| Abstract |
The primary objective of modeling a geothermal system is to be able to predict with some confidence the energy production capacity and longevity of the field under various production and injection scenarios. To achieve this goal, a modeler needs to construct a comprehensive mathematical model based on available data and validate this model against the production history of the field. This, in turn, requires the data associated with the evolution of the field due to its exploitation. Typically, the information related to the variations in the mass flow rate, enthalpy, pressure, temperature and fluid saturation as a function of timeis used to validate the model. The production data is routinely measured at the wellhead whereas most reservoir models canpute the changes in the temperature, pressure, enthalpy, fluid velocity and other physical properties of the fluid at the sandface. To validate any model, wellhead data must be corrected to reflect the downhole conditions. In this paper, we shall confine ourselves to the discussion of computing bottomhole pressures from the measured wellhead data by using a wellbore model. Several wellbore models which canpute wellhead conditions from the given bottomhole data have been cited in the literature. (Sanyal, e t al., 1979; Aydelotte, 1980; Gould, 1974). Such calculations are of interest in predicting the conditions under which an optimum production could be obtained fran a given well. This approach does not suit us since our primary goal is to study the evolution of the field due to production. The following paragraphs are devoted to the discussion of the wellbore model and its describing equations, comparison between the computed and measured pressures and the effect of measured wellhead parameters on the downhole pressures in the well. Finally a wellbore model with multiple inside diameters is discussed and the effect of well scaling on the bottom hole pressures is studied. |