The Use of Bottomhole Temperature Variations in Production Testings

Abstract

SPE Member Abstract Temperature data recorded during production testing have been interpreted and the results found to be a useful source of information to supplement the pressure data. Increases in bottom hole temperature pressure data. Increases in bottom hole temperature while flowing are explained by the Joule-Thomson inversion effect. During shut-in periods, the temperature declines and it has been found that the fall-off can be analysed using transient well test analysis techniques. Three field examples are presented where effects attributed to reservoir presented where effects attributed to reservoir geometry yielded similar responses on both the pressure and the temperature analyses. A fourth pressure and the temperature analyses. A fourth example demonstrates how the analysis wrongly interpreted variations in temperature for no-flow boundaries. This paper shows how the variations in temperature during the shut-in behaves in a similar manner to the transient pressure behaviour in a wellbore. A procedure for estimating the static reservoir temperature is also recommended. Introduction The process of drilling a well will lead to cooling of the formation locally around the wellbore, due to the circulation of cooler fluids. After the circulation has stopped, the temperature builds up to its initial value as the surrounding formation supplies heat to the cooler region. Producing the well will speed up this process since fluid from further out is introduced to the near wellbore region. An additional form of wellbore heating may occur due to expansion of the reservoir fluid as it flows into the wellbore. As a result of heating due to expansion (Joule-Thomson inversion), the wellbore may be heated to above the normal static reservoir temperature during production. However, due to the very low diffusivity to heat, the increase in temperature is only a very localised effect around the wellbore. During the shut-in period the temperature in the wellbore declines. It has been observed that this decline can be analysed qualitatively by the derivative approach as used in well pressure test analysis. Several examples are presented where no-flow boundary effects appeared presented where no-flow boundary effects appeared consistently in both the pressure and temperature analyses. This paper discusses why the wellbore temperature changes during production. The diffusivities for pressure and heat are examined and it is shown how pressure and heat are examined and it is shown how effects observed from the temperature analysis cannot be the result of the heat diffusivity wave. The effect of the pressure build-up on the recorded temperature during the shut-in is discussed and presented as a possible explanation for the presented as a possible explanation for the observations made. WELLBORE TEMPERATURE VARIATIONS DURING PRODUCTION TESTING During drilling the temperature of the near wellbore region is reduced due to the circulation of cooler fluids. After the circulation has stopped the temperature in the wellbore gradually increases to the static reservoir temperature. When flowing, warmer fluids are introduced to the cooler near wellbore region, thereby helping the recovery in temperature. In addition there can also be a temperature increase associated with expansion of the reservoir fluids i.e. Joule-Thomson inversion. P. 423