A sudden change in flow in a confined system results in the formation of a series of pressure pulses known as a water hammer. Pump shutdown or valve closure at the conclusion of a hydraulic fracture treatment frequently generates a water hammer, which sends a pressure pulse down the wellbore that interacts with the created fracture before returning towards the surface. The result is a pressure profile that consists of a series of oscillations that attenuate over time due to friction. Created hydraulic fractures have been shown to alter the period, amplitude, and duration of the water hammer signal. The goal of this study was to simulate the water hammer response of hydraulically fractured wells, and quantify how fractures affect the response.Water hammer pressure signals were simulated in this study with a numerical model that combined the continuity and momentum equations for the wellbore with a hydraulic fracture represented by a circuit with a resistance, capacitance, and inertance (R, C, and I) connected in series. To test how each variable affected the water hammer signal, the R, C, and I variables were each individually altered through a range of values while all else was held constant. Furthermore, field data from several fractured wells were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained.Changes in the fracture resistance, capacitance, or inertance are shown to alter the simulated water hammer signature. Variations in capacitance alter the period of water hammer oscillations and the average pressure sustained by the water hammer. Variations in resistance affect the initial water hammer amplitude and the rate of oscillation decay. Variations in inertance affect the period of the water hammer. Field data from hydraulically fractured wells was successfully history matched, and R, C, and I values were obtained for each well. Fracture length, height, and width were calculated from derived expressions based on R, C, and I, and were in good agreement with other fracture parameter estimation methods.The results from this work indicate that the water hammer signals at the conclusion of a hydraulic fracturing treatment are affected by the created hydraulic fractures. Thus, water hammer fracture diagnostics will yield important information about the created fracture such as the relative size (derived from the calculated length, width, height) and connectivity (indicated by the resistance value, R) to the wellbore.
There are two types of sand retention tests generally used in the industry to evaluate the performance of sand control screens for standalone screen applications: pre-pack tests and slurry tests. They represent complete hole collapse and gradual rock failure around the wellbore, respectively. In this paper, we present analytical results as well as Monte Carlo simulations to estimate sand production in slurry type sand retention tests with square mesh screens taking into account the full particle size distribution of the formation sand. We also compare the model results with experimental data and demonstrate that this approach can be used to predict sand production for different sand size distribution/screen size combinations without the need for physical tests. This work augments previously published slurry test models that were limited to wire-wrap screens, and enables comparison of the performance of square mesh screens to wire-wrap screens. The analytical model along with Monte Carlo simulations provide a direct and reliable way to estimate the amount of sand that will be produced for a given sand size distribution and a given screen size. Since the proposed methods are much more quantitative, they represent a significant improvement over current methods that rely on single design points or rules of thumb for screen selection.
Summary Woven-metal-mesh sand screens, commonly known as premium screens, have been used extensively by the industry. Sand-retention testing is often executed to evaluate the performance of these screens and to establish empirical guidelines for screen-size selection. These tests are tedious, however, and the results are prone to artifacts and have been used, at best, to correlate trends in sandretention performance with select sand-size-distribution parameters. A new method incorporating results from numerical modeling, in addition to experimental data, is presented to estimate the mass and size distribution of the produced solids in prepack sandretention tests (SRTs) through premium screens. This method provides a fast, reliable correlation to estimate sand production through premium mesh screens when the size distribution of the formation sand is known. This paper presents results from a wide range of pre-pack sand-retention experiments. In these tests, which represent complete hole collapse, the mass of sand produced and its size distribution over time are measured. Results of 3D, discrete- element computer simulations of woven-screen geometry placed in contact with granular sandpacks of approximately 100,000 particles are also presented. On the basis of both the simulations and the experiments, a new method for screen selection is presented. This method is based on a correlation that allows one to use the entire sand-size distribution of the formation sand and to estimate the mass and size distribution of the produced sand. The method is validated by comparisons with experimental data. A new method and new correlations for estimating the mass and size distribution of produced solids in prepack tests through premium screens are presented. Key differences in sand-retention mechanisms between premium screens and wire-wrapped screens (WWSs) have been identified. The method uses the entire-formation sand-size distribution (as opposed to a single design point), and has been validated with laboratory tests. The method also helps in screening anomalous test results.
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