Modelling and analysis of transient temperature in gas reservoir-well systems
Dada, Akindolu Oluwakanyinsola
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The need for more efficient production operations has resulted in a push for greater control and monitoring of wells and reservoirs. This need along with the development of better downhole sensors has resulted in the availability of vast amounts of downhole data. However, data analysis methods have not developed at the same pace as data acquisition, resulting in large amounts of operational data that are left in data silos and never used for any value added activity. Transient pressure and temperature are one of the most commonly measured downhole parameters, and have been proven to be quite valuable. For a long time transient pressure has been used for reservoir characterization and near wellbore analysis, however, transient temperature data has been demonstrated to quite valuable as well, in that it can be used to characterize a formation, provide more detailed near-wellbore analysis and also discriminate between produced fluids. While pressure transient analysis (PTA) methods are quite mature, the same cannot be said of temperature transient analysis (TTA). The major advancements in TTA methods occurred over the last two decades, but have mostly been for slightly compressible fluids. This leaves a knowledge gap, in the area of TTA for gases (i.e. highly compressible fluids) and this work focuses on this. This thesis presents novel transient sandface temperature solutions and methods for analysing the measured transient temperature. Further, since the transient temperature is rarely measured at the mid-perforation point, but at some distance from the mid perforation point, it has to be corrected for the effect of heat transmission in the wellbore before applying the sandface temperature analysis methods. A method for correcting the measured gauge temperature (a process called sandface temperature reconstruction) was presented as well. These methods developed for sandface temperature reconstruction and for analysing the resulting reconstructed sandface temperature were developed for gas producing wells. However, in certain situations these methods can also be applied to liquid producing wells. The combination of the developed sandface TTA methods (for gases) with methods for handling the distant gauge problem makes TTA applicable to a wide range of wells, let alone this can further be combined with the existing liquid TTA methods for a robust multiphase TTA methodology.