SURFACE DRILLING EQUIPMENT
While drilling rig equipment has not evolved as quickly as the PDC bit, it has undergone significant enhancements and, among the key areas described here, may have the most potential for increased efficiency in the future.
Directional and horizontal wells became significantly less difficult to drill, through the advent of alternating current (AC) drive drilling rigs, with joystick driller’s consoles and top drives; however, as horizontal wells are pushed further and further, operators must look at the pumping capabilities of each rig for every type of horizontal well that they drill.
For example, when horizontal shale wells were first developed, Louisiana state regulations were in place that generally limited wells to approximately 4,600 ft of lateral length and required the operator to stay within one section. This allowed drilling rigs with 5,000-psi pumping systems to effectively drill wells to 16,000 ft, MD. But as the industry has pushed to be more efficient in drilling laterals and developing reservoirs, the lateral lengths of horizontal wells have increased to 7,500 ft, and then stretched even more, to 10,000 ft.
The 5,000-psi pumping systems could not perform efficiently at new MDs of 19,000 ft to 21,000 ft, while having to drill and rely on extremely low hydraulic horsepower at the bit. Consequently, operators tasked drilling contractors with upgrading their pumping systems to 7,500 psi.
Today, pumping systems that can handle 7,500 psi are a standard request by many operators to drilling contractors. Operators will continue seeking rigs that can pump at even higher pressures, allowing drilling engineers to design for, and obtain, higher flowrates with more pressure drop across the bit. As a result, we’ll continue to see the ROP increase, thanks to continued innovation in this area.
DIRECTIONAL DRILLING TOOLS
Directional drillers cannot do their jobs effectively without directional survey tools and mud motors. And when these tools fail, the result is incredibly costly and time-consuming.
Adjustments in the way that a mud motor is set up, such as the number of power stages and the rotor stator fit, are necessary to match the hole conditions that will be encountered in the drilling of the lateral. Mud types, mud properties and knowing the maximum bottomhole temperature that the tools will be working in, are critical in properly setting up the directional drilling tools.
Because these tools are so crucial, industry has worked to improve them by enhancing rotor and stator materials, as well as by advancing the equipment’s design. The result has been increased performance of directional drilling tools, including, for example, a shorter bit-to-bend, and even-wall type mud motors that have allowed for greater torque output and better curve-building performance without sacrificing steerability or ROP.
We’re seeing better results, due to these enhanced tools, which have made it easier and faster to make more accurate curves. The process of building an angle is also becoming more predictable. In 2010, typical curves were drilled in approximately seven days. Fast-forward to today, and typical curves are being drilled in half the time, roughly three-and-a-half days. Personally, I have been able to drill the curve in as little as two days.
In the East Texas Haynesville shale area, specifically, I have observed improved results in drilling time for the curve and laterals through the use of larger-diameter directional drilling tools that are stiffer and allow for better control of curve building, Fig. 2.
And, as downhole mud motor performance improves, operators have been able to rotate the drill string more in the lateral section of the well, meaning a higher ROP in this section, and less time spent on sliding and making directional corrections.
PAD DRILLING
Because, by definition, horizontal wells require some directional drilling for every well, operators realized that drilling multiple wells from one general surface location would result in substantial cost- and time-savings. Thanks to pad drilling, operators no longer have to rig down, move the rig and rig back up between wells. By realizing these efficiencies, the time to move a drilling rig between wells can be cut by more than 75%, as compared to just four to five years ago, when moving from one well to another could easily require more than four days.
It has become a common practice in the industry today. Depending on the shale play, a drilling pad location may contain as many as six to 10 wells; at least three to four days per well can be saved by drilling them all on the same pad. Operators also should be taking advantage of the ability to have multiple frac crews on the pad location at one time, and being able to frac several wells at the same time, once the drilling rig moves off.
Additionally, now that walking packages are available for drilling rigs, walking from one well to the next, using the same mud system to drill and run casing on multiple wells, has become much easier, and the rig can move between wells in just a few hours.
This also allows the drilling rig to work backwards, drilling each production hole with the same mud system. This technique requires the operator to change out the mud system just once while drilling multiple wells on a pad.
An obvious downside to pad drilling is a large capital expenditure that is caused by drilling several wells from a pad before completion operations can begin. However, on several occasions, I have worked with multiple rigs on one pad, to speed up the completion process. This allowed for the drilling time to be cut in half, while drilling a total of six wells and being able to start the completion of the horizontal wells sooner.
ON THE HORIZON
While operators should evaluate each of these areas for cost- and time-savings, I believe that cutter and bit technology will remain the major factor in continued reduction of drilling costs, and surface drilling equipment improvements will follow closely behind in maximizing efficiencies. Additionally, wired drill pipe—which is already available—is just another example that could allow for faster detection of changes in hole conditions and tool wear or failure, which could help prevent stuck pipe and fishing operations.
The many new opportunities for greater efficiency in shale production not only show industry’s impressive evolution in recent years, but also indicate how much advancement is to come.
For operators, keeping up with the latest techniques and technologies that impact the bottom line can be the difference between success and failure. Through sharing of best practices and experimentation, they should proactively seek out and employ tools and techniques for increased efficiencies. Industry’s determination and ingenuity, paired with the rapid pace of technological advancements, can enable a successful path forward.
石油圈
