Is Extended Lateral Drilling Exceeding Current Completion Capabilities In Shale Plays?
The prolonged low price environment for oil and gas has increased the operator’s focus on employing cost saving methods anywhere practical throughout the drilling and completion process in shale plays. The business philosophy that ‘time is money’ certainly applies here and an evolution in operational efficiencies has begun to transpire.
The practice of drilling multiple wells from a single pad has cut flat time associated with rig moves and made fewer pads and mud pits necessary. Improved drilling efficiencies have also significantly cut the time required to drill to ‘kick off point’ in vertical sections by as much as 50 percent. And advances in bottom hole assemblies (BHA) and directional drilling capabilities have further allowed longer laterals to be drilled while staying ‘in zone’ within the formation.
Why Drill Longer Laterals?
Longer laterals are generally drilled as a means of maximizing productivity by increasing the length of formation contact with the wellbore. This allows for more stages to be perforated and stimulated which can contribute to additional production. Although longer laterals increase both the drilling and completion costs of the well, the overall economic impact has usually been a positive one.
The cost of the vertical wellbore section is capitalized regardless of the lateral length and incremental increases in production have tended to more than offset the extra cost of the extended lateral section. In many cases the estimated ultimate recovery (EUR) has been improved with extended laterals to a degree which encourages more operators to adopt this practice. The precise figures of the overall cost tend to remain confidential but the fact that longer laterals keep growing in popularity speaks to the fact that they have been deemed a profitable endeavor.
How Are Completions Affected in Extended Laterals?
Obviously the extra lateral length adds time and cost to completion operations. Current lateral lengths are reaching 10,000’ to 12,000’ and beyond. Some ‘super laterals’ are exceeding 15,000’. This trend of longer laterals is also creating technical challenges for completions in various ways:
Plug and Perf. (PnP) Completions.
The extended lateral length can exceed the limitations of coiled tubing to drill out plugs. As the lateral length is extended, friction between the coiled tubing and casing ID can become excessive and limit the ability to reach target depth. Even if coiled tubing can reach a composite plug the ability to generate the force required to effectively drill out the plug may not be available. Coiled tubing length limitations also apply to the ability to clean out sand after stimulation operations or to perforate the toe in extended reach laterals. Jointed pipe can be utilized in lieu of coiled tubing but can add time and expense to the completion operations.
Large bore plugs with steel mandrels are sometimes utilized when extended lateral lengths exceed coiled tubing capability. The plugs are designed to be left in the wellbore as opposed to being drilled out. However, if the steel plug presets in the wellbore before reaching depth it can be very time consuming if not impossible to remove the obstruction from the wellbore.
Ball Drop Systems.
Ball drop completions depend upon a series of graduated seat IDs to accommodate different size balls to activate sleeves at each stage interval. Eventually the seat ID becomes small enough to become a restriction to flow if left in the hole. The number of available ball and seat diameters is currently 40 to 50 sizes with the latest advancements, this represents an improvement over past limitations for the number of stages which could be deployed in a lateral. For designs where a seat can be retrieved or milled the coiled tubing length limitation will again become a factor.
Coiled Tubing Deployed Completions.
These completions utilize coiled tubing to shift sleeves or activate and release resettable plugs at each stage. Stimulation operations are performed while coiled tubing is in the hole. Obviously any limitations associated with the ability of coiled tubing to reach target depth adversely affects the application of this type of completion in longer laterals.
The Challenge That Lies Ahead
As the trend toward extended lateral lengths continues, the limitations of existing completion techniques may exceed the present technology’s capabilities and bring about all new mechanical risks to consider. The continued search for improved completion methods and technologies must be embraced in order to successfully accommodate these increasing lateral lengths. So far, the industry has been very innovative in responding to new technical challenges. And meeting this latest challenge will have very tangible applications for how the industry as a whole tackles shale plays.
No matter the nature of the projects that operators have in mind, Stage Completions strives to remain an innovator and pioneer in this arena as the industry continues to adopt these technologies as part of its best business practices.
About this Blog
In this blog, we hope to engage the oil and gas community with information about multistage fracturing. We think analyzing and offering our expertise about the ways our industry is evolving will help others seek the most innovative technologies and practices as they become available. If there’s a subject you’d like to know more about, please let us know. Thank you for joining us in the conversation.