Operators are challenged with maintaining well integrity and service quality in an industry heavily affected by fluctuations in the market. Well integrity is concerned with the safe and reliable containment of all well fluids throughout the life of a well, including after decommissioning. In turn, service companies are constantly challenged by operators to provide safe and efficient ways of abandoning wells at a lower cost and in less time.

Historically, the deployment of mechanical plugs has been a standard and common way of securing wells for both temporary and permanent plugging and abandonment (P&A). In light of new solutions and methods that are being developed, mechanical plugs will continue to be a major contributor to P&A going forward. Requirements set for barrier plugs vary depending on local regulations and company-specific requirements.

Mandates such as ISO 14310 by the International Organization for Standardization (ISO) and API 11 D1 by the American Petroleum Institute (API) define well integrity and list requirements for design, documentation, testing and validation of plugs and packers in the market. In many cases, operators need solutions and equipment that at a minimum are approved according to these regulations.

Operators are searching beyond conventional solutions and require more technologically advanced tools and technologies that meet their expectations of cost and time savings without compromising the requirements for well integrity and service quality.

Conventional plug operations face limitations linked to conveyance and the options for downhole manipulation to operate a plug. Time spent tripping in and out of a wellbore is often the most time-consuming part of well suspension. Limitations related to plugs being deployed, such as tripping speed, circulation, weight requirements, torque and rotation, are often much more restrictive than what the rig equipment can handle and can be a limiting factor in an operation.

Plug technology advancements

Archer’s series of LOCK (V0-rated) and SPARTAN plugs have been optimized to deliver high performance and reliability, combatting harsh well conditions and resulting in cost efficiency and time savings. These plugs have been specially engineered to eliminate the need for weight to be hung off below to set as well as handle high tripping speeds, high circulation rates and minimum weight required above to set.

Developed to be simple and cost-effective, SPARTAN plugs offer the same benefits as the LOCK family of plugs. This type of plug, which meets the requirements of ISO 14310 (V3 to V6) certification, is designed for well suspension periods of days to months, ensuring easy deployment, a secure seal and safe removal on task completion. In other words, this plug is rapidly deployable, easy to set and easy to retrieve.

The company has further developed three new plug tools based on LOCK and SPARTAN plugs.

P&A casing retrieval plug system

The SPEARHEAD is applied where extensive hangoff weights or pull forces are required. With its heavy hangoff and pulling capability, the SPEARHEAD pulls the tieback or casing during the P&A of wells. It can therefore be used as an alternative to an original spear.

The SPEARHEAD also can be installed as an emergency hangoff together with a selective set valve that is installed below the plug. The ball valve, which is easy to operate, can check for gas in the drillpipe and annulus below before retrieving the plug. If necessary, mud can be bullheaded inside the drillpipe and then in the annulus by operating the selective set valve below the plug.

Case history

An operator in the North Sea recently planned a six-well P&A campaign. The original plan was to cut, pull and lay down more than 4,000 m (13,123 ft) of 7-in. tubing from each well. The operator intended to continue setting a bridge plug at 2,000 m (6,561 ft), then cut the 95⁄8-in. casing above the plug and finally displace the well to water-based mud. The process of retrieving and handling the tubing is time-consuming and costly. The operator asked for a plug that could avoid pulling the entire tubing string and save rig time.

Archer’s integrated P&A technology was to retrieve about 2,000 m of tubing and suspend permanently the remaining 2,000 m of tubing below the SPEARHEAD plug. When the plug and tubing were run in hole, a casing cutter was installed above the SPEARHEAD running tool. The SPEARHEAD, with the tubing below, was set at about 2,000 m and pressure- tested. The 95⁄8-in. casing was then cut above the plug, all of which was achieved in one run. The P&A operation continued with the retrieval of the 95⁄8-in. casing above the cut.

As a result, about 18 hours of operation time was saved for each well. The total saving for this operation was 54 hours for three wells as well as cost savings associated with rig time. The overall safety and risk profile of the operation also was reduced along with the time and costs associated with logistics, transport and handling.

Dual-plug system

The company’s VAULT is a dual-plug system that enables two plugs to be set and retrieved in one run, saving a considerable amount of time in a well operation. The company recently installed two barrier plugs and retrieved the wear bushing in the same run for a major operator in the North Sea. A standard TIMELOCK was used as the deep barrier plug, while the VAULT plug was installed as a shallow barrier. When both plugs were set and tested, the wear bushing was retrieved in the same run. To save even more hours of operational rig time, the two plugs can be retrieved in the same run. This can be achieved since the retrieving tool of the TIMELOCK plug is hanging off either just below or spaced out below the shallow VAULT plug.

Tandem plug system

The HUNTER plug system was developed with the goal of being run in combination with other tools and equipment such as wellbore cleaning equipment while having the ability to withstand high rotation and loads without the plug being set until activated.

The HUNTER plug allows the string to be rotated without unintentionally setting the plug. The ability to combine operations in the same run as setting the plug will save operators several hours of rig time.

Remote operations

Archer’s Integrated Operations center has played a part in delivering swifter and safer plug operations in the North Sea. It uses real-time data and new technology to enable cooperation between onshore support and offshore teams. Real-time data can be transferred over long distances, removing the physical barrier between expert onshore support teams and offshore execution. Integrated operation reduces offshore persons onboard, therefore ensuring smooth, flexible and cost-effective operations.