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Modeling reservoir temperature transients, and matching to permanent downhole gauge (PDG) data for reservoir parameter estimation

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Investigator: Obinna Duru

Modeling reservoir temperature transients, and matching to permanent downhole gauge (PDG) data for reservoir parameter estimation

Background and Motivation

Over the last decade, permanent download gauges (PDGs) have been used to provide a continuous source of downhole data in the form of pressure, temperature and sometimes flow rate. The tools provide access to data acquired continuously over a large period of time and containing reservoir information at a much larger radius of investigation than conventional wireline testing.

The behavior of pressure transients in reservoir and wellbore flow has been studied extensively, and applied in conventional well test analysis for reservoir description, parameter estimation for characterization and evaluation of well performance. In recent times, with convolution and deconvolution, filtering and tuning the data, conventional pressure transient analytical methods have also been applied to pressure data from permanent downhole gauges.

However, in the development of pressure transient analytical methods, it has been assumed that the temperature distributions in the reservoir and production zone are isothermal. The temperature changes associated with fluid flow had been considered to be relatively small and hence negligible for any consideration in the analysis of flow behavior of most fluids.

An analysis of temperature measurements, at a finer scale using continuous data from PDGs, has shown that the temperature of the fluids responds to changes in flow conditions in the reservoir and production zone. Generally, the flow is not isothermal when the scale of observation and resolution of the temperature data is reduced. This research is motivated by the possibility of identifying the underlying physical phenomena responsible for this temperature transient behavior and application to reservoir characterization and evaluation of well performance.

Problem Description

Many attempts at developing interpretation method for temperature profiles in wellbore-reservoir systems have remained largely qualitative. Most of the analyses have concentrated on wellbore thermal exchanges due to conduction and convection, assuming that the produced fluid enters the wellbore at the geothermal temperature (Maubeuge,1994). Others have attempted the study of thermometric fields in reservoirs and porous systems, but have constrained the analyses to convective effects only in steady-state formulations. A few have considered the effects of heating or cooling of the produced fluid before it enters the wellbore due to factors like the Joule-Thomson effect, adiabatic expansion and viscous dissipation.

This work aims to solve the problem of modeling the reservoir thermometric effects, as convective, conductive and transient phenomena. The contributions of compressibility and viscous dissipation are also included.