Adaptive technology
Digital integration
Improving production
Environmental performance
Ingenuity in progress
Insights: Restarting a closed-in solids producing well with a reservoir driven flow
Through the power of data analysis, and due to ongoing advancements in the field of offshore technology, it is now possible to restart a solids producing well with a reservoir driven flow and without the need for heavy intervention activity.

In our first insights piece, we outlined how Coiled Tubing (CT) has traditionally been used as a standard industry practice to resolve well intervention issues. Most recently, we highlighted how CT activity can align with the ongoing digitalisation journey of the sector, illustrating how this can be used to optimise the process and deliver enhanced results for operations. Now, in the final article of this series, we discuss the situations where a closed-in solids producing well can be restarted without the need for CT intervention and how this can take place.
Communication with the reservoir

Normally, when CT clean-out operations are undertaken, the coil provides the liquid flow required for solids removal. This means no flow from the well itself is used in the process. However, by verifying communications with the reservoir, it is possible to use a cyclonic desander and remove the need for coiled tubing entirely. This is because contact with the reservoir guarantees a reservoir-driven flow exists. With a reservoir driven flow, forces in the well can provide the required lifting rate to lift out the solids from the well and get it flowing again. While solids are lifted out of the wellbore, the removed solids are also managed in a safe manner topside by the desander.

Therefore, with the confirmed reservoir-driven flow, it’s possible to use a cyclonic desander in different rig-up scenarios, including a well-to test separator, a well-to-well rig up, or well to flow line, among others.
How to know if a reservoir-driven flow exists?

Verifying a communication with the reservoir means that there is an open passage from the wellhead to the reservoir. This is verified by wellhead pressure readings. From this, there are important factors to analyse and compare in order to determine if it’s possible to start a well without CT.

• The wellhead pressure highlights whether sufficient communication with the reservoir is in place to address the required clean-out operation.
• Confirmation that the well is only partly blocked
• The production rate and whether it is sufficient to transport the solids out of the well
Reservoir-driven flow separation in action

Once it is determined that a well is suitable to be restarted with a cyclonic desander, the process is straightforward.

1. A DualFlow desander is installed topside as close to the wellhead or flowline as possible. The system combines several data elements to measure solids production in real-time. The real-time data makes it possible to tune the wells for increased oil and gas production and, at the same time, ensuring produced solids are removed, measured and handled upstream of the process facility.

2. To start up the well, the choke is opened. The rig production choke is opened 100 % and a temporary choke is used to adjust the flow. This limits the wear and tear of the platform’s equipment. The temporary choke is normally installed after the desanding unit and is therefore not exposed to abnormal wear.

3. The accumulated solids in the wellbore are then produced safely by the reservoir driven flow out of the well. This is done by increasing the production rate to the lifting rate, or above, for the expected accumulated solids. The production rate is then increased when stable parameters are achieved.

4. The solids will travel topside, where the cyclone will separate them. The separated solids will then be flushed to a solids skip and no sand will be transported to the downstream process facilities.

5. Extraction and separation of solids continue until the whole wellbore is cleaned. The wellbore is clean once a decreasing trend of sand production is observed and the well is producing above the lifting rate for all potential solids.
Higher solids-free production
The real difference in the process using CT versus a cyclonic desander occurs at this next stage.

When a CT clean-out is performed it is only the wellbore itself that is cleaned. Meaning once the well is brought back into production there may still be particles that are loose in the reservoir. On the other hand, when cleaning the wellbore with reservoir driven flow and a desander, it also cleans the reservoir. This is important as the particles that become loose from the reservoir will get produced out of the well. This leads to a higher solids free production rate once production starts again after the clean out campaign.
The value case
CT is a heavy intervention activity, using lighter intervention activities such as a cyclonic desander to start a well can have a number of benefits:
The cyclonic desander requires fewer POB than traditional CT operations. Typically, there is a minimum of nine people on a CT operation, and maximum of four on a clean-out with a desander. A significant reduction in equipment also leads to a smaller and safer rig-up. As there is no risk of the solids entering the production facility, the use of a cyclonic desander also removes the need for manual handling activities related to emptying the production separator. This means HSE is improved.
Cost and increased revenue
A reduction in POB and equipment creates a much leaner planning and logistics process and results in significant cost savings. With decreased costs and guaranteed continuous production overall, field economics are improved. A key point to note is that during clean-out with a desander, the well is producing compared to CTCO where there is no production during clean-out.
Erosion and wear and tear
Erosion can have catastrophic impact on piping, equipment and instrumentation, with flowlines and temporary piping under threat. By choosing a cyclonic desander, such as the DualFlow 5K PSI, and by handling the solids as close to the wellhead as possible, it is also possible to protect the platform process facilities. Further, a cyclonic desander that has smart erosion software built in, makes it possible to monitor and predict erosion. By predicting when erosion takes place, it is possible to replace equipment before it becomes a problem.
Removing the heavy emissions associated with CT, decreasing POB and increasing safety will have a hugely positive impact on ESG metrics. By continuously using a desander on a sand producing well it is likely that the lifecycle of the well can be extended. This is because the solids are being continuously transported out of the reservoir and are not plugging it up, therefore the permeability of the reservoir is increased.