Coiled tubing drilling
is an excellent example of how existing technology can help move the oil and
gas sector towards net zero.
The energy transition is something that
continues to dominate not just our sector, but much of wider society, too. It
has moved into everyday life and mainstream media and can influence political
and voting decisions. The COP28 conference has further pulled it into the
mainstream.
Although some of the headlines about the
hosts and the effectiveness of the agreements made at the conference were not
necessarily all positive, it did ensure that that the focus of the world was
very much on the sector and efforts being made to move it towards a greener
future. With businesses and governments around the world looking to ensure that
they and their supply chains are as green as possible, finding ways to use
existing technology to help that happen will be critical.
Coiled tubing drilling (CTD) can provide
the technology to allow many to move along the road towards net zero. It
provides a solution to gain access to key greener energy resources and provides
methods for safely storing them. It can elongate the lives of depleted wells
and provide controls that allow the safe management of often difficult to
control energy resources. It can achieve all of this with acceptable levels of
investment, especially when compared to locating and drilling new sites.
Why use coiled tubing drilling? The reasons for using CTD vary, depending on the application, but the
main reasons are: 1) thru-tubing or slimhole sidetracks; 2) underbalanced
drilling; 3) high-pressure wells that require specialist MPD/UBD; and 4) remote
operations. The most commonly used BHA diameter for CTD is 3 1/8-in., with
larger tools available with 5-in. OD and smaller tools available with 2 3/8-in.
OD. The BHA sizes are limited to 5-in. or below, due to the practical limits on
the size of coiled tubing. The technique is most suited to smaller hole sizes,
such as 8½-in. or below, with most wells drilled typically between 3 5/8-in.
and 4¾-in. The benefits usually stem from re-entry drilling or shallow gas and
oil wells. An alternative way to think about CTD is that it is a reservoir
drilling technology, so the closer to the reservoir, the more advantageous CTD
will be.
Producing, transporting and storing hydrocarbons
with less emissions. One of the key factors
in the energy transition is for the oil and gas sector to find ways to ensure
that hydrocarbons are produced, transported, stored and used as cleanly and
efficiently as possible. Many are looking at developing new waves of
technology to help with this process, but for new approaches to be adopted,
cost-efficiency is crucial for success and, more importantly, crucial for
sustainability of the effort.
Coiled tubing drilling’s contribution. Extracting the last drops from existing assets by re-entering and
drilling laterals in existing wells is a prudent and economically advantageous
strategy. This approach, rather than drilling a new well, does not mean that
you are getting less productive gains either; in fact, they are very
comparable. The key to success is to ensure the planning is accurate. The
following is an example planning process, based on a mature field when the
original reservoir has been depleted.
In this scenario, the operator may choose
to sidetrack, to access areas of virgin pressure away from the existing
wellbores or can access other productive formations that are behind pipe. The
formations between the casing exit and the reservoir need to be well-understood.
If there are particular zones that are troublesome, then now is the time to
assess whether the kickoff point can be lowered to avoid the zone, or if
operational controls will need to be in place in the drilling program.
The expected drilling fluids system should
also be assessed at this stage, as it defines the equipment requirements and
has a significant impact on the well budget (more on this later). This is also
the time to evaluate the completion requirements with a particular focus on
zonal isolation. For example, are there zones above that need to be isolated
from the reservoir and, if so, can they be isolated with a swellable packer or
is cementing required? Each consideration has a knock-on impact into the
suitability of using CTD in either a managed pressure or underbalanced set-up.
Once this initial planning is done,
ensuring that the existing wells are suitable for sidetracking is the next key
step. These wells need to be screened for integrity, current oil and gas production,
location, casing/tubing size, and ability to reach directional targets. Once
the initial list of wells has been created, then the available logs for each of
the donor wells should be reviewed.
Some older wells are situated on very small
pads, so the pad size for each well should also be considered, and permission
to extend needs to be sought, if required. A minimum pad size of 200 ft x 300 ft
is desirable, but there is some flexibility, depending on the equipment to be
used. In some cases, it may simply be that the pad has not been maintained to
its boundaries, but the rights are in place and, therefore, it just needs to be
prepared for the operation.
The casing and cement integrity are both
critical for successful operations. If a cement evaluation log is not
available, then it should be planned to be carried out well before the CTD
spread is to be mobilized, so that remedial cement jobs can be carried out if
required. Ideally, casing pressure tests should also be conducted at this time,
to verify the integrity of the casing where the exit will be. Once the donor
wells have been selected, the trajectories can be finalized, and the wells
permitted.
CTD reduces NPT/waste. So, with the right preparation, you are securing the same productive
gains as you would from a new well, and you also can quickly set up with
minimal waste. There is very little site prep needed. No mass transportation of
large amounts of new equipment is required, and so even at the first step, some
energy savings have been made. The use of CTD also has an impact on the work
environment, reducing noise levels, exhaust emissions and drilling waste.
Although these are relatively small contributions to the energy transition,
they are important and clearly show an advantage over the drilling of new
sites.
Cost. One of the
major barriers facing those moving toward net-zero is cost. The recycling of existing
technology to revitalize existing wells means that multiple immediate costs are
negated, helping companies to make an impact on the environment without having
to make a significant investment. CTD also has other economic advantages
that can encourage companies to move forward with such an environmentally
friendly approach. Advantages include:
Such economic factors can make a real
difference to decision-making, when it comes to the implementation of CTD. If
one can prove the prominence of environmental factors alongside financial ones,
there should be few barriers left.
CTD influencing cleaner energy. CTD can make a real difference in areas that are crucial for the use of
cleaner energy. CTD technology can be used for drilling wells for hydrogen (Fig.
1) and carbon capture storage (Fig. 2), both crucial elements in the
energy transition. The Royal Society released a report last year
that stated that unless the UK government kick-starts the construction of
large-scale hydrogen storage facilities immediately, it will not be able to
meet legally binding net zero targets by 2050. It also stated that although an
electricity system with significant wind and solar contributions offers the
lowest-cost electricity, it will be crucial to have large-scale energy stores
that can be accessed quickly, which will help to ensure energy security and
sovereignty.
All of this points to the hydrogen and
carbon capture storage wells being absolutely critical for a move towards
energy transition over the coming years. Utilizing existing technology, such as
CTD, will allow organizations to have wells ready for hydrogen and carbon
capture storage that will provide countries with cleaner energy options and,
importantly, a vital reserve securing their energy sovereignty.
Geothermal applications. Geothermal energy is being touted as one of the most advantageous
sources of energy. It is environmentally friendly, present in many areas, not
weather-dependent (unlike wind and wave), and can outperform even some of the
more conventional sources of energy in many aspects. Extracted from the earth
without having to burn fossil fuels means that geothermal energy is potentially
a key component for the journey towards net zero. The ability to create
electricity by having to rely on fossil fuels, does however, come with some
challenges.
The nature of the high temperatures needed
to produce electricity from geothermal sources makes this an incredibly
difficult and expensive task. Finding
new, deeper areas for geothermal sources adds to the technical and financial
implications. The deeper geothermal resources are often found in harder
geologic formations, certainly when compared to conventional hydrocarbon
reservoirs.
A substantial percentage of project costs
can be spent at the exploration and drilling stages, making it less easy to
justify. However, CTD can take the cost and risk away from the drilling of
geothermal wells, even at greater depths and more challenging geologic
formations. As CTD enables you to drill faster and bring the well on to
production in a shorter period of time, you are immediately reducing cost and
time to ROI.
One of the main issues associated with
geothermal drilling is lost circulation. This causes delays and drives up
drilling costs. Lost circulation sees a total or partial loss of drilling
fluids or cement in high-permeability zones, and natural or induced fractures. The
high temperatures associated with geothermal wells also create challenges for
maintaining drilling fluids. Despite lost circulation being widely studied and
discussed, it remains a barrier for some. However, again, CTD can help. As CTD
allows for easy control of pressures, it reduces the chances of lost
circulation, helping save time and money, making the establishment of
geothermal wells a realistic proposition.
Collaboration, not competition. CTD can help the energy transition in several ways, including sidetracking
from existing wells, without the need to drill for new resources. It can help
with the storage of carbon and hydrogen after capture, as well as producing
geothermal wells, negating many of the risks associated with this route to what
many consider the cleanest route to net zero.
However, the key to long-term success of
the energy transition is that the wheel does not need to be reinvented here.
CTD is just one proof point highlighting the fact that much of the needed tech
is already in existence within the sector. There does not need to be a
wholesale, mass, new investment to find cleaner tech to move towards net zero.
Instead, the industry needs to look at
existing technology, such as CTD, and “recycling,” utilizing the innovative
design to move towards net zero. Dismissing technology already used within the
oil and gas sector, because it is assumed it can only be used in relation to
fossil fuels, is naïve and will, frankly, slow down the journey to net zero. Not
taking into account existing technology, such as CTD, also makes it prohibitively
expensive for many to consider looking at options that include carbon capture
storage or geothermal wells.
Another factor that has to be taken into
account is if the energy transition is to be successful, then collaboration,
not competition, holds the key to progress. Groups that largely want the same
end result seem to be on opposite sides, instead of working together towards
net zero. They are pulling apart, making the journey longer, more expensive and
at worst, impossible.
There has to be acknowledgement that
moving towards net zero is a good thing for the planet. At the same time, a similar
acknowledgement needs to be made that if the world is to hit the carbon
reduction targets by 2050, then oil and gas will need to remain part of the
energy mix, just at 20% of their current levels. There can be no solution where
one approach is turned off and another turned on—overlap is critical, if the
energy transition is to be a success.
Through collaboration, accepting oil and
gas will remain a critical role in a net zero world. By ensuring that we look
at existing technology in the oil and gas sector to help with the transition,
there can be a real move towards a greener future. WO
Lead Photo: An underbalanced coiled tubing drilling project in North Dakota.
TONI MISZEWSKI is founder and managing director at AnTech Ltd, where he has led the company’s entry in the underbalanced coiled tubing drilling market. Before founding AnTech, he worked for Schlumberger, both in the field and in engineering development. Mr. Miszewski has a BSc (Hons.) degree in mechanical engineering from Imperial College, London, and holds several patents for downhole technology.