Reduced rig counts, lower oil prices and new rigs entering the offshore market are just a few of the issues drilling contractors are facing in 2015. As the offshore industry strives to minimize operating costs and maximize production, Archer’s modular drilling rigs (MDRs), the Emerald and Topaz, are an alternative to fixed drilling facilities. Utilization of an MDR in both greenfield and brownfield environments negates capex investments and/or costly reactivation projects. Rental of an MDR also eliminates operating, maintenance and recertification costs on existing drilling facilities at a time when cost reduction is essential.

Although the concept of MDRs is not new, environmental restrictions and platform limitations reduced the opportunities for successful deployment, particularly in harsh environment locations. However, as opex and capex costs continued to escalate, operators began looking for alternative solutions that could still deliver efficient operations at a more palatable cost. The company was convinced that adapting modular rig systems through the integration of modern technologies would address the limitations previously set.

“To address the challenges, our team had to approach this with a shift in mindset,” said Kenny Dey, managing director of Archer (U.K.). “Essentially, we had to prevent ourselves from falling back on the default design mode, which had been a factor of offshore platform drilling design and operation for more than 30 years.”

Key challenges included:

  • Reducing the size/weight of the existing modules;
  • Reducing or eliminating the large crews; and
  • Improving rigup time/operational efficiency.

By addressing these key challenges, a new type of offshore modular drilling unit that would become fully NORSOK D-001- and U.K.-compliant was built, allowing the units the ability to operate in the harshest environments in the world.

In developing the Emerald and Topaz MDRs, the company addressed the two largest challenges associated with offshore drilling: reducing costs and maximizing production.

Compact design

During the design process there was a specific emphasis on module weight, dimension and ergonomics, which would overcome the challenges faced with existing equipment.

In most cases, a drilling rig is based on a range III single joint running design; however, after extensive investigation, the company determined a singles rig reduced the overall package weight and footprint and overall well performance timing differences were minimal due to improvements in downhole equipment and technology advancements in recent years.

Because MDRs are built and then transported to offshore platforms, each module was designed for both road and sea transportation. Therefore, a lift weight of 12 mt per module was established. The weight limitation eliminated the need for costly heavy-lift vessels and enabled the majority of platform cranes to install the rig on location, typically only taking three weeks to build. As an option for locations with higher capacity cranes, individual modules can be connected together to reduce overall lifts. When compared to replacing a disused platform rig (along with the associated recertification issues) or hiring a jackup or mobile offshore drilling unit, the company’s MDRs are more cost-efficient when performing drilling and intervention tasks.

Improved automation

To eliminate or reduce the large crews associated with modular drilling units, increased mechanization and automation of rig systems has been integrated. The high degree of mechanization and automation in the MDRs has significantly reduced the size of the drilling crew and the construction costs. Pipehandling, make/break and drilling systems are all controlled from a central driller’s cabin rather than handled on the rig floor. Additionally, all major equipment has been integrated into a condition-based monitoring system, which can detect early signs of equipment failure and assists in optimizing maintenance routines.

Operational inefficiencies

By eliminating/reducing personnel on board, Archer was able to deliver a flexible solution and reduce operational inefficiencies. MDRs such as the Archer Emerald and Topaz offer drilling services, rig-assist services, through-tubing rotary drilling, workover services, complex completions, casing-while-drilling and more.

Case studies

In 2012, Archer’s debut MDR, the Emerald, began operations off New Zealand. As the company’s first super singles rack-and-pinion MDR, the Emerald combined a proven alternative method of conveyance with the latest in drilling technologies all housed in a lightweight, compact modular package. Its multipurpose design makes it equally capable of undertaking drilling, workover, and plug-and-abandonment operations. This operational flexibility, along with the cost efficiencies it offers compared to alternative offshore drilling facilities, has made it an attractive option for operators, especially at a time when production optimization is at its peak.

“Archer’s redesign of traditional modular drilling rigs really paid off,” Dey said.

The Emerald has risen to the challenge of addressing customer concerns. The rig recently completed a series of wells in a client’s drilling program, with the second well drilling to a depth in excess of 6 km (20,000 ft).

The third well was completed eight days ahead of schedule and has delivered a global top quarter performance against all other worldwide platform drilling operations for the client. The fourth and final well in the series was completed 30 days ahead of customer expectations, saving significant time and money.

To date, Emerald is seen as a breakthrough in its field and, as a result, has led to the creation of a second MDR, the Archer Topaz. Built in accordance with the NORSOK D-001 Drilling Facilities Standard, the two MDRs operate in the harshest environments in the world.

Future plans

The Archer Emerald has officially wrapped up a very successful first campaign in New Zealand. It now has been demobilized and is on its way back to the U.K. for a period of modification, inspection and five-year reclassification.

The Archer Topaz was deployed to Norway ahead of schedule and has been successfully installed and commissioned on Statoil’s Heimdal platform. This follows a contract win for Archer with Statoil in February 2013 for the permanent plugging and abandonment of 12 gas wells on the Heimdal Field in the Norwegian North Sea.

Carrying out plugging and abandonment operations on a modular rig will be a first for Archer and for the industry as a whole. Looking to the future, the company plans to expand and diversify its fleet capability.