Oceaneering Develops Industry-First ROV-Based Approach to Complete Annular Abandonment

ROV multi-string hot tapping reduces risk and cost associated with annuli
venting and cement remediation

1 Project Overview

In 2021, Oceaneering was tasked by a major operator in Southeast Asia to develop an ROV-based solution to mitigate annular gas and avoid HSE risks in their wellhead severance campaign.

By leveraging extensive global experience and combining field proven technologies, a Western Australian based team designed, built, and operated an ROV-based annular access methodology based on multi-string hot tapping in a world-first operation. The operator was able to eliminate HSE risks, traditionally required jack-up rigs with specialized equipment, and the need to complete a saturation diving campaign.

Rov Vessel Spread Decommissioning

2 Challenge

The operator had more than 120 plugged exploration wells, in waters up to 85m depth, that required wellhead severance below mudline per decommissioning obligations.

A well survey discovered evidence of gas in the various annuli of 35 of the wells which would complicate severance and introduce additional HSE risk. Many of the wells had multiple annuli. The wellheads could not be safely severed until the annular gas was remediated by venting and cementing.

3 Our Solution

With a focus on safety and reducing risk, the operator requested that Oceaneering develop a vessel-based ROV multi-string hot tapping solution that could be used to gain controlled access to each annulus, remediate the gas, and inject cement.

This solution avoided the HSE risk of divers in the water and eliminated the need for a jack-up rig with specialized pressure control equipment.

Oceaneering’s two decades worth of experience in relieving annular pressure in multistring wellheads using our Pressure Annular Relief (PAR) Tool was foundational in developing this innovative, ROV-based approach.

4 Execution Plan

Oceaneering developed a suite of equipment for this industry-first approach in an expedited 20-week timeline, from initiation to project completion.

The project’s primary activity, including the design and manufacture of the majority of the suite’s hardware, was completed at Oceaneering’s state-of-the-art facilities in Perth, Australia. The Perth-based team was able to modify off-the-shelf hardware, use innovative design, and leverage positive vendor relationships to overcome pandemic-related supply chain challenges. Discrete items used to complete the suite were deployed from Oceaneering sites in the United Kingdom, Kuala Lumpur, Houston, and Angola. Once fully assembled in Perth, the hardware underwent a full testing program prior to being shipped to Thailand.

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5 Equipment

Wellhead Clamp with Hang-off Collar

Provided a secure mount onto the wellhead for the tooling. The hang-off collar prevented the vessel from being connected to the wellhead and set the drill height. It was removable, leaving the wellhead clamp in place, so wellhead connectors could be used.

PAR Tool

The tool is a CNC drill with force, torque, and position feedback used for drilling through the wellhead and cement to the next tubular as well as spot facing the target tubular. Precise control and sensitive feedback indicated if the tool was drilling through cement, steel, or water/gas. The tool did not rely on set distances and compensated and detected centralizer fins, eccentric casing, or joints.

Sealing Assembly

Connected to the wellhead clamp and pressed a sealing nose against the spot face made by the PAR Tool. The sealing assembly had a double block and bleed setup with API6D valves. The back of the sealing assembly included an Oceaneering® Grayloc® remote clamp for connection to the hot tap or a downline.

Hot Tap Machine

The machine was ROV-controlled and connected to the sealing assembly, forming a closed and pressure tested volume against the tubular. The drill extended through the sealing assembly and drilled a hole into the target annulus while maintaining a pressure barrier. The hot tap drill was removed by retracting the drill shaft and closing the valves on the sealing assembly.

Downline and Reeler with Mid-Line Breakaway

Provided the conduit from surface equipment, such as gas busters and cementing equipment, to the annulus via the sealing assembly. The mid-line breakaway was tethered to the wellhead with a dead-man cable and could close valves and break away in the event of a vessel run off, preventing uncontrolled release or damage to the equipment.

Contingency Plugs

In the event we were unable to get good injectivity on the well and unable to remediate the annulus, Oceaneering developed a set of plugs that could be installed by the Hot Tap Machine under pressure as a barrier until a workover rig could be scheduled to intervene.

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6 Results

Our ROV-based solution enabled the customer to avoid major HSE risks and benefit from a more cost and time efficient means of remediating annuli prior to wellhead severance. 

Oceaneering’s multi-string hot tapping suite remediated 14 wells over three months, requiring approximately 60% of the time and 40% of the day rate of a jack-up rig. This avoided additional risk and costs associated with both rig and saturation diving campaigns. 

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Company page Since our founding in the early 1960s, Oceaneering has expanded and grown globally to service several industries such as the offshore energy industry, defense, entertainment, material handling, aerospace, science, and renewable energy industries. In 1964, Mike Hughes and Johnny Johnson formed a Gulf of Mexico diving company called World Wide Divers. The company grew in response to increasing demand for their services and in 1969 merged with two other diving companies to form Oceaneering International, Inc. To solve the toughest challenges, we do things differently, creatively, and smarter. As your trusted partner, our unmatched experience and truly innovative portfolio of technologies and solutions give us the flexibility to adapt and evolve, regardless of market conditions. Our mission is to solve the unsolvable. We thrive by creating industry-changing technically creative solutions for the most complex operational challenges under water, on land, and in space. Our five core values establish a common culture and demonstrate what is most important for us as a company. Since the beginning, the company has transformed from a small regional diving company into a global provider of engineered products and services. Today, we develop products and services for use throughout the lifecycle of an offshore oilfield, from drilling to decommissioning. We operate the world's premier fleet of work class ROVs. Additionally, we are a leader in offshore oilfield maintenance services, umbilicals, subsea hardware, and tooling. We also serve the aerospace, defense, and theme park industries. Underpinning everything we do, safety is not only the foundation of our core values, but it is vital to our unmatched performance record and company culture. The industries we serve are as diverse as they are complex. Whether we are engineering deepwater umbilicals or developing robotics for aerospace applications, the safety and health of our employees, vendors, and customers is an integral part of our day-to-day business. If we are working, then our responsibility is to be working safely. Since our inception in 1964, we have placed a high value on employee safety—from diving services and subsea inspection to vessel-based installation operations. We have and will continue to evolve not only our health, safety, and environmental (HSE) processes, but those of the industries in which we work. Although we have been fatality-free since 1999, our HSE journey goes beyond statistics. As our portfolio of services has grown, we have continued to prioritize and advance our approach to HSE.