Injection Wells & Commissioning

Explore each method in depth - benefits, limitations, plant and quality control on its own page.

Injection Wells & Commissioning: step by step

1. 1

   Step 1: Confirm the store and build the containment case

   Long before any drilling, the subsurface team characterises the store: the formation that will hold the CO2, the seal above it, the structure, the pressure regime and how the injected fluid is expected to move over time. Seismic data, any existing well data and dynamic modelling all feed a case that the store will contain what is put into it. Critically, that work also identifies every legacy well within reach of the store, because an old borehole through the seal is the most likely leak path there is, and its construction, abandonment and condition all have to be assessed. The regulator reviews the whole case before a storage permit is granted, and the permit sets out what has to be monitored, reported and demonstrated. Construction cannot begin without it, and the case continues to be updated with real data for the life of the site.

2. 2

   Step 2: Mobilise and prepare the wellsite

   Onshore, the wellsite is built as a self-contained pad with the containment, drainage, hardstanding and access a drilling rig needs, plus the environmental controls the consent requires. Offshore, a rig or a vessel is mobilised, a site survey confirms the seabed is clear of hazards and obstructions, and the operation is planned around weather windows and vessel availability booked long in advance. Either way, the preparation is heavy on logistics: the drilling campaign consumes materials, people and support continuously, and running out of anything mid-operation is expensive and occasionally unsafe. Emergency arrangements, well control equipment and the competence of the crews are established before the rig starts rather than during. This is a phase where the operator's systems govern and the construction contractor is a guest.

3. 3

   Step 3: Drill and case the well

   The well is drilled in stages, with each section lined with steel casing and the annulus behind it cemented before the next section is drilled. That arrangement of casing and cement is the barrier system, and it is the product being bought - it is what stops the injected stream going anywhere other than the target formation. The design of it comes from the well engineer and is reviewed and accepted by the regulator, and materials are chosen for a service life measured in decades in the presence of the fluid the well will carry. Each stage is logged, measured and evaluated as it is completed, and the quality of the cement behind the casing is assessed rather than assumed, because a poor cement job is a leak path that is very difficult to fix later. Deviations from plan are recorded and their implications reassessed before drilling continues.

4. 4

   Step 4: Complete the well for injection service

   Completion turns a cased hole into a working injection well. The tubing that the stream will flow down is run in, along with the packers, valves and safety devices that form the inner barriers, and the connection to the target formation is established in the way the design specifies. Downhole gauges and any permanent monitoring equipment go in at this stage, because retrofitting them later means intervening in a live well. Materials throughout are selected for compatibility with the stream over the long term, on the assumption that the well will be in service far longer than most industrial equipment. Once complete, the barrier arrangement is tested and its condition recorded as the baseline for the well's integrity management, which will be revisited at intervals for as long as the store is in use.

5. 5

   Step 5: Install the wellhead, arrival facilities and control system

   At surface, or on the seabed, the wellhead and its valve arrangement are installed and connected to the facilities that receive the stream from the pipeline. That includes the arrival and metering point where custody passes, the control valves that regulate injection, the heating or conditioning equipment the design requires, the safety and shutdown systems, and the venting and relief arrangements. Subsea developments add umbilicals, control modules and the remote control link back to shore. All of it is installed, connected, tested and functionally proved. The safety systems are treated as the priority: shutdown functions, isolation arrangements and detection are individually demonstrated, and the interfaces between the well systems, the pipeline operator's systems and any host facility are agreed and tested with everyone present rather than assumed to align.

6. 6

   Step 6: Take the baseline before anything is injected

   Before the first injection, the site is surveyed comprehensively so that there is something to compare against later. That means subsurface surveys of the store and the overburden, measurements of pressure and conditions in the formation, sampling of groundwater or seabed conditions as relevant, and characterisation of the natural background - because CO2 occurs naturally and a monitoring system that cannot distinguish natural variation from a leak is not a monitoring system. Well integrity baselines are recorded for every well, including any legacy wells being monitored. The monitoring plan the regulator approved defines what is measured, how often and to what accuracy. This is the last moment the site exists in an undisturbed state, and every claim about containment made over the following decades will be measured against what is recorded now.

7. 7

   Step 7: Commission the chain and start controlled injection

   Commissioning here is a whole-chain exercise. The capture plant, compression, pipeline and wells are each complete, and the task is to prove they work as one system across boundaries that different organisations own. The pipeline is filled and brought up in a controlled way, the stream quality is verified at the metering point against the entry specification, and injection begins at a deliberately restrained rate. Everything is watched: well behaviour, formation response, pressures, temperatures, metering and the monitoring systems. Injection is stepped up gradually as the store demonstrates it is behaving the way the model predicted, and the operating envelope is confirmed against reality rather than against the assumptions used to design it. Trips, shutdowns and emergency responses are proved deliberately. Where the store behaves differently from the model, the model and the operating plan are revised.

8. 8

   Step 8: Hand over into an obligation, not out of one

   The construction contractor hands over an asset, but the operator is not receiving a finished job. Storage is a long-duration commitment: continuous monitoring of the store and the wells, periodic surveys to track where the CO2 has gone, regular well integrity checks, reporting to the regulator against the approved plan, and a corrective measures plan that has to be ready to use if something is not as expected. Injection may run for decades, and after it stops the site has to be monitored until it can be shown to be stable and behaving predictably, at which point responsibility may transfer to the state under the terms the permit sets out. Practically, that means the handover documentation has a much longer half-life than on a normal project - the as-builts, the well records, the baseline surveys and the commissioning data are working documents for the rest of the century.

How long does Injection Wells & Commissioning take?

Typical duration: Drilling and completing a well is measured in weeks to months each; site characterisation and permitting run for years beforehand; whole-chain commissioning and ramp-up take months; and the monitoring obligation continues for decades after injection stops..

Related processes

• Site Civils & Heavy Foundations
• Capture Plant Installation
• Compression & Conditioning
• CO2 Transport Pipelines
• New purpose-drilled injection well - method
• Re-used or re-completed legacy well - method
• Monitoring and observation wells - method
• Subsea versus platform or onshore wellhead - method
• Carbon Capture & Storage (CCUS) sector guide
• Utilities & Energy - group of sectors