By Tim Marvel, SEF Energy
Downing, a leading technology provider, has developed an automated system that methodically eliminates the time between plug-and-perf stages with the goal of fracturing the reservoice 24 hours a day, seven days a week.
The ability to fracture a reservoir 24/7 is a monumental improvement over having to be on a frac site 24/7, which occurs today. Plug-and-perf stages start with pumping down a bridge plug on wireline with perforating guns to a given horizontal location near the toe of the well. Once the plug is set, the zone is perforated. The tools are then removed from the well, and the fracture stimulation treatment is pumped in.
In the implementation of an automation system, the primary barriers to fracturing the reservoir 24/7 are:
1. The time between stages (this includes transition time and pressure tests)
2. Downtime associated with gate valve maintenance and failures
Following an automation roadmap similar to those utilized for autonomous driving, Downing has automated multiple sub-systems over the past four years and integrated these sub-systems into a comprehensive automated surface system.
The elimination of these barriers provides wide-ranging benefits including 24/7 fracturing, cost reduction, safer operations, increased frac fleet utilization, logistical support and completion design flexibility.
Hydraulic Fracturing Automation Roadmap
Utilizing the roadmap developed for autonomous driving as a template, the company developed a hydraulic fracturing automation roadmap that has guided its development path to achieve its vision of fracturing the reservoir 24/7.
The automation levels describe specific stages in the development of a closed loop hydraulic surface system. Level 0 represents a completely manual process, with hydraulics introduced at Level 1. Level 2 adds functional automation, such as hydraulic latches or greasing manifolds. These functions are tied together into sub-systems in Level 3 as seen in automated frac valve, automated latch and automated zipper control. Level 4 automation digitally ties these surface sub-systems together enabling the sub-systems to work together without human intervention.
The roadmap culminates with a closed loop, Level 5 system that ties together the three primary frac systems: pump, wireline and surface systems. These systems function without human intervention, operating from stage-to-stage without human input except when required to stop the process for resupply or maintenance.
Current State of Plug-and-Perf Completions
Most plug and perf completions today employ Level 1 or Level 2 automation, which are relatively manual-operated process levels. At these current levels, hydraulic valve actuation is completed with levers, greasing is done manually, and wireline is attached via a latch.
Few, if any of these sub-systems are integrated, requiring human intervention using manual checklists to ensure proper function and sequencing. Functional time tracking is generally handled via spreadsheets with the start and stop time at the discretion of a company representative, leading to inaccuracies and inconsistency between frac jobs. Without consistent time stamping via automated algorithms, assessing the performance of one frac job versus another, as well as identifying improvement opportunities, is exceedingly difficult.
The hydraulic automation surface system roadmap provided the how to automate but not the why. As stated above, primary barriers exist to fracturing a reservoir 24/7. Each barrier involved significant human intervention, safety concerns and human-induced errors that no process could fully eliminate. Automation was the only way to completely eliminate each barrier and safety risk.
To understand the elimination of the barriers, we must first discuss the differences between human-driven workflows and automated workflows. Automation (and accompanying data) provides a path to continual, permanent improvement to frac workflows. As anomalies occur, data is analyzed, root causes identified, and workflow algorithms updated to fully eliminate the problem.
Human-driven workflows rely on training and process, both dependent on the individual’s adherence to the process and retention. Even with a highly trained workforce, personnel change and new training is constantly required and risk of operational failures rise. Automation eliminates an undue reliance on the competency of the individual.
Automation of Subsystems
To eliminate the first barrier – time between stages – a sub-system was developed that fundamentally changed how the transitions between wireline and frac were completed. With current industry practice, the well is shut-in with a gate valve, the frac stack above the gate valve is bled down to zero pressure, lubricator attached, filled, and equalized, and the entire stack pressure tested between every stage.
To achieve a simplified, repeatable workflow transition between wells, a completion system consists of the following integrated sub-systems providing full Level 4 automated control of the surface system without entering the red zone.
• FS Valve – enables entry of any tool into the pressurized wellbore with rapid equalization without closing in the well.
• FS Latch – enables attaching the lubricator without entering the red zone.
• FS iControl – controls all valves on location, en abling ability to continuously pump. Greases all valves during actuation.
• FS Ball Drop – allows dropping balls into the well bore without entering red zone.
• FS Control Center – self-contained operational center containing all supporting equipment.
The integrated system eliminates the time between stages with near instantaneous transitions from one stage to the next, enabling operators to continuously pump for the duration of the completion.
With the elimination of transition time and common issues between stages, the primary remaining barrier to fracking 24/7 was the ability to keep pumps online. Operational procedures and safety protocols prohibit personnel from entering the red zone while pumping, limiting the ability to exchange pumps during the frac. In addition, pumps do not have the operational life available to fully complete a frac job without repair.
The solution to this problem was to develop an automated system capable of shutting in a pump needing maintenance, replacing it with a new pump, and bringing the new pump back online. The objective was to achieve this while continuing to frac and without entering the red zone. With this barrier effectively eliminated, 24/7 fracturing is within reach.
The industry will experience significant efficiency gains with the advent of 24/7 fracturing. Assuming a current frac fleet average of 15-16 hours of fracturing per day over the course of a job, a new completion system enables up to a 50% increase (24 hours of fracturing) in efficiency, resulting in fewer days per well and faster online production for operators, higher pump utilization and revenue for frac companies, as well as safer operations and less emissions per well.
Benefits of Operational Efficiency
Completion engineers are focused on how best to drain the reservoir to maximize production at the lowest lifting cost. Unfortunately, surface system inefficiency can impact completion design as engineers have to balance the ideal design with operational considerations.
With the advent of continuous pumping, the operational switching cost between stages is negligible, giving engineers more design flexibility to consider various techniques. An operator may utilize additional, shorter stages or adopt the Kiel process.
Eliminating barriers to 24/7 fracturing significantly impacts the economics of completing wells. Analogous to the transition of tricones drill bits to PDCs in the early 2000’s driving drilling efficiency, large increases in completion efficiency will lower well costs and result in more wells completed per year. Frac companies will meaningfully expand the capacity of their fleets without expanding their asset base leading to higher revenue, profitability and returns on capital. Operations will become safer and more consistent, enabling better planning of resources. And without adding operational cost, automated completions will provide completion engineers the design flexibility to better drain the reservoirs, potentially leading to higher production per well.
Tim Marvel has 27 years of experience, primarily within the oil industry, serving in leadership roles related to drilling, completions, production, materials and subsea. For the past five years, he has led business development, marketing and technology for SEF Energy. Tim has a bachelor’s degree in Mechanical Engineering from Colorado School of Mines and is a licensed professional engineer.