Interpretation of transient temperature data from Permanent Down-hole Gauges (PDGs)
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With the installation of Permanent Down-hole Gauges (PDGs) during oil field development, a large volume of high resolution pressure, temperature and sometimes flow-rate data are available for real-time and continuous reservoir monitoring. In practice, interpretations of these data can optimize well performance, provide information about the reservoir and continuously calibrate the reservoir model. Although the wellbore is in a non-isothermal environment, heat transfer between the fluid in the wellbore and the formation is often ignored and temperature is usually assumed to be constant in the process of data interpretation, leading to misunderstanding of the pressure profile. Furthermore, the pressure transient analysis (PTA) often fails to determine accurate flow regimes, and may be erroneously applied in nonlinear reservoir-well systems. These problems motivated my detailed analysis of temperature data. In this thesis, firstly, a non-isothermal wellbore model that is capable of predicting the temperature, pressure, and flow-rate profiles under multi-rate and multiphase production scenarios is established. Then this numerical wellbore model is coupled with a reservoir model to reproduce the transient temperature behaviour at gauge locations. Secondly, a new workflow for integrating transient down-hole data processing is introduced. The relationship between temperature change and flow-rate change is interpreted and a new nonlinearity diagnostic function (𝐴𝑇𝑢𝑟𝑐) is presented. Thirdly, new procedures of model-independent transient temperature analysis are performed, followed by diagnosing the wellbore storage regime, verifying the PTA interpretation results, and reconstructing the flow-rate history using transient temperature data. Several case studies are conducted to demonstrate how transient temperature analysis, along with the transient pressure analysis can greatly reduce the uncertainties in well testing interpretation. The applications of both synthetic datasets which are simulated by the fully coupled wellbore-reservoir model and real field datasets demonstrated that the temperature data can provide additional constraints for pressure analysis. Additionally, the reliability of the developed methods which reveal complementary reservoir information from transient temperature data has also been verified.