Browsing by Subject "Perforation"
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Item A combined experimental and modeling study of low velocity perforation of thin aluminum plates(2015-12) Simpson, Gary Forest Jr.; Ravi-Chandar, K.; Landis, ChadThis work conducts a combined experimental and modeling study of low velocity projectile perforation of thin AA5083-H116 aluminum plates. Experiments were performed in order to characterize the candidate material and calibrate simple and easy to implement empirical models for both the material response and ductile failure behavior. Quasi-static tensile tests were performed in order to investigate the Portevin-Le Chatelier effect common to 5xxx series aluminum as well as to calibrate a Ramberg-Osgood representation for the material stress-strain curve. The material response at strain rates up to and exceeding 104 s-1 was investigated by means of an electromagnetically driven ring expansion test, characterizing the potential strain rate sensitivity of the material. Additionally, the failure behavior and potential damage accumulation of the material were evaluated using an interrupted, multiple loading path strain-to-failure test, validating a Johnson-Cook failure model for use in numerical simulation. Low velocity ballistic impact and perforation experiments, investigating several specific mechanisms of deformation and failure, were conducted and modeled by implementing the developed material and failure model in 3D finite element simulations.Item Hydraulic fracturing optimization : experimental investigation of multiple fracture growth homogeneity via perforation cluster distribution(2016-05) Michael, Andreas; Olson, Jon E.; Balhoff, Matthew THydraulic fracturing is a reservoir stimulation technique used in the petroleum industry since 1947. High pressure fluid composed mainly of water generates cracks near the wellbore improving the surrounding permeability and enhancing the flow of oil and gas to the surface. Advances in hydraulic fracturing coupled with developments in horizontal drilling, have unlocked vast quantities of unconventional resources, previously believed impossible to be produced. Fracture creation induces perturbations in the nearby in-situ stress regime suppressing the initiation and propagation of other fractures. Neighboring fractures are affected by this stress shadow effect, causing them to grow dissimilarly and they receive unequal portions of the injected fluid. Numerical simulation models have shown that non-uniform perforation cluster distributions with interior fractures closer to the exterior ones can balance out these stress shadow effects, promoting more homogeneous multiple fracture growth compared to uniform perforation cluster distributions. In this work, laboratory-scale tests on three perforation configurations are performed on transparent specimens using distinctly colored fracturing fluids such that fracture growth can be observed. A normal faulting stress regime is replicated with the introduction of an overburden load in a confined space. The results have shown that uniform perforation spacing configurations yields higher degree of fracture growth homogeneity, as maximum spacing minimizes stress shadow effects, compared to moving the middle perforation closer to the toe, or heel of the horizontal well. The experiments also showed a proclivity to form one dominant fracture. Time delay, neglected in most theoretical modelling studies, between fracture initiations is found to be a key parameter and is believed to be one of the major factors promoting this dominant fracture tendency along with wellbore pressure gradients. Moreover, in several cases, the injected bypassed perforation(s) to generate fracture(s) downstream. Finally, the compressibility of the fracturing fluid triggered somewhat unexpected transient pressure behavior. The understanding of the stress shadow effects and what influences them could lead to optimization of hydraulic fracturing treatment design in terms of productivity and cost. Therefore, achieving more homogeneous multiple fracture growth patterns can be pivotal on the economic feasibility of several stimulation treatments.Item Multi-frac propagation in unconventional shale(2015-12) Asiamah, Nana Kwadwo Sasu; Olson, Jon E.; Schultz, RichardIn recent years, the Zipper-Frac technique has become one of the most widely used stimulation techniques in the oil and gas industry. The efficiency in this technique lies in minimizing stress shadows between adjacent stimulated fractures while maximizing fracture network and surface area in order to increase fluid production. The Zipper-Frac technique stimulates two parallel horizontally drilled wellbores, alternating between perforation clusters, while maintaining pressure in the previously fractured wellbore or perforation cluster. This study analyzes and discusses multi-fracture experiments in the laboratory that mimic Zipper-Frac results in unconventional shale. The experiments were conducted with two intended outcomes: (i) to examine how time-dependent pressure decay limits stress shadow effects and (ii) to investigate fracture complexity developed in Zipper-Fracs. To achieve these objectives, laboratory experiments were conducted on synthetic blocks (gypsum cement) of three layers (hydrostone, plaster and hydrostone, respectively). The experiment was conducted on 12 samples. Six samples were fractured with a pressure hold-up technique, where the in-situ stress after fracturing was above the fracture closure stress (FCS); and the other six were fractured with a pressure bleed-off technique, where the pressure was bled-off below the FCS. The results indicate is that greater well spacing and bleeding off pressure in fractures post-treatment result in longer and straighter fractures, hence minimal stress shadow, while closer well spacing and maintaining pressure in fractures post-treatment caused more non-planar fracture paths and less created fracture length, hence stronger stress shadow. Consequently, it can be inferred that less complexity would result with the bleed-off method, but this gives greater fracture surface area because of the greater achieved lengths.