This paper describes a one-step fracturing/gravel-pack (frac-andpack) completion procedure conducted on the BP Exploration Amberjack platform beginning in early 1992. This platform is 35 miles southwest of Venice. LA. The first four completions on this platform had an average positive skin values of 21. The goal of the frac-andpack procedure was to reduce these skins to nearly zero. In total, 24 frac-and-pack operations were performed. Details of the fracture design, pre fracture testing. fracture design and execution, and production response and a continuing optimization program are discussed. The fractures were performed with the screens in place with the gravel pack after the fracturing operation. The treatments were designed for the tip screenout technique 1 ,2 to create wide fractures and to provide proppant loadings exceeding 8 Ibmlft 2 .This paper presents the trend of the declining skin values. along with a discussion of time-dependent skins. The changes in fluids. breakers, and proppants are also presented. The average skin on 14 frac-and-pack completions was 5.3. The average skin on the final eight completions was 0.2. Design and ExecutionIntroduction. The BP Exploration Amberjack Project (Mississippi Canyon Block 109) is 35 miles southeast of Venice. LA. and 18 miles from the Mississippi River delta. The water depth ranges from 850 to 1,500 ftin the block. Acquired in 1983. the field is on the eastern side of the Plio-Pleistocene flexure trend of the Gulf of Mexico.A persistent problem with offshore gravel packs has been the presence of high positive skins measured on transient-pressure tests. Positive skins of 10 to 50 are routinely measured on all but very short intervals using state-of-the-art gravel-packing technology. Our early experience on the Amberjack platform showed a clear trend of higher-than-desired skins. On the first four wells. a viscous slurry prepack was pumped into the perforations. and after cleanout, the screens were run and a water pack was pumped. Studies have shown that using water as the carrier fluid provides a uniform, tight pack. Despite this, high positive skins were still measured.We think that a primary reason for the high skins may be that the prepack techniques currently used may not place sufficient sand in all perforations. A second and potentially more important reason is that the cleanout operation may destroy the hydraulic continuity between the perforations and the packed screens. Fracturing followed by gravel packing provides excellent vertical proppant distribution. This ensures that the connection among the formation, perforation, and packed screen is maintained if the operation is performed in one step. After a thorough review, a decision was reached to implement the frac-and-pack process with the screens in place.The fracturing treatments were performed with the screens in place, the crossover tool in the circulating position. and a closed choke on the annulus. The desired proppant volume is placed at fracture rates followed by an appropriate gravel-pack volu...
Effective internal and external cooling of airfoils is key to maintaining component life for efficient gas turbines. Cooling designs have spanned the range from simple internal convective channels to more advanced double-walls with shaped film-cooling holes. This paper describes the development of an internal and external cooling concept for a state-of-the-art cooled turbine blade. These cooling concepts are based on a review of literature and patents, as well as, interactions with academic and industry turbine cooling experts. The cooling configuration selected and described in this paper is referred to as the “baseline” design, since this design will simultaneously be tested with other more advanced blade cooling designs in a rotating turbine test facility using a “rainbow turbine wheel” configuration. For the baseline design, the leading edge is cooled by internal jet impingement and showerhead film cooling. The mid-chord region of the blade contains a three-pass serpentine passage with internal discrete V-shaped trip strips to enhance the internal heat transfer coefficient. The film cooling along the mid-chord of the blade uses multiple rows of shaped diffusion holes. The trailing edge is internally cooled using jet impingement and externally film cooled through partitioned cuts on the pressure side of the blade.
Cooling of turbine hot-gas-path components can increase engine efficiency, reduce emissions, and extend engine life. As cooling technologies evolved, numerous blade cooling geometries have been and continue to be proposed by researchers and engine builders for internal and external blade and vane cooling. However, the impact of these improved cooling configurations on overall engine performance is the ultimate metric. There is no assurance that obtaining higher cooling performance for an individual cooling technique will result in better turbine performance because of the introduction of additional second law losses, e.g., exergy loss from blade heat transfer, cooling air friction losses, and fluid mixing, and thus, the higher cooling performance might not always be the best solution to improve efficiency. To quantify the effect of different internal and external blade cooling techniques and their combinations on engine performance, a cooled engine model has been developed for industrial gas turbines and aero-engines using MATLAB Simulink. The model has the flexibility to be used for both engine types and consists of uncooled on-design, turbomachinery design, and a cooled off-design analysis in order to evaluate the engine performance parameters by using operating conditions, polytropic efficiencies, material information, and cooling system information. The cooling analysis algorithm involves a second law analysis to calculate losses from the cooling technique applied. The effects of variations in engine parameters such as turbine inlet temperature, by-pass ratio, and operating temperature are studied. The impact of variations in metal Biot number, thermal barrier coating (TBC) Biot number, film cooling effectiveness, internal cooling effectiveness, and maximum allowable blade temperature on engine performance parameters are analyzed. Possible design recommendations based on these variations, and direction of use of this tool for new cooling design validation, are presented.
Effective internal and external cooling of airfoils is key to maintaining component life for efficient gas turbines. Cooling designs have spanned the range from simple internal convective channels to more advanced double-walls with shaped film-cooling holes. This paper describes the development of an internal and external cooling concept for a state-of-the-art cooled turbine blade. These cooling concepts are based on a review of literature and patents, as well as, interactions with academic and industry turbine cooling experts. The cooling configuration selected and described in this paper is referred to as the “baseline” design, since this design will simultaneously be tested with other more advanced blade cooling designs in a rotating turbine test facility using a “rainbow turbine wheel” configuration. For the baseline design, the leading edge is cooled by internal jet impingement and showerhead film cooling. The midchord region of the blade contains a three-pass serpentine passage with internal discrete V-shaped trip strips to enhance the internal heat transfer coefficient (HTC). The film cooling along the midchord of the blade uses multiple rows of shaped diffusion holes. The trailing edge is internally cooled using jet impingement and externally film cooled through partitioned cuts on the pressure side of the blade.
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