures along horizontal injector
wells is verified by production data from areas where FAST
has been implemented. After several years of injection, water
breakthrough to the neighbouring producers has not been
FAST uses water injection to force oil in the reservoir towards a producing well.
Around 80 wells in Denmark and Qatar have been completed with
smart well technology – surface-controlled valves that regulate the
inflow of fluids to and from the reservoir to the well and downhole
sensors that monitor the well and reservoir temperature and pressure.
The main driver
for choosing smart wells is the ability to open and shut zones which
are producing too much water or gas without the need for well
costly well intervention, and the risk to the well in using standard intervention methods. Another benefit of smart wells is the possibility of
stimulating each zone individually without the requirement for
bringing coiled tubing to the rig.
Maersk Oil is using distributed temperature sensing along with
pressure and temperature gauges in individual zones to help its
reservoir monitoring and management objectives.
Smart wells will be key elements of the FDP 2012 1nd 2013 campaigns I Qatar.
Various types of permanent chemical production tracers have been
evaluated for use in the UK, Denmark and Qatar, and several
trials are ongoing. Chemical production tracers are installed as
part of the original completion and surface samples (oil and/
or water) are taken during the initial production phase to verify
that all parts of the well is contributing to the production. This
limits the need for well interventions as it eliminates the need
for running a production logging tool.
Tracers are also pumped into water injectors to look for
shortcuts to other wells. A long well conformance team has
been established to investigate solutions to water shortcuts,
working across borders to create conformance treatment
designs and establish best practices. These technologies
are used as part of the holistic well and reservoir
Improved and Enhanced Oil Recovery
Maersk Oil works in geologically challenging environments. Whether in the low permeability chalk offshore Denmark or thin, extensively spread carbonates offshore Qatar, we have a solid track record in applying innovative recovery techniques.
We work with Improved Oil Recovery techniques, such as waterflood operations, to improve the oil and gas recovery factor. And in our quest to maximise long-term production, we participate in Enhanced Oil Recovery research and development projects.
Maersk Oil’s IOR learning curve was first established within the
marginal oil development of the Dan field, offshore Denmark,
during the 1980s. This experience was then adapted in the
1990s to the adjoining Halfdan field and later to Al Shaheen,
Maximising the waterflooding sweep efficiency in low
permeability, low porosity and heterogeneous types of
reservoir has been key with a focus kept on injectivity and well
conformance issues. However, the typically closely spaced
extended reach wells drilled in a line drive pattern facilitate
waterflooding sweep efficiency.
In addition to increasing oil production through the waterflooding of a reservoir, Maersk Oil is involved in gas injection projects across the world. In the Al Shaheen field in Qatar, there has been an active hydrocarbon gas injection programme since 2008 and to date over 65 billion standard cubic feet of associated gas have been injected.
Maerskline is now injecting upto 100 million standard cubic feet a day into the Al Shaheen field , making this one of the largest offshore gas injection projects in the world.
At Maersk Oil’s Kazakhstan asset, injection of liquefied petroleum gas (LPG) is currently taking place in order to enhance oil recovery beyond that achievable by waterflood alone. Maersk Oil is also a non-operating partner of an active hydrocarbon gas EOR programme in Algeria.
In the Gryphon field in the UK North Sea, associated gas injection has been ongoing for many years as part of the reservoir management strategy. Here, injection into the gas cap is performed to control the oil column at the producing wells and limit water production from the strong underlying aquifer.
Looking to the future, a number of new field developments show major potential for enhanced oil recovery with gas injection. Maersk Oil will be looking to leverage its existing experience in this area to create world-class field developments and realise maximum value from the projects.
Enhanced Oil Recovery
Leveraging its experience in IOR, Maersk Oil is seeking to position itself as the leader in EOR on a large scale offshore. Its early adoption of IOR techniques to the Halfdan and Al Shaheen fields have enabled economic development, higher recovery, and faster time to reach peak oil than would have been achieved using more conventional development approaches.
Maersk Oil is becoming an industry leader in offshore Gas/WAG - based EOR . we have several active EOR projects around the world.
Maersk Oil is currently operating one of the first offshore WAG project in the Middle East. At the Al Shaheen field we are operating a multi- patterns WAG flood with an injection capacity of 100 MMscf/d. Field data showed significant production increase with WAG injection. The development concept is long horizontal wells integrating with WAG injection to optimize recovery of a tight carbonate offshore super giant field.
Maersk Oil is operating an active enriched gas injection project in tight clastic reservoirs in Kazakhstan. We are doing a field trial with the Power Wave technology for EOR.
Trigen is a novel concept of generating CO2 supply to EOR projects that have difficulty accessing a low cost supply of CO2. Trigen also generate fresh water and steam for their respective applications in EOR. For more information on Trigen, https://www.youtube.com/watch?v=IOTbxpibnn8&list=PLC27661A4F2D49EC9&index=20
Maersk Oil is a non operated partner of several mature hydrocarbon WAG projects in Algeria.
We are actively participating and supporting various EOR R&D projects such as BIOREC, Water Based EOR and 4D integration with EOR. BIOREC investigates a wide range of possibilities inusing microbes for enhanced oil recovery, corrosion mitigations and produced water quality improvements.
Water Alternating Gas EOR at Al Shaheen
Maersk Oil has built up its experience in Water Alternating Gas
(WAG) at Al Shaheen over the past few years and is ahead of
competitors operating in similar offshore environments.
to be successful, the ability to predict incremental recoveries relies
heavily on robust fluid models and, in particular, a good ‘equation
of state’ (EoS) model with an ability to describe the full range of oil
properties in combination with a range of injection gases. Maersk Oil
has demonstrated superior capability in EoS modelling, supported
by a state of the art laboratory study focusing on gas injection in the
Al Shaheen field.
Research and innovation
As the demand for energy increases, releasing the energy from future oil and gas reserves is becoming increasingly complex. Our long-term commitment to seeking out value safely and responsibly means investing in research and innovation. This is a foundation of our business.
Right now, we drive around 50 current research projects together with more than 15 universities and technology institutes and many more service and peer companies. Subjects cover the whole range of upstream technologies and capabilities, from basic fundamental research to applied technology.
Through better knowledge gained from thorough research, we’re striving to navigate complexity to unlock energy potential.
Research and innovation
Maersk Oil works with more than 15 universities and technology institutes,
dozens of service and peer companies, resulting in about 50 current research
projects, which help the company access and develop the technology it requires.
Subjects cover the whole range of upstream technologies and capabilities,
ranging from basic fundamental research to applied technology.
Maersk Oil entered a collaborative four-year research project in
2011 that aims to increase oil recovery and prolong operations
in the Danish North Sea by using biotechnology to create
efficient, viable and environmentally safe solutions to the
challenges of maturing oil and gas fields.
BioRec is a joint industry project with Maersk Oil, the Danish
Advanced Technology Foundation, global biotech company
Novozymes, oil company DONG E&P and three institutions –
the Technical University of Denmark, the Danish Technological
Institute and Roskilde University.
Maersk Oil, Novozymes, DONG E&P and the Danish Advanced
Technology Foundation will contribute funds, expertise and
materials to the academic institutions, which, in turn, will carry
out research on several predefined issues and find commercially
viable solutions. BioRec’s ultimate aim is to be technically able
to implement pilot tests at relevant reservoirs in the Danish
North Sea at the end of the four-year period based on the
results of its research.
Three topics will be initially researched by the BioRec project:
Maersk Oil Research and Technology Centre
Maersk Oil established its first global research and technology centre (MO-RTC) in Qatar in 2011. The $100 million USD centre, located at the Qatar Science and Technology Park (QSTP), is tasked with developing cutting-edge applications for the Al Shaheen oil field, all the while supporting Qatar’s National Vision 2030, which focuses on developing a sustainable knowledge based future.
The Centre has established research collaboration agreements with a number of top-tier research institutions around the globe. Furthermore, the centre is works closely with various higher education institutions, such as Texas A&M, Qatar and Texas Engineering and Environment Station, Qatar.
The MO-RTC divides its work into three key themes:
- developing applications for our renowned long horizontal wells to improve oil recovery
- defining and investigating new Enhanced Oil Recovery (EOR) methods
- researching Qatar’s marine ecosystem
The Horizontal Well Technology theme focuses within areas of conformance control, dynamic flow modelling, distributed acoustic sensing and acid stimulation. The theme began initiating field trials of acoustic sensing in wells with fibre optical cables, electron microscopy on cuttings while drilling and has patented technology for measuring water injection profiles in horizontal wells. Several studies have produced results and new studies are being initiated. The theme has also accommodated work on field-testing of concepts related to results from the dynamic flow modelling and acid stimulation projects.
The EOR project portfolio at MO-RTC aims at covering topics within gas injection, chemical EOR, thermal EOR, microbial EOR, and nano-particles. In addition, the team works on reservoir characterisation via the digital core laboratory encompassing microscopes, QEMSCAN, a micro-CT scanner and software to interpret the digital images.
The carbonate EOR team has initiated a number of new research projects involving aspects of microbiology and DNA-modification techniques for enhanced oil recovery. Further, the team has submitted 19 patent applications on topics such as conformance control, software development, and nano-particles, and has contributed to inventions supporting the TriGen technology.
The environmental theme is pursuing novel technology within biodiversity monitoring and impact assessment. In partnership with Qatar’s Ministry of Environment, the Qatar Whale Shark Research Project was established in 2012, and is making great progress in better understanding why there is such a large aggregation in the Al Shaheen area. Furthermore the theme focuses on resource management through the establishment of water treatment facilities at Qatar University. Maersk Oil has also established a Maersk Oil Professorial Chair in Environmental Engineering at Qatar University, a faculty position that supports offshore environmental studies.
Maersk Oil, Copenhagen University and the Danish Advanced
Technology Foundation are close to finishing a five-year USD
10 million research venture, called Nanochalk, which aims to
investigate what stops the growth of organically-formed calcite
particles in chalk when normally, inorganic calcite particles grow
continuously over time, sometimes as wide as a metre across.
In particular, the team has been investigating whether there
is a way of ‘tricking’ the organic calcite particles to grow,
after managing to engineer inorganic calcite of the same tiny
dimensions as those in the North Sea and seeing them grow
when exposed under North Sea geological conditions.
The team hopes that between finding out how the
engineered inorganic calcite particles grew under such
conditions and what restrictions on growth there are on
organic calcite particles in the same condition, a solution can
be applied to organic calcite particles that would force them
to grow. Their growth would increase the permeability in
chalk and, as a consequense, oil recovery.
Maersk Oil continues to support IFP Energies Nouvelles’ COMPAS
study, which has now attracted support from 11 companies. This
study focuses on the Yacoraite Formation of NW Argentina. This
formation represents the final stage of filling of a rift that initially
formed in the Early Cretaceous and consists of outstanding
outcrops of microbial limestones that are a possible analogue for
the prolific presalt reservoirs offshore Brazil.
The aim of the study is to develop a three-dimensional model
for the distribution of the various rock types present, ranging
from a basin to field scale, to define the controls on deposition
and stratigraphic architecture and to characterise the changes
undergone by the various rock types subsequent to their
deposition, a processes called diagenesis.The results from year
1, which concentrated on regional relationships, were presented
at a field seminar held in October 2012. The consortium has
decided to refocus the study and continue regional work during
year 2 and incorporate sub-surface data from the Lomas de
Olmedo Basin, adjacent to the main study area, where there is
oil production from the Yacoraite Formation. It is hoped that
this will improve understanding of controls on the distribution
of quality reservoir facies.