Systematic Coiled-Tubing-Efficiency Improvement Reduces Operational Time

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Deepwater coiled-tubing (CT) well interventions can benefit from significant rig-time reduction and cost savings associated with improved efficiencies of surface processes. Efficiency improvement requires a systematic approach and detailed analysis of each part of the process. The efficiency methodology allows for systematic improvement in all areas of CT operations, specifically for surface activities. The total efficiency solution described in this paper requires no additional cost to service providers, and results can be seen immediately.

Deepwater Coiled Tubing

The use of CT for well intervention can provide many downhole solutions throughout the life of a well. Although there is much discussion of the financial and technical aspects of CT in the industry, less conversation is directed toward the efficiency of CT surface processes.

The expansion of analysis, specifically to CT process efficiency both before and after in-hole operations, is necessary for a holistic approach to total efficiency improvement. The stages of CT operation shown in green in Fig. 1 can be identified as five distinct surface activities.

Fig. 1—Key deepwater CT stages.


Design Methodology

The first stage of the efficiency solution involved analysis of past performance. Some limited performance data were collected and reviewed, primarily on CT rig up, pressure testing, and transition time between CT and wire services (wireline and slickline).

The underlying strategies of several widely accepted continuous-­improvement programs, such as lean principles and the define/measure/analyze/implement/control methodology, were used to provide the link between performance and improvement.

Low-performance areas and areas of recurring nonproductive time (NPT) were addressed through root-cause analy­sis and remedial-work plans that were focused on specific tasks. Meanwhile, high-performance areas were analyzed to document the best practices for efficient operational execution so that efficiency gains could be realized for the duration of the campaign.

Performance is compared with both baseline and previous-operation performance data so that trends and inconsistencies could be identified easily.

Equipment Mobilization/Demobilization and Lifting

The first stage of any CT operation involves mobilizing the required equipment to location. A typical CT spread may require 30 to 45 individual lifts to move equipment from the workboat to the rig. This first process, termed boat work and equipment spotting, is most commonly tracked by total time required to place the entire CT spread on deck.

Areas of Improvement. Allocation of Personnel. Proper personnel allocation allows for the correct number of personnel to concentrate on a required task. Allocating too few personnel for complex lifts or allocating too many personnel for standard lifts introduces waste into the process. Proper personnel allocation addresses both wasteful cases—oversupply and undersupply of personnel—to ensure efficient process completion.

Defined Work Plan. Inefficiencies during the equipment-spotting process occur when the lift sequence and ­equipment-placement processes are handled without clear direction. A documented work plan, with both lift sequence and equipment destination, is critical for efficient completion of equipment spotting.

Work Site Preparation. At a minimum, the work site must be prepared for a CT intervention before the equipment arrives on location. Temporary equipment, tote tanks, and other miscellaneous items in the planned CT-­equipment-spotting and rig-up areas should be removed. Additionally, any support activities, such as erecting scaffolding, preparing the well bay, and installing barriers, may be performed in advance.

Crane Operations and Availability. Perhaps the largest bottleneck during the equipment-spotting process is crane operations and availability. Being a shared resource on location, the crane must be prioritized to ensure necessary activities are progressed. Perceiving the crane as a temporary resource ensures optimization of use while also ensuring that the process-work-flow design accounts for periods of crane unavailability.

Rig Up and Rig Down

Stages 2 and 5 of a deepwater CT operation involve CT rig up and rig down. While clearly inverse processes, rig up and rig down exhibit a multitude of similar characteristics. The ultimate objectives of both processes are opposing, but the nature of the work to reach the goal is nearly identical. Each additional item rigged up must later be rigged down, whereas efficiency gains experienced during rig up most likely will be exploited during rig down. This doubles the reward for optimal work flow and efficient design.

Understanding the process work flow of a rig-up or rig-down series is imperative for process improvement. Rig up and rig down involve significant time working at heights. Activities performed while working at heights must be reduced. In fact, working at heights is the largest bottleneck of all surface activities. Nearly every prolonged rig-up process can be traced back to undesirable performance while working at heights.

Areas of Improvement. Upon applying the systematic efficiency method to rig up and rig down, the following improvement opportunities were identified.

Bottleneck Aversion. Bottleneck aversion involves recognizing and reducing the number of tasks that may cause congestion. Eliminating at-height tasks altogether can have a profound effect on efficiency improvement. As previously mentioned, any task eliminated during rig up will also be eliminated during rig down.

Standardization. In both design and execution, standardization can guarantee consistent, efficient improvement. It should include, as a minimum, pressure-control-stack configuration, low- and high-pressure-line configuration, standard work instructions, and operational checklists.

Work-Flow Management. Work-flow management ensures that tasks are completed in the most efficient manner to complete a total process. Additionally, work-flow management involves strategically allocating the proper amount of personnel resources for each task.

Multiskilling of Personnel. Specifically, multiskilling is perhaps the pinnacle of efficiency. From a work-flow perspective, consistency and continuity are realized across all performed services because multiskilled personnel perform a variety of tasks. Naturally, cross-trained crews allow the work involving multiple services to occur faster because the defined work plan takes into account the required tasks.

Purpose-Built Equipment. Purpose-built equipment must be reserved for opportunities to eliminate tasks or to dramatically improve the efficiency of certain tasks. Generally, specialized equipment is developed to alter significantly the method in which a certain task is completed.

Pressure Testing

Stage 3 of a deepwater CT operation involves low- and high-pressure testing of every pressure-control component. Pressure testing verifies pressure integrity of blowout preventers (BOPs), BOP inlet valves and kill lines, treating lines, choke lines, CT string, and dual-flapper check valves.

Pressure testing, contrary to other CT operation processes, requires a minimum number of personnel and must be performed sequentially. Pressure testing is also suited for improvement following the systematic improvement methodology. The pressure-testing process cloaks many sources of waste that were unrecognized previously.

Process Management. A proactive, carefully managed approach was deemed necessary to achieve a true step change in performance. The systematic improvement methodology was used to monitor the entire process on an individual-task level. Pressure-testing sequences were managed by individual tests and then the subtasks necessary for each test. Investigating the process on such a detailed scale allowed the root causes of inconsistency and poor performance to be analyzed.

Areas of Improvement. Significant pressure-testing improvement was observed after implementing the systematic improvement methodology. The enhanced performance was a product of eliminating component redundancies, reducing failed pressure tests, minimizing transition time, optimizing pressure-control components, increasing offline testing, managing performance, and implementing software enhancements.

Component Redundancies. Risk aversion, when applied specifically to pressure testing, materializes in the form of redundant components or duplicate processes that are not required by regulations.

Failed Pressure Tests. Failed tests, referred to as NPT, are an obvious source of waste while pressure testing. Reducing the number of pressure tests in the series ultimately increases performance through limited exposure to failure modes.

Transition Time. Transition time must be minimized to increase the percentage of total process time that is completed as value added. Transition time, in many cases, can exceed total NPT from failed tests. Transition time warrants a careful focus on managing the tasks completed during this period.

Offline vs. Online Testing. Pressure testing off line is highly preferred to online testing. When permitted and approved, offline testing allows for a large percentage of pressure tests to be performed while other activities progress.

Resources Required for Continuous Improvement

Personnel. Continuous improvement in surface processes requires an efficiency champion (EC). This person most often is a service-company employee with excellent familiarity with CT surface activities and work-flow processes. However, the EC title is reflective of any individual, whether operator, service company, or third-party employee, who possesses the primary objective of implementing the systematic methodology to improve efficiency. Therefore, the EC position is not limited to engineering personnel but is expanded to a variety of positions, such as service-quality coaches, internal auditors, or supervisors.

Software Systems. Manually tracking each process is a heuristic approach most suited for demonstrating the effectiveness of the systematic approach. However, manual tracking is not recommended for long-term evaluation of performance because of the inherent amount of time and effort required. To ensure continuous improvement in every job, the systematic efficiency-improvement methodology must be automated so that information can be collected, stored, and analyzed without conscious effort.

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 184779, “Consistent, Systematic Approach to Deepwater Coiled-Tubing-Efficiency Improvement Substantially Reduces Operational Time, Gulf of Mexico,” by Peter Weiland, SPE, Alexander Rudnik, SPE, and Eric Gagen, SPE, Schlumberger, prepared for the 2017 SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition, Houston, 21–22 March. The paper has not been peer reviewed.

Systematic Coiled-Tubing-Efficiency Improvement Reduces Operational Time

01 June 2017

Volume: 69 | Issue: 6


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