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Abstract Early identification of differential depletion in stacked reservoir sands, before water or gas breaks through, is the key to optimal reservoir drainage. However, hitherto it has not been possible to monitor reservoir pressure changes in individual layers after a well has been put on production without installing an intelligent completion or performing a multirate inflow performance relationship (IPR) test. This paper describes a technique allowing individual layer pressures, or gas/oil ratios (GOR), to be monitored continuously during production. The technique employs the use of a rigorous near-well nodal reservoir pressure and thermal model to analyze permanently installed distributed temperature measurements. By modeling a range of typical flowing scenarios we demonstrate that distributed temperature measurements respond to changes in production caused by depletion in individual reservoir layers. We also show that in addition to flow rate determination, layer pressure changes smaller than 10 psi can be detected by changes in the measured temperature profile, as long as there is no breakthrough of gas or water. The model is also used to define the limits of the technique's operating envelope. Increases in the flowing layer GOR will decrease the layers' fluid viscosity, resulting in a change in flow rate together with a decrease in flowing fluid temperature due to the Joule-Thomson effect. Consequently, layers where the GOR increases, identifying early gas breakthrough or fingering, can also be detected using distributed temperature monitoring. The theoretical models are supported by real well examples, where the calculation of different layer pressures caused by depletion is confirmed by shutting in the well and observing the resulting crossflow with permanently installed distributed temperature monitoring. These models, along with continuously monitored temperature profiles, can be used to refine reservoir models and thus improve overall field recovery. Introduction There isno doubt that monitoring layer production and pressures is the key to optimal reservoir drainage in stacked reservoirs. Knowing which layers are depleting and at what rate is information that can be directly input into the reservoir model. Well tests, by their very nature, average the buildup pressure in a multilayered system. Therefore, if one wishes to measure individual layer pressures only two options are currently available. One can install an intelligent completion and shut-in each zone periodically to obtain a buildup pressure, which can be costly and results in loss of production during the shut-in. Alternatively one can perform a multirate IPR test using a production logging tool (PLT) log, which again results in loss of production because the well is often shut-in for some time and also needs to be flowed at a reduced rate. There is now a third alternative that does not require shutting in the well or reducing flow rate, and it can be performed any time during the life of the well. It is based on the fact that over time the individual layer flow contributions will change naturally as the reservoir layer pressure changes. Flow distribution is monitored using a permanently installed fiber-optic distributed temperature system (DTS). During early production, a near-wellbore reservoir model is characterized to match the well-bore temperature profile calculated from the thermal model to the early measured DTS data when reservoir layer pressures and other parameters are known (i.e. from logs). As the flow profile changes with time, the model can then be used to predict the reservoir pressures from the change in temperatures. Of course, this could be achieved by running a series of production logs during the life of the well; however, this option will require intervention and is not always practical. Further benefits of continuous monitoring using DTS systems are that if a particular layer's GOR increases, this can also be identified and evaluated using the DTS system.
With the development of marine oil&gas exploration technology, flexible risers are frequently used in marine engineering.The paper introduces key procedures and measuring methods of the off shore experiment of this new-type non-metallic composite flexible risers. It inspects the actual experimental operating performance, anti-tension and anti-compression strength, reliability, etc. Results indicate that non-metallic composite flexible risers perform well in anti-bending and anti-compression. It present an atypical catenary shape in water. Bending curvature near the touch down point increases obviously; the top tension is effected by bulge process and wave-current. The bigger the internal pressure is, the smaller the tensile force is. Because of buoyant force, the tensile force along the axis decreases gradually; the internal pressure shared by skeleton layer among all the layers is the largest, arriving at 54.5%.
In recent years, there are more and more oil-gas explorations and production activities. Applying new technology and developing present technology are becoming the theme of modern ocean engineering field. The increase of world petroleum industry and frontier of technology innovation are gradually depending on oil and gas exploitation in deep water (Krishnan, Asher, Kan, and Popelar, 2016). Deep-sea risers are the key parts in connecting subsea production systems and surface unit. In structural shape, deep-sea risers can be divided into Steel Catenary Riser(SCR), Top Tension Riser(TTR), Flexible Riser and Hybrid Riser (Dumitrescu, Pulici and Trifon, 2003). The development of flexible risers may be dated back to late 1970s. Although it started late, it developed promptly. High-rigidity spirals inside the compound structures can strengthen metal layer to guarantee density and the low-rigidity polymer sealant can ensure the integrity of the fluid. In the outside and inside loading conditions, these layers can glide mutually to ensure that flexible risers are equipped with the feature of low warp rigidity (Bectarte and Coutarel, 2004). Besides, spirals can be replaced by various materials to strengthen metal layers in order to improve and enhance mechanical properties. Because of these features, flexible risers are becoming the focus of risers worldwide in recent years. In the area of riser laying technology, the experiment of marine risers were conducted through special experimental equipment including pipelaying vessel, etc. Due to sea current and waves, the progressing of pipelaying vessels will lead to the change of pipeline stress, therefore various riser laying methods are formed. The forms mostly used are S-Shaped laying(Baker and McClure, 2002), roll-shaped laying (Choi, 1999), J-shaped laying (Féret, and Bournazel, 1987), trailer-laying (Li, Zhong, Jiang, He, and Sun, 2016), etc. The paper depends on the actual and correct evaluation of system performance in the process of experiment through roll-shaped laying. This evaluation not only explores the details of technology and the function limits of every designing, but also analyzes the reliability of the designing and the interface requirements, and the cost. The paper introduces the process of new non-metallic composite flexible risers installation experiment, analyzes the measured data and confirms the posture, stress and law of motion.
Cable fairings are routinely used on towed instruments where tow speeds are in excess of 3 knots and here good depth performance is desirable In order to minimize the cable fairing drag the correct choice of fairing for the application is essential. Typical oceanographic or survey applications utilize wires of 8 to 20 mm diameter at tow speeds of 3 to 10 knots. This corresponds to a Reynolds number range of 10000 to 100000 In terms of aircraft aerodynamics these Reynolds numbers are low. Most of our knowledge of foil section performance comes from model studies of aircraft wings at Reynolds numbers of 1 to 10 million At these higher Re values boundary layer transition occurs close to the leading edge, and consequently most of the boundary layer on the surface is turbulent. At the Reynolds numbers typical of oceanographic fairings the laminar boundary may persist longer, and laminar separation bubbles are more likely to occur. Furthermore early trailing edge flow separation may be precipitated on poor designs which significantly increases the drag.
The laminar boundary layer is actually very beneficial in that it exerts much less skin friction drag than the turbulent boundary layer. It is possible to design section profiles which make use of this by encouraging the laminar boundary-layer to remain attached and delaying transition. The secret lies in the form of the pressure distribution on the surface Figure 1 shows the inviscid theoretical pressure distribution calculated for one of the best commercially available cable fairings. The flow visualization sketch for a Reynolds number of 210 000 is after Henderson (ref 1) who reported the wind-tunnel test results. The rounded nose positions the suction peak close to the leading edge, and the remainder of the boundary layer is subjected to a destablizing adverse pressure gradient. The laminar boundary layer separates near the suction peak, forming a separation bubble.
Following reattachment the turbulent boundary layer does not survive the long run to the trailing edge and separates early. The resulting drag coefficient is 0.04-approximately four times the drag that might be expected for a section like this at Reynolds numbers in excess of 1 million. Henderson also demonstrated that the fairing stalled at an incidence of 4°, and he calculated that the section aerodynamic centre was located at 15.4% chord. The importance of the aerodynamic centre location is in determining the weathercock stability of the freely pivoted fairing, i.e how well it aligns itself with the flow. The distance between the wire centre and aerodynamic centre on a fairing like this is a direct measure of the weathercock stability In this case Henderson determined the separation to be only about 0 03 c where c is the chord length of the section. The poor performance of this section at RE = 210 000 is entirely due to the behaviour of the boundary layer.
Fig. 1 Inviscid pressure distribution for the commercial fairing section and flow visualization sketch at Re = 210 000 (after Henderson (ref 1) (available in full paper)
Kramer, Patrick (Luna Innovations Inc.) | Grumbach, Christina (The Boeing Company) | Williams, Kristen S. (The Boeing Company) | Feickert, Aaron J. (North Dakota State University) | Friedersdorf, Fritz (Luna Innovations Inc.) | Pennell, Sean (The Boeing Company) | Schultz, Karen A. (The Boeing Company) | Croll, Stuart G. (North Dakota State University)
ABSTRACTRepair and replacement of exterior coating systems that no longer meet aesthetic or protective requirements generate a significant volume of environmentally hazardous waste, which includes the coating material combined with solvents and/or media used to remove the coatings, as well as the waste materials generated in surface preparation and reapplication of the coating system. There are strong economic and environmental drivers to extend the service life of aerospace coatings. However, development, selection, and use of the most durable coatings systems have often been limited by the ability to predict service performance in accelerated tests. Current accelerated test methods do not adequately employ the chemical, thermal, mechanical, or radiative stressors that produce relevant damage mechanisms in coated structures that can be used for accurate quantification of coating performance and service life. Test methodologies are being developed that employ combined environmental and mechanical loading modes to overcome this issue. The mechanisms and kinetics of damage progression are quantified continuously throughout a test using in situ measurements of coating system properties and substrate corrosion. Mechanical test fixtures and simulated structural components are being used to apply stresses to coating systems in accelerated atmospheric test chambers. The combined mechanical and environmental tests are expected to produce failure modes not achieved using traditional atmospheric test chambers. An overview is given of the test methods, in situ measurement systems, coating characterization, and combined effects atmospheric exposure testing.INTRODUCTIONA significant volume of environmentally hazardous waste is generated during repair and replacement of many coating systems such as those applied to the exterior of aircraft. Hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) are needed, often in large quantities, for most remediation activities. The waste streams are associated with not only the chemical strippers and dusts generated during removal but also with substrate pretreatment chemicals that may contain hexavalent chromium, a known carcinogen. The amount of physical blast media and chemical stripper needed for stripping a single aircraft can be on the order of tens-of-thousands of pounds and several hundred gallons, respectively.Current standardized coating testing methodologies have not been suitable for accurately predicting the lifetime and performance of conventional and advanced coating systems on aircraft structures. During service, aircraft coating systems are subject to a combination of dynamic chemical, thermal, mechanical, and radiative stressors. The failure modes driven by the combined influence of all of these stressors are often different than the failure modes induced in standardized test methods. This is because standard methods do not account for mechanical stress and may only consider a single variable at a time. In some cases, components of a coating stack-up are qualified individually and not at the system level where incompatible material properties developed during service conditions lead to cracks and checks in the coatings. The result of the lack of understanding of causes of in-service failures and the inability to replicate them afforded by current test methods is the qualification of sub- optimal material systems that require shortened repair/replacement cycles. New representative coating evaluation protocols are needed to realistically assess the performance of complex coating material combinations, there-by enabling more accurate service life predictions, optimized maintenance intervals, accelerated development of high performance coatings, and ultimately significant reduction in hazardous waste generation.
Abstract In depleted reservoirs producing with high water cuts, it is often difficult to evaluate which intervals are producing oil. Such wells typically use electric submersible pumps (ESPs) to lift the fluids, so logging operations are limited. Even when logging is possible, identifying oil production that amounts to 5% or less from a zone producing water can be a challenge. This problem can be addressed by installing fiber-optic distributed temperature sensors (DTS) below the ESP of a well producing oil with a high water cut from multiple reservoir intervals. Differentiating between water and oil production with a DTS system is not directly possible at such high water cuts; however, by switching the water injection support from surrounding injectors on and off, the reservoir intervals being supported by each injector can be identified and the injection pattern that maximizes oil production can be found. The information obtained will allow an operator to shut off the water-only producing intervals during a subsequent workover, resulting in increased oil production from the well. This novel application of DTS monitoring below ESP pumps in depleted, high-water-cut wells and the low-cost monitoring procedure employed has the potential to significantly increase oil production in old oil fields under water flood.