The U.S. National Park Service (NPS) maintains and operates numerous park units along the Eastern Seaboard of the United States, extending into the Caribbean to Commonwealth territories like Puerto Rico and the U.S. Virgin Islands (USVI). Parks that dot the eastern shore of the United States are susceptible to damage from hurricane events. Several of these units were in the direct path of hurricanes Irma and Maria during the 2017 hurricane season and suffered considerable damage, including power outages, structural damage, and destroyed equipment.
This paper reports the field results obtained from application of a system that provides both pre-job modeling capabilities and real-time monitoring of maximum stress levels in the entire intervention stack, from the wellhead to the injector assembly.In addition, the paper documents the dynamic movement capabilities recently incorporated in the model and validation of the model calculations. Introduction Reference 2 discusses an intervention riser safety system which has become known as the ? (Zeta) Safety System.This paper documents further development and testing that has been done with this system.The system is composed of two basic components:?model - a numerical dynamic simulation model which models the stresses in an intervention stack.?gauge - a lubricator spool, instrumented with fiber-optic strain gauges, is placed in the intervention stack. It measures axial force, internal pressure, and bending moments in the spool. The initial coiled tubing (CT) field application of this safety system was performed to satisfy several primary objectives, including:Validation of modeled calculations versus field data measured by independent devicesSensitivity of the field stress measurements provided by the systemConfirmation that system design and calibration is sufficiently robust for routine field applications The ability to accurately model dynamic movement of two independent structures was driven by increased utilization of floating structures (TLPs and Spars) being deployed in deepwater projects.The tethered topside structure typically exhibits some amount of horizontal displacement in a figure-eight pattern as a result of wave motion, with the wellhead exhibiting a similar displacement pattern but with differing frequency and amplitude.The intervention stack may experience increased stress levels when each end of the rigid lubricator/riser assembly is attached to these two independently-moving bodies.A dynamic modeling capability incorporated in this model addresses these field conditions. In addition, offshore intervention stacks are becoming taller to accommodate offshore floating structure size, and often pass through multiple deck surfaces that constrain lateral stack movement.This can create a condition whereby conventional safety limits are exceeded.While counter intuitive, removal of lateral stack constraints may actually increase the safety of a given stack.Another finding is that the maximum stack stress may occur in situations where no CT hanging weight is applied to the stack. The pre-job modeling capabilities of the system are used to optimize intervention rig-up design and to determine the probability of exceeding pre-set safety limits during the operation.During the field operation, real-time stress values provided by the system enable informed decisions, rather than a judgment call, to be made if maximum stress levels are approaching unsafe limits.
Some of the most important aspects to consider during the design, construction and productive life of a well are the amount and nature of the risks associated with the conveyance of downhole instruments to acquire critical formation-evaluation data while the hole is open, and downhole toolstrings needed to monitor or service the well after installing the completion and production hardware.Wells with horizontal sections in excess of 5,000 ft present significant challenges to the existing well intervention methods and technologies; in particular, production-logging programs under high-production rates using downhole tractor conveyance have proven to be particularly difficult to plan and execute in these wells. This paper describes the extreme conditions offered by these long horizontal wells, the underlying physics that support modeling of mechanical and hydraulic lift forces, the hazards present when conducting logging operations under flowing conditions using wireline and downhole tractors, the relevant conveyance risk-reduction technologies and methods to successfully plan and execute these extreme operations.To demonstrate the operational merits and practical aspects of the methods and solutions presented, a case study based on a real operation is included.
With the increased popularity of long, deep and tortuous wells, mainly in high-cost operating environments, the risks associated with wireline logging operations and interventions in these modern complex wells have become more acute. Several risk-reduction technologies and forces-modeling software capable of simulating these operations have been developed and successfully applied. This paper describes several high-impact supplementary modeling utilities that have been implemented within a leading forces-modeling software that enable users to adequately plan and execute complex wireline operations. The utilities are designed to perform dedicated analyses using the project data already included in the wireline operation models. The following utilities are presented in this paper: Pump Down AnalysisCable Tension AnalysisFriction Coefficient AnalysisTool Depth Creep AnalysisStuck Pipe AnalysisStuck Wireline/Tool AnalysisTool Free Fall Analysis The effective use of these utilities significantly reduces the non-productive rig time associated with recovery operations and can assist with optimizing pump down operations, accurate positioning of downhole tools, as well as locating tool strings dropped in the well. Use of the utilities can also improve the accuracy of wireline downhole conveyance models while enhancing the ability to perform high-tension operations in a safe and efficient manner. The economic value resulting from the use of these applications is directly associated with the aggregate daily rig cost and the financial cost of the resulting deferred production volume during non-productive time, which together can be in excess of a million dollars a day. This paper provides descriptions and application examples of these supplementary wireline modeling utilities, the logic and calculations supporting them, and the resulting economic benefits they deliver.
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