Browsing by Subject "Water hammer"
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Item Pressure transients in wellbores : water hammer effects and implications for fracture diagnostics(2010-12) Mondal, Somnath; Sharma, Mukul M.; DiCarlo, DavidA pressure transient is generated when a sudden change in injection rate occurs due to a valve closure or injector shutdown. This pressure transient, referred to as a water hammer, travels down the wellbore, is reflected back and induces a series of pressure pulses on the sand face. This study presents a semi-analytical model to simulate the magnitude, frequency and duration of water hammer in wellbores. An impedance model has been suggested that can describe the interface, between the wellbore and the formation. Pressure transients measured in five wells in an offshore field are history matched to validate the model. It is shown that the amplitude of the pressure waves may be up to an order of magnitude smaller at the sand face when compared with surface measurements. Finally, a model has been proposed to estimate fracture dimensions from water hammer data.Item Water hammer fracture diagnostics(2014-12) Carey, Michael Andrew; Sharma, Mukul M.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 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. This study confirms that created hydraulic fractures alter the period, amplitude, and duration of the water hammer signal. Water hammer pressure signals were simulated with a previously presented numerical model that combined the continuity and momentum equations of the wellbore with a created hydraulic fracture represented by a RCI series circuit. Field data from several multi-stage stimulation treatments were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained. Equivalent fracture dimensions were calculated from R, C, and I, and were in agreement with acquired micro-seismic SRV. Finally, the obtained R, C, and I values were compared to SRV and production log data. Capacitance was directly correlated with SRV, while resistance was inversely correlated with SRV, and no correlations with production data were observed.