Fluids produced from deep underground reservoirs may result in exponential increase in temperature. It is a consequence of adiabatic fluid decompression from the inverse Joule Thomson Effect (JTE). The phenomenon requires analysis in order to avoid any operational risks. This study evaluates the JTE upon decompression of black oil in high pressure-high temperature reservoirs. Also the effect caused by the presence of water and brine on the black oil is studied.

The final temperature is calculated from the corresponding energy balance at isenthalpic and non-isenthalpic conditions. It is found that the final temperature of black oil increases upon adiabatic decompression. In the case of the isenthalpic process at initial conditions of the reservoir, e.g. 150°C and 1000 bars, it is found that the final temperature can increase to 173.7°C. At non-isenthalpic conditions the final temperature increases as well, but the increase is less. The effect of water is studied at different water fractions; it results in lower increase of the final temperature than observed for black oil. The presence of brine in black oil is also studied at different brine fractions. The addition of brine increases the final temperature but the increase is less than for pure black oil. Therefore, the presence of water and brine in black oil diminishes the heating effect observed initially for black oil.

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