EQUIPMENT AVAILABLE FOR AUTOMATING RIG OPERATIONS

April 16, 1990
Will L. McNair Texas Engineering Extension Service College Station, Tex. Several manufacturers are producing automated rig equipment, from complete systems to individual functions for existing drilling rigs. Significant improvements in well site time, costs of operations, and improved drilling performance have led drilling contractors to install this equipment on their rigs. This concluding installment of a two-part series details some of the equipment available for automating rigs.
Will L. McNair
Texas Engineering Extension Service


College Station, Tex.

Several manufacturers are producing automated rig equipment, from complete systems to individual functions for existing drilling rigs.

Significant improvements in well site time, costs of operations, and improved drilling performance have led drilling contractors to install this equipment on their rigs.

This concluding installment of a two-part series details some of the equipment available for automating rigs.

AUTOMATION APPROACHES

One of the major concerns of drilling contractors as they move toward automation is their current investment in rig equipment. Many have invested millions of dollars to obtain their current rig inventory and want to make the best use of that equipment without further investments.

The contractor also is faced with several issues that have developed from the industry's downturn. Among these are the trained rig personnel who left the industry for other occupations, competitors who have upgraded their rigs with new technology (such as top drives), and the inertia of maintaining the status quo of using existing methods and procedures to drill for oil and gas.

Two approaches can be taken by the drilling contractor if he decides to utilize automation technology. The first approach is to use his existing rig and make incremental changes toward rig automation, such as adding a top drive, then automatic pipe handling equipment, and so forth. This approach keeps his major investment intact while adding improvements that are attractive to the oil company operator.

The second approach is to purchase a completely automated rig that incorporates all of the features that provide the desired safety, performance, and reliability of operation. This rig would include a single console operated by one "rig-tech" and supported by one or two maintenance/support personnel.

It would include:

  • Automatic pipe-handling equipment, from the ground level to the makeup/breakout operations

  • Sensors to detect well and equipment conditions

  • Actuators to perform mechanical activity such as rotary drilling, mud pump operation, mud tank mixing, and cleaning operations

  • Safety controls to detect and shutdown systems in the event of H2S detection, gas kicks, or mechanical equipment failure.

A rig designed specifically with complete automation usually is more cost effective, smaller, lighter, and easier to operate than one with incremental modifications.

PERSONNEL

Implementing automation in drilling operations requires a review of the type of personnel required for operating the rig system.

Depending on the level of automation, the rig crew will still require an experienced driller who understands the techniques of hole construction, mud composition, downhole conditions, casing, and completion.

Also required is an individual with technical knowledge of the system's operation and equipment functions, and with the ability to both analyze problems associated with the system and maintain operations in the event of equipment failure.

Other support personnel may be required, depending on the size of the rig and whether or not it is land or offshore based.

The automation crew will have to be made up of experienced drilling personnel with the technical ability to handle operations and problems with electromechanical equipment.

Automation usually eliminates handling pipe or casing, makeup and breakout of connections, spinning chains, slips and tongs, derrickman and floorhand functions, and other operations that are considered dangerous.

Those operating the rig are located remotely from moving mechanical equipment and away from overhead equipment.

MAJOR DRILLING FUNCTIONS

By breaking the drilling rig operations down into job functions, we can analyze how the operator will perform the various jobs on the automated rig. Among these are:

  • Pipe handling from ground level to the rig floor

  • Making connections properly and torquing threaded joints

  • Controlling the drillstring with restraining slips

  • Lifting and lowering the drillstring

  • Turning the drillstring and bit for drilling and coring

  • Operating the mud system

  • Tripping out of the hole o Breaking out connections

  • Removing pipe in tripping-out operations

  • BOP operations and control

  • Casing and completion operations

  • Testing and logging operations

  • Rig up and rig down operations.

Many of these operations use the same equipment to perform the functions required and usually operate in synchronism with related equipment.

PIPE HANDLING

To utilize automation fully, the pipe should never be handled by rig personnel. The pipe should be unloaded onto a specially designed pipe rack that allows the individual units to roll into position one by one for processing into the derrick.

The horizontal pipe rack is typically slanted to roll the individual pipe into the remote controlled pipe-handling mechanism as shown in Fig. 1. After entering the pipe-handling mechanism, the pipe is moved into position above the existing drill string and automatically screwed and torqued with the equipment shown in Fig. 2 before being released.

During this operation of pipe makeup, the drillstring is automatically restrained in automatic slips on the drill floor. After the connection is made, the drillstring is slightly lifted, slips released, and drilling resumed with the rotary table or top drive under controlled conditions.

Tripping-out operations follow a similar pattern. The drillstring is restrained and held in the automatic slips, automatic wrenches unscrew the tool joint, and the pipehandling mechanism removes the pipe from the derrick and places it on the horizontal pipe rack for storage.

DRILLING

Automated drilling operations use several methods of control. First, the control of drill-bit speed is determined by electronic variable-speed dc or ac drives that can be adjusted to precise settings. On an automatic rig, the speed is programmed into the drilling program and automatically resumed after a connection is made.

In the event of drillstring harmonics or vibration at a specific speed, the speed can be automatically adjusted to stay away from these conditions.

Also controlled is the maximum torque that can be applied to the drillstring while turning the bit.

Second, bit weight can be controlled as well as penetration rate by controlling the amount of drillstring weight on the bit. Several systems have been designed to accomplish this, including the one by Parker Drilling Co. shown in Fig. 4 of Part 1 of this series (OGJ, Apr. 9, p. 49).

In the event mud motors are used in operations such as horizontal drilling, the motor speed and bit weight can be controlled with the use of feedback sensors and controls in the automatic system.

Pipe length-measuring techniques can determine the depth of the drill bit and compute the actual and average penetration rate over various intervals of drilling.

The method of turning the drill pipe can be selected between the traditional rotary table or the top drive. The top drive has proven itself in its ability to continue turning the bit while pulling off bottom and reducing the possibility of a stuck bit and subsequent fishing job. The top drive system is produced by several manufacturers.

An automatic rig operator's console is shown in Fig. 3.

TRIPPING

Automatic tripping-in of drill pipe is accomplished with the pipe-handling mechanism, automatic slips, top drive (if used), and automatic torque wrenches. After the pipe is positioned above the drillstring secured in the slips, the pipe is lowered until the threads come into contact with each other.

The top drive is used in most cases to provide the initial threading of the tool joint. Final torquing of the tool joint is accomplished with the automatic wrench assembly to the desired preset level.

After the connection is made, the pipe-handling mechanism is removed, the drillstring is lifted with the drawworks, and the slips are released. The drill pipe is then automatically lowered with the bit turning until the desired bit weight is achieved.

Tripping-out operation is essentially a reverse of the above description. The drawworks lifts the drill pipe out of the hole until the tool joint clears the slips.

The slips are actuated, and the pipe-handling mechanism moves into position to grasp the pipe section to be removed.

After the torque wrench unscrews the pipe, the top drive completes the separation and allows the pipe-handling mechanism to lay the pipe section down on the horizontal pipe rack.

All of these tripping operations are performed with the associated equipment moving in synchronism with one another for optimum time of operation.

MUD CONTROL

The mud system uses powdered barite and a liquid additive, which can be a chemical, oil, or water, depending upon the hole requirements. As the mud weight needs to be changed, the liquid additive will change the density and thus its weight. The process of mixing these components offers the opportunity to use an automatic batch mixing process to further automate the drilling operation.

Further automation can be achieved with the mud pump by automatically controlling its speed and thus mud volume flow rate. Downhole pressures can be monitored to ascertain the pressure required to be delivered by the mud pump and the required mud weight the system requires.

AUTOMATIC BOP CONTROLS

Protection of the hole, equipment, and personnel can be accomplished with hole sensors to detect gas and pressure conditions. If certain limits are reached that require rig shutdown an closure of the blowout preventers (BOP), and automatic BOP control system would work in conjunction with the operator's console.

In the past, manual closure of valves was required, but the same operation can be accomplished automatically with fail-safe electropneumatic or electrohydraulic valves. Manual override can be achieved as a backup to maintain confidence that the well will be controlled.

AVAILABLE SYSTEMS

Several manufacturers have developed automatic rig systems for the drilling industry.

The most advanced system is the W-N Apache rig that offers manual, remote control, or fully automatic operation. To date, 71 of these rigs have been produced and placed in operation over the past 15 years. A typical system is shown in Fig. 1.

The Apache rig is designed to operate with 2 or 3 personnel and has been manufactured for operation to approximately 6,000 ft. Rigs operating to 20,000 ft are available through an extension of its current design.

Automatic pipe-handling equipment is used to transfer single, 30-46 ft pipe joints to and from the rig floor. Automatic positioning, holding, and torquing devices are used for makeup and breakout of pipe connections during trips. The documented record of accidents relating to pipe handling and rig floor activities has been zero over the past 5 years.

According to Apache, the moving loads for the rig are reduced by one third due to its light weight and size, and it offers a 50% reduction in rig up/rig down time over conventional rigs of similar size. Spud-in can occur within 4 hr after equipment has been set in place at the rig site.

Apache indicates that connections of single pipe joints can be made up in approximately 1 min as compared to 4 min for conventional rigs. Complete round trips are comparable to conventional rigs at approximately 1,000 ft/hr.

The system is capable of handling small and large drill pipe of varying diameters as well as casing up to 26-in. diameter.

Routine drilling time is 1215% less than that of conventional rigs, and its cost of operations is 8-10% less, according to Apache.

It has been reported that a Japanese manufacturer has produced a completely automated rig that handles pipe up to triple joints. But it is heavier, larger, and more complex than the Apache system.

Varco Corp. has also made significant inroads into automating rig operations. It has elected to automate various segments of the rig, beginning with the top drive system.

Varco also offers automatic pipe-handling equipment (Fig. 4) as well as automatic torque wrenches used for making up and breaking out drill pipe. Varco's power slip and slip-style elevator are shown in Fig. 5.

Parker Drilling Corp., through its Partech Corp. subsidiary, has developed an automatic weight-on-bit control system (Parkomatic) as well as ungeared top drives for coring operations for its drilling subsidiaries.

BIBLIOGRAPHY

  1. Heagney, W.D., Crawford, Burt G., "Key to safety: People, not automation," Drilling Contractor, December 1989/January 1990, p. 43.

  2. W-N Apache Corp., Catalog No. 188, Equipment description and specifications.

  3. Varco Corp., Equipment Catalog, 1989.

  4. Parker Drilling Co., Equipment Catalog on Coring system, 1989.

Copyright 1990 Oil & Gas Journal. All Rights Reserved.