Distributed temperature sensing (DTS) is a technique to obtain real-time temperature well logs which are used for several applications such as production allocation, heavy oil thermal recovery (e.g., steam-assisted gravity drainage, SAGD) steamwell management, and well-integrity monitoring. This system is based on measuring scattered light at more than one wavelength from an optical fiber placed along the well.An issue arises when the attenuation of the optical fiber changes with time by different amounts at the different wavelengths used causing degradation in accuracy of the measurement. This differential loss can be compensated for by connecting both ends of the optical fiber to the DTS instrument in a double-ended (DE) configuration. However, it is not always possible to operate in DE configuration because of other constrains in the design such as lack of space or restricted number of penetrations in completion equipment. Single-ended (SE) operation configuration has been used in these cases, exposing the monitoring system to potential loss of accuracy.An accurate single-ended (ASE) DTS system which provides differential loss measurement and compensation to singleended installations is described. The instrument uses more than one light source to compensate for the optical-fiber differential losses at the relevant wavelengths. This compensation is applied continuously without the need of external recalibration. A system operating on this principle has been used for some time on single-mode fibers, and recent technical advances have enabled its application to multimode fibers.Laboratory-test and field-test results are presented showing a dramatic improvement in accuracy in cases where differential losses have developed. Comparative data using DE, SE, and ASE DTS systems are presented showing cases in which optical fibers were subjected to extreme environments where the effect of differential loss is accentuated. Examples are shown in which errors of up to 100°C caused by differential loss were automatically corrected in real time by the ASE DTS instrument.
This paper summarizes enabling technologies that operators can utilize when planning their field lifecycles, from development and construction through to decommissioning. By approaching field development in a holistic manner, it is possible to minimize total expenditure (TOTEX; the sum of both capital and operational expenditures), whilst also maximizing return on investment and hydrocarbon recovery. With long-term regulatory compliance and production enhancement in mind, early introduction of flexibility into a subsea field infrastructure can enable simplified well or equipment access for common life of field activities, such as erosion sensor replacement. The resulting systems also permit execution of appropriate interventions by utilizing modest and therefore lower cost multi-service vessels (MSV) in place of larger multi-functional rigs at a premium. In the following sections, eight different examples of various subsea production problems are presented, with an overview of how they were successfully resolved. These examples serve to demonstrate that the technologies required to deliver advanced production enhancement solutions are sufficiently mature. The paper concludes by demonstrating how more robust planning and provision for flexibility within subsea production system (SPS) design can lead to more rapid resolution and improved financial returns. Supporting these examples, discussion is provided on how digital analysis and hydraulic treatments can be used to help provide early identification and resolution of issues, thereby themselves acting as means of ultimately achieving production enhancement. By adopting the approaches outlined within this paper, a step-change in production performance is within reach. Subsea systems designed for life of field may include digital technologies to perform on-going advisory services, live fluid sampling capability to assess production performance, and flexible architectures with access points. The optimization of on-going production and necessary intervention can drive informed operational decisions and continual optimization of the field. The results include a reduction in operational risk exposure, maximized ultimate oil recovery, and the ability to effectively manage unplanned changes in performance. This forward-looking approach to field development, combined with a high degree of flexibility, is crucial for supporting prudent investment within today's challenging environment.
In an environment of high activity, large organizational growth, and the nearing of retirement age for a large proportion of the oil and gas industrial workforce (otherwise known as the "big crew change"), there is a high demand for experienced personnel to be correctly placed within an organization to bring maximum benefit for continued growth and knowledge transfer. For a business organization to ensure its success during this challenging period, it must optimize its human capital in a way that will reap the most benefit. Part of this process includes capturing the experienced generation's design knowledge and passing it on in a way that maintains consistency and yet allows the experienced personnel to focus on more business-critical decision making or operational supervisory roles. Configuring the bottomhole assembly (BHA) is typically a crucial point when preparing for well intervention using coiled tubing. Several strategies have been adopted by service providers to standardize and regulate the design stage and ensure continuity through the "big crew change," including:Providing intensive training and mentoring to act as a rapid handover between the experienced and the new generation of tool specialists.Creating and distributing fixed flow chart decision trees throughout the organization.Setting up a specialized group of experienced tool specialists that can be used as a geographically-mobile workforce that services the organization's global needs.Creating a dynamic technology-based computer system that captures the existing field design knowledge and also captures new lessons learned. This paper discusses these strategies, examining the positives and negatives of each approach, and then goes into further detail of how a leading coiled tubing service provider has decided to handle this issue. Introduction - Obstacles to be overcome As tool strings become more complex and spread across a variety of specialized applications, if nothing else changes, the knowledge base of a tool specialist is expected to expand. Due to the industry demand to move the experienced personnel into operational supervisory positions, and expand the working capability; what is needed is a way that allows the expansion rate of the industry to be met immediately by improved efficiency, along with physical work force growth. To maintain industry recognition the service provider must achieve this without any compromise and preferably with an improvement in their service quality. From both a company wide standpoint, as well as at a local level, the latest developments through lessons learnt and new technology developments in well intervention BHA's, from a configuration, and a design improvement standpoint; are all items that must be rapidly available throughout a coiled tubing service providers: tool specialists, sales staff and design engineer communities. Doing this means that every location can rapidly benefit from everyone else's experience, and thus the company as a whole becomes more efficient. Traditional thinking that competency is only achieved through years of seniority, and training based along those lines; alone simply cannot keep up with the current speed the industry demand is growing 1. This attitude must first change, and competency judged by documented training through a variety of media. However even with accelerated training, service providers must complement training with other processes, to achieve complete knowledge sharing through the relevant staff, and to gain the efficiencies needed.
In an environment of high drilling activity and a limited amount of rigs, available alternative completion methods using Wireline or coiled tubing enables a more efficient drilling and completion process. For a successful completion, depth control is critical for the placement of perforating guns and completion hardware. Common practice is to perform the perforating using Wireline, which becomes challenging with wellbore angles over 60 deg. The use of coiled tubing enables the completion of highly deviated or horizontal wellbores, but depth critical operations performed using coiled tubing historically have presented industry challenges. Using the innovative real time depth measurement (RTDM) tool overcomes the limitations of other down hole depth-correlation methods. This paper describes the design, planning and execution of a completion in a horizontal well using coiled tubing and a RTDM tool. Introduction With high demands on the utilization of work over rigs to increase the available production levels; the improved use of resources and cost saving available by using coiled tubing to enable the execution of a sand control completion in a deviated well bore in the Gulf Coast of Mexico has lead some clients to optimize their operations with this technology. Completion Design There are a number of sand screen completions available on the market today from several service providers that can be run on coiled tubing in both mono-bore, or in through tubing1 applications. It is not within the scope of this paper to discuss the individual completion types, but more to cover the similar job design and execution principles that are required in all cases to achieve a successful operation. These principles are explored throughout this paper via a summary of a case history, however to list some main points, the following needs need to be considered as a minimum:–Rig Site Access–Available deck space and loading (crane limitations)–Personnel and equipment logistics–Simultaneous operations–Utilities and amenities–Well Bore Access and Preparation–Tubing Forces–Deployment/Well Control–Well geometry and construction–Well path–Reservoir and Completion–Production characteristics•Pressure•Volumes - solids, liquids and gases–Depth correlation–Ease of running and setting The completion design used, in the case discussed in this paper was specifically chosen for allowing the rig operation to be completed in the quickest possible time, leaving a secure well bore that could then be worked on with intervention technology to finalize the completion at the operators discretion. This allowed the required reservoir which was located in a small window of hydrocarbon bearing rock to be specifically located and produced, with the effect of any potential reservoir damage caused by the drilling process also being minimized or bypassed.
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