Transient Non-isothermal Wellbore Fluid Flow and Heat Transfer Modeling

Mehdi Bahonar


The number of sophisticated wells that are annually being drilled in the globe is continuously rising. During the development of wells, modeling and simulation techniques have also grown very fast but they still need further intensive investigation.

In the first part of the study, a fast numerical transient non-isothermal multiphase wellbore simulator has been developed and validated through comparisons with field experiments and prediction of other models. Then two important issues related to heat transfer in the wellbore simulation that have received little or no attention in the literature, have been thoroughly analyzed using this thermal wellbore simulator, and its merits for accurate prediction of casing temperature have been demonstrated. The first issue pertains to systematic and rigorous comparisons between some of the existing models for estimating the formation temperature, and the second one deals with the development of new approaches to model the transient heat transfer from the wellbore tubing up to the formation. Appropriates recommendations have been also made in dealing with each issue to achieve higher accuracy for a given wellbore simulation process.

In the second part of the study, a fully-implicit non-isothermal coupled wellbore/ reservoirs model has been developed and validated with analytical models. One of the special features of this simulator that has increased the overall accuracy of the model is the implementation of  a strong wellbore heat loss model. This model has emerged as a result of the experiences that have been acquired from previous part. Another feature of this non-isothermal models it that it can be easily downgraded to its equivalent isothermal counterpart. Finally the developed simulators have been implemented for a closed and detailed study of gas well tests. In particular, thermal effects on the behavior of derivative plots and the sandface flow rate of high-temperature and high-pressures gas reservoirs have been studied. It has been found that if these complicated effects are not recognized properly, the acquired results particularly via analytical modes may be misleading or a test may be designed improperly. The developed non-isothermal coupled wellbore/reservoir simulator allows overcoming all these deficiencies.