Increasing efficiency, safety through automation on land drilling rigs

Today’s land drilling activity for oil and gas E&P requires dramatic improvements in the automation field in order to enhance performance and efficiency and lift up safety standards. Game-changing incidents like Macondo have left an inheritance of stricter rules on safety protocols and certifications. Recovering the subsequent cost increase for compliance and liability risk is a massive challenge.

FIGURE 1. Special characteristics of the HH rig design (left) make its shape far different than that of a conventional 2,000-hp rig. The top drive has an automatic pipehandler, which rotates inside vertical pipe racking that surrounds the rig floor. (Images courtesy of Drillmec Drilling Technologies)

The design and technology of land drilling rigs has remained conservative and traditional for too long. In comparison, downhole tools and well drilling technologies have undergone significant changes that require innovative approaches toward the design and components of drilling rigs.

For a few years many new technologies, including ones drawn from offshore rigs, have been applied to new land rig designs. Some of the new rigs are already fairly well known in the industry worldwide. The results seem to indicate that the efficiency is related to an extended use of automation, mostly applied to those actions that are repetitive, such as tripping the drill-string in and out.

The HH Advanced Series rig is a type of hydraulic land drilling rig that allows safe working conditions for the crew, leaves a small environmental footprint, and has a high level of operational efficiency. The special characteristics of the design make its shape far different in comparison than that of a conventional rig (Figure 1).

The hydraulic equipment is integrated in a largely automated drilling process, and all of the drilling functions are centrally controlled by a top-of-the-line driller’s cabin. The hydraulic rigs range from 150,000 lbs to 600,000 lbs of static hookload capacity, which translates into a drilling capacity of wells up to 4,573 m (15,000 ft) in depth, depending on the well design and its casing profile. This covers more than 80% of all oil and gas or geothermal wells drilled on land worldwide. The rig is integrated into a trailer that does not need to be disassembled when moved. It is self-erecting by means of dedicated hydraulic pistons.

Automation reduces crew needs

An advanced automation concept allows most of the routine drilling operations to be performed, including tripping in and out the drillstring and tubulars, with an almost unmanned rig floor where the worker’s presence is basically limited to thread doping and bottom-hole assembly handling. Therefore, a smaller-than-usual crew is needed to operate the rig, resulting in an increase in safety for the working conditions on the rig floor. It is hands-off work since nobody is exposed to direct contact with rotating tubulars, tongs, and wrenches or falling objects.

The most noticeable characteristic of the HH rig is the self-erecting hydraulic telescoping mast with reduced height. The hydraulic cylinder is the main hoisting element of the rig and has an integrated hydraulic top-drive built in it. There is no derrickman, and no monkey board is needed. Therefore, these rigs do not have the conventional mast structure, nor drawworks, long wires, or traveling equipment.

FIGURE 2. The length of time of each repetitive activity becomes regular, predictable, and shorter improves the performance of the hydraulic rig.

After the rig is raised to the required substructure level, the mast is raised to its vertical position by two hydraulic pistons. This puts the top drive in working position. The top drive is equipped with a torque wrench, and it has a horizontal displacement capability that allows it to move pipe from the center hole to the mousehole and vice versa. The top drive has an automatic pipe handler, which rotates inside a unique vertical pipe racking that surrounds the rig floor. The pipe racking is made of a number of mobile bins, and the number varies with the size and type of rig.

The arms of the pipe handler are installed on a vertical rotating tower. These have two clamps that take the drillpipe from any container of the vertical pipe rack and transfer the pipe to the mousehole or vice versa, depending on an electronically preset order.

The system works automatically in a programmed logic-controlled sequence, but the driller retains the capability of driving the full system from his chair in the doghouse through the controls and touchscreens installed on the drilling console. A hydraulic power tong and automatic slips also are integrated with the rig.

The hydraulic power tong is another element that allows unmanned rig floor activity. The power tong is stored in the back of the fixed part of the mast base. It is adjustable in height and driven from the drilling console, rotating back and forth from the center hole to break or make up connections with no need of manual intervention.

The overall dimensions of the HH rigs are much smaller than conventional rigs with corresponding power, thus making the rigs more cost-efficient from a transportation aspect. All of the major rig modules are permanently mounted on semitrailers and are self-erecting for fast and safe transport between locations. A smaller number of loads are needed compared to a conventional rig of equivalent capacity.

The drilling parameters can be controlled during operations by the hydraulic top drive, which allows automatic drilling with a constant weight on bit or rpm selected by the driller on the control panel. Predetermined values of over-pull also can be set. Such features, coupled with the back-reaming allowed by the top drive while tripping out, considerably reduce the risk of stuckpipe.

Smaller drilling crew, no accidents

The features of the HH design favor efficiency for the reduced drilling crew and a considerably smaller number of accidents, which is in direct correlation with the safety measures of the different drilling processes and the actual number of people involved in the operation.

Accidents often happen while tripping strings on a conventional rig, where there are many people doing heavy manual work in the fairly restricted space of a drill floor. On an HH rig, with a smaller crew and most of the routine activities automated or remotely controlled, the possibility of casualties is reduced. The possibility of being hurt by falling objects is basically nonexistent because there is no crew present or activity above the rig floor, and the hoisting action is carried out through the telescopic movement of the hydraulic mast instead of drawworks.

The small number of recorded accidents demonstrates that activity on these rigs is done with the highest possible level of safety for the entire crew. The length of time of each repetitive activity becomes regular, predictable, and shorter, mostly because it is not affected or conditioned by human behavior (Figure 2).

It can be further enhanced to reach full automation and to cancel almost entirely the manual work on the rig floor. This seems the right way to finally reach zero accidents in the land drilling industry. This will contribute to lowering the overall cost of oil and gas E&P activity.