NEW JACK UP DESIGN IMPROVES DRILLING EFFICIENCY

Paul C. Pedersen
Gregers Kudsk Maersk Drilling
Copenhagen

Finn Essendrop
Maersk Drilling
Houston

The use of mechanized processes and novel equipment on two new drilling rigs helps improve safety by removing workers from the most hazardous operations on a rig.

The rig design and layout increase efficiency by maximizing the time spent on drilling operations. New features on these rigs include a climate-controlled computerized driller's cabin and fully mechanized pipe handling.

One of the main goals in the design is to keep the crew out of dangerous and repetitive processes as much as possible. Much of the equipment monitoring, mud mixing, and pipe tripping takes place without direct crew involvement. Human intervention is for control purposes only.

Maersk Drilling used a systematic development process in the design of its two harsh environment jack up rigs under construction in Singapore. The two rigs are expected to be completed this autumn. Upon delivery, Maersk will mobilize the rigs to the North Sea where one will work for Elf Norway in the Froy field.

The systems analysis method of design borrowed technology from other industries, while conventional procedures were analyzed to help determine any equipment or operational inadequacies.

A conventional rig's equipment and the methods of operation leave much room for improvement. Yet, historically in the drilling contracting industry, the development of new equipment has progressed slowly. A reduction in the time during which the proper tools do not work efficiently in the well bore directly increases the rigs' productivity.

Drilling contractors must use their expertise to collaborate with equipment manufacturers in the development of mechanized and automated systems with a reliability comparable to that in other industrial systems. The development costs do not have to be prohibitive if a systematic approach is assumed, eliminating the need for massive modification during actual use. The focus should be on system relations and functions with extensive use of modeling and testing prior to release of the products for field use.

Operators must remain open to alternative methods and equipment. They must be prepared to differentiate between contractors on the basis of factors other than just the day rate. The higher unit cost for safer and more efficient equipment will reduce the total cost of a drilling program.

A change from the traditional day rate contract to a performance-related contract can allow a drilling contractor to demonstrate the quality of its equipment and crews with suitable rewards for superior performance. Thus, effective innovation can become proven with a minimum of risk for the operator.

A drilling contractor operates in a market in which the operator's success depends not only on the contractor but also on the operator's planning and execution of the well programs. The large number of third party contractors working on board a rig and often using the contractor's equipment complicates the scenario.

A contractor typically selects drilling equipment and procedures with direct involvement by the operator. A contractor must often promote new ideas to the operator before ideas can be proven with field tests. The short duration of typical drilling contracts complicates this process. Also, many operators may charter a rig during its life, and each operator may want different equipment according to its drilling policies.

Because drilling programs involve complex contracts, the operator often minimizes unknowns in the contract structure by selecting conventional equipment and methods rather than trying out new, and especially sophisticated, solutions with good potential. Thus, little incentive exists for a drilling contractor to invest in new drilling systems because the equipment and performance have generally had a minor role in the rig selection process. Rather, the economics of the flat day rate prevail.

DESIGN FOCUS

Basic rig design focuses on the development of the rig as an equipment platform. Contractors have typically invested in design improvements for operations in deeper water and harsher weather environments rather than in new drilling equipment.

The structures can be designed from established engineering principles and standards set internationally by classification societies and flag or shelf state legislation, often with little room for interpretation.

The competitive market for rigs has encouraged rig designers to change the engineering approach toward optimization of structural performance. Drilling contractors have risked large investments in improving rig structures because few alternatives have existed for the operator wishing to work under harsher conditions. Thus, a considerable difference has developed in the degree of sophistication between drilling systems and the structural platform.

Some operators now ask drilling contractors to assume a greater share of responsibility of drilling operations. The quality assurance systems accompanying this approach allow the contractor to document the efficiency of new equipment and techniques. An operator must substantiate any particular preference rather than justify it because "it has always been done that way."

State legislation and management vision within the oil companies have directed the operators' focus towards safety and environmental protection. Worker protection acts in most industrial nations, in particular the European Community, have set new standards based on other onshore industries. These standards necessitate changing traditional work routines on offshore rigs.

Many operators measure rig performance by personnel safety. Additionally, a contractor cannot attract the high quality of senior staff and rig management needed to run a modem drilling rig if they will face 10-15 years of hard, dirty, and potentially hazardous physical labor.

Rig jobs will move away from manual labor and into control and monitoring of mechanized and automated processes. The manual work will mainly involve maintenance.

SYSTEMS APPROACH

Today, little unnecessary work occurs on a well-managed drilling rig. Every activity has its justification proven from years of experience; thus, improving efficiency is not easy without the introduction of new equipment or new methods.

Studies of comparable onshore industrial systems indicate that some technology from other industries can be transferred to drilling rigs to avoid "reinventing the wheel."

Improving the drilling process in a systematic way requires a thorough understanding of all the processes and a focus on the purpose of an activity rather than on the equipment.

The act of drilling is considered a complex activity composed of a set of processes interrelated by purpose, sequence, and time. Each process comprises a subsystem with smaller elements and components. Many existing processes on a rig are repetitive, unchallenging, environmentally unsound, and potentially hazardous.

In most other industries, one or two of these characteristics alone can justify investment in mechanization or automation. Traditional methods for drilling equipment design, however, focus on changing subsystems and components mainly to reduce manufacturing cost. This type of development is product or manufacturer driven.

In contrast, equipment design on the system level involves a consistent analysis of the interrelation of various systems. The system approach is considered user-driven developments proactive method of increasing efficiency.

Daily drilling reports which list the time spent on various processes help establish a performance analysis for the initial rating of priorities on a rig. The list shows how the rig time is spent and thus which areas may justify an investment. Other important sources include near-miss and accident reports. One of the primary goals is to eliminate or minimize human risk exposure.

Reports from the planned maintenance system give excellent data about spare parts and time spent servicing or repairing machinery. Most important are the interviews with the crew members subject to the environment on a daily basis.

DRILLING SYSTEM

According to the drilling efficiency analysis and incident reports, the drilling system comprises six subsystems which require equal attention: drilling control system, drilling machine, pipe handling, blowout preventer (BOP) and handling system, mud supply, and mud return.

Consistent consideration of system efficiency and crew function in all these subsystems indicates that little would be gained from mechanical improvements without the use of highly skilled personnel with multifunctional training.

The drill floor activities were the most challenging to design. This area had the largest potential gain in efficiency and safety and the most reactionary attitudes to change.

Surveys of operators showed that the drilling system development would have to evolve from existing systems-the industry was not yet prepared for a design revolution.

Because certain potentially hazardous processes would remain, the design focused on reducing human intervention in areas with the highest risks or the most physical labor.

The drill floor subsystems include drilling control, drilling machine, and pipe handling.

Initially, these subsystems were analyzed for full automation, but this approach is impractical because human monitoring of certain phases is required. Thus, the personnel will control functions with a high degree of mechanization and not full automation.

DRILLING MACHINE

The initial focus for the drilling machine subsystem involved an analysis of the systems's functions: hoisting, rotating, and supporting pipe.

A derrick with a 40-ft square base and vertical sides to the racking board houses the pipe handling systems and Foxhole (trademark of the A.P. Moeller Group) work station in a proper layout. The derrick was designed to hold pipe on the setback during rig moves, thereby reducing unproductive time picking up and laying down pipe between well programs. The derrick is 160 ft tall and rated for 2 million lb. Table I lists some of the main dimensions and load figures for the rig design.

According to the drilling system analysis, a 3,000-hp draw works could allow the sandline and catheads to be separated from the hoisting system. The draw works uses hydraulic disc brakes which eliminate the need for a direct mechanical connection to the driller's brake handle. (This hookup allowed a new approach in driller's cabin design.)

The drilling system study clearly demonstrated that an in-line power source, or top drive, provides the most efficient rotation of the drill pipe. The redundancy previously obtained with a rotary table is achieved with two drilling motors on the top drive; the two motors also give a superior torque-speed ratio. Previous experience has demonstrated the high reliability of the top drive. The top drive is attached to a retractable dolly to improve tripping time.

Because of the time and risk involved in switching from top drive to kelly drilling with a crew not accustomed to this method and the improbability of having to make this change, the rotary table is used only to support the drillstring. A simple hydraulic motor installed in the table can rotate the string during connections.

The hydraulic and electric utilities have been separated from the drill floor and placed in two dedicated rooms above the draw works. This setup allows for proper maintenance in an environment without exposure to drilling mud and water.

The development of the drilling machine gives some work environment improvements, but its development is mainly focused on improvements in the rig's ability to make hole, with the availability of high torque and high rotational speed and the ability to run heavy casing strings.

MUD SUPPLY

The mud supply subsystems consist of preparation, storage, and pumping of the mud.

Historically, mud preparation has been hard, dirty, and potentially hazardous work with very little possibility for quality control. Accuracy in this area cuts mud costs and improves the performance of the drilling fluid.

The process of mixing dry bulk into a liquid base is well understood from other industries, which simplifies automation. Remotely operated supply lines and a controlled mixing process with a feedback loop for control parameters have removed human labor from the actual operation--the operator monitors the process from an air-conditioned control cabin.

This mixing subsystem was readily available with standard elements from other industries; no change in technology was needed.

Mud storage in enclosed pits with sonic level sensors minimizes human exposure to potentially hazardous mud environments. The storage and sensor equipment parallel standard ballast systems and other gauge applications.

The mud is supplied at 5,000 psi from three 2,000 hp pumps. This provides the pressure and flow rate to make full use of the high capacity top drive. To process large volumes of mud, the return system includes a 16-in. return line, two gumbo shakers, and four linear motion shakers for primary solids removal. The addition of centrifuges is a step towards reducing temporary equipment installations and making the contractor responsible for all services.

PIPE HANDLING

Pipe handling has the highest potential for human injuries on a rig. Thus, a mechanized system for transferring pipe from the cantilever pipe rack onto the drill floor, into the derrick, and into and out of the well improves safety for all concerned.

Because getting the pipe onto the drill floor requires some time, this function should be out of the critical path of operation. Furthermore, past experience has shown that if time is not pressing, the risk of making a bad connection with washout potential decreases dramatically.

Thus, it is advantageous to have a preparation function in parallel to the drilling function.

Maersk developed and installed the Foxhole system, which is used to make up or lay down drill pipe and drill collars without interruption of drilling. The Foxhole contains an hydraulic ram with a 20-ft stroke to raise or lower the pipe.

The other main elements in the system consist of an automatic pick up/lay down system (PLS) with articulated boom for transferring singles from the deck to and from the Foxhole and a pipe handling machine (PHM) with integral iron roughneck.

A typical work sequence for making up stands while drilling is as follows:

The PLS picks up a single from the pipe rack and delivers it to the Foxhole (Fig. 1).
The piston in the Foxhole lowers the single to align the tool joint at floor level.
The PLS picks up a second single from the pipe rack and delivers it over the Foxhole.
The PHM takes over and stabs the second single into the first and makes up the connection.
The piston hoists the double out of the Foxhole and the PHM holds it aside.
The PLS picks up a third single and places it into the Foxhole.
The PHM stabs the double into the third single and makes up the connection.
The piston hoists the finished triple from the Foxhole and the PHM moves the stand into the set back.

The ability to preassemble or lay down complete bottom hole assemblies or drillstrings in parallel with the drilling operation saves much time and allows for a smoother, less-hurried operation (Fig. 2). This improves efficiency and safety through a more structured approach to the whole drilling operation. The Foxhole can prepare many types of tools and bottom hole assemblies away from the work in the rotary.

Some of the major advantages of the Foxhole system include an increase in productivity, an improvement in safety by removing personnel from a hazardous operation, an improvement in the quality of work because rig hands will have more time to work carefully, and a reduction in tripping time (which enhances well control safety).

Other functions requiring human intervention include pipe doping, slips setting, and attaching the mud bucket. All these functions have been mechanized and are controlled from the driller's control room. Had these ancillary functions not been mechanized, the crew would still be needed on the rig floor despite the mechanized pipe handling.

BOP HANDLING

BOP handling on a jack up differs from that on a semisubmersible rig. The subsea BOP stack has many features that relate to the remote operation and the problems with repairs. Surface BOPs can adapt several of these features and thus reduce nipple up/down time.

A permanent lifting frame holds the unitized BOP (Fig. 3). Integral fixed work platforms allow easy access to rams and valves with fixed piping that allows vertical hookup to flex hoses. Control lines are gathered in a pod-type manifold to minimize hookup time and risk of mistakes. A camera in the BOP area keeps the driller informed about progress.

The next step in optimization is for the wellhead manufacturers to supply surface type wellheads with a profile for hydraulic connectors. These would allow hookup without hard manual labor.

DRILLING CONTROL

The subsystem with the most revolutionary change is the drilling controls. The development of the new drilling control room is a classic example of system development:

Field staff and industrial designers were involved in all phases of the project, with extensive modeling, CAD, mock up, and prototype before the final element was built.
There was a clear definition of target and evaluation criteria for different phases of the project, as shown by the Norwegian design prize awarded to the final system.
The rationale is that the driller is directly responsible for operator satisfaction and rig safety. Thus, he should have the best possible working conditions with instrumentation and controls to facilitate productive operation in a minimum stress environment.

The driller works next to the assistant driller who operates the pipe handling equipment--this work atmosphere facilitates good communication and common data presentation (Fig. 4).

LIVING QUARTERS

Recent legislation on operations in the North Sea has had a strong impact on the design of rig living quarters. The two new rigs have structural fire protection to H-120 classification around escape routes and control rooms. Next to the emergency control center, an assembly room was arranged with access along protected escape routes to lifeboats and helicopter deck. Sprinkler systems inside the accommodation and over the lifeboats provide additional fire protection.

The accommodation has been designed from modern principles of ergonomics. Recreation, sleeping, and working areas are separate, and the use of interior design, larger offices, and comfortable recreation areas creates a pleasant environment.

The central goal (through function analysis on productivity) is to improve the overall working conditions on board, mainly by keeping the crew stress-free as much as possible. The crew accommodations merely use elements from similar applications in other industries (e.g., hotels and ferries). This important change required little development work and little additional investment.

UTILITIES

The utility system was systematically broken down for the determination of the factors affecting performance.

Standard elements were studied for use in new applications.

One example is the use of a monitoring and control system for an unmanned engine room. Safety analyses showed that although areas with high noise and vibration levels could not be eliminated, the time spent in these areas must be minimized. Productivity analyses showed a need for engineers to be available for maintenance of drilling equipment and administration of the planned maintenance system.

These factors justified an automated control system, the basis of which came from the shipping industry. The control system required only minor modifications to fit the power consumption pattern on a drilling rig.

The systems approach ensured that other utility functions were developed so the advantage gained on one system (e.g., prime movers) was not lost because another required manual intervention (e.g., boiler system).

The utility function development involved some technical innovation with consideration for a work force of multiskilled personnel.

COMMISSIONING

Some operators are reluctant to employ a new rig directly from the building yard or to use new equipment. The attitude is based on the assumption that there is a greater likelihood of problems with equipment, operating systems, and crew. Given a comprehensive and effective quality control system throughout the design and fabrication, combined with experience in commissioning, new buildings and new equipment can have a smooth, incident-free start-up.

The quality assurance program must cover the entire construction cycle: preliminary concepts, detailed design, selection of the best available equipment and manufacturers, detailed supervision of the construction, stringent and fully documented commissioning and testing of each element in the system, and finally an extensive and rig-specific training program for the assigned crews.

TRAINING

A comprehensive program was established for crew training to effect a successful start-up.

In February, Maersk Drilling Training Center took delivery of a complete driller's cabin together with a 1:5 scale model of the pipe handling system, a fully functioning drilling control room in a 1:1 scale, an entire rig automation simulator, and a 20-user computer network for simulation of all computerized and automated control functions.

From May through December, approximately 100 rig crew members for the new rigs will train for 5-6 weeks at the center in areas covering rig structure, operation, and maintenance. Following training, the participants will be tested to ensure complete familiarity with all aspects of their duties. Additionally, the crew will spend several weeks on the building site to complete familiarization and training, including final commissioning of relevant equipment.

Such a training program makes the rig crew work effectively and safely from the first day of operations.

ACKNOWLEDGMENT

The authors would like to thank the A.P. Moeller Group for permission to publish this article.

BIBLIOGRAPHY

Pedersen, P.C., Kudsk, G., and Lund, T., "Drilling Contractors Long Overdue Focus on Drill Floor and Its Equipment," IADC/SPE paper 23863, presented at the IADC/SPE Annual Drilling Technology Conference, New Orleans, Feb. 18-21.
Lund, T., "Method and drilling rig for drilling a bore well," U.S. Patent No. 4850439, July 25, 1989.
McGill, J., "Integrated Driller Cabin," IADC/SPE paper 21924, presented at the IADC/SPE Annual Drilling Technology Conference, Amsterdam, Mar. 11-14, 1991.
Tjalve, E., "Systematisk Udformning at Industriprodukt."
Andreasen, Mogens Myrup og Tjalve, E., "Konstruktionsprocessens faser."
Maersk Drilling, "Newbuildings B222 and B223 - Executive Summary," internal document, May 6, 1991.