Browsing by Author "Bahonar, Mehdi"

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    Development of a Thermal Wellbore Simulator with Focus on Improving Heat Loss Calculations for SAGD Steam Injection
    (SPE Reservoir Evaluation & Engineering, 2016) Chen, Zhangxing (John); Xiong, Wanqiang; Bahonar, Mehdi; Dong, Chao
    Typical thermal processes involve sophisticated wellbore configurations, complex fluid flow and heat transfer in tubing, annulus, wellbore completion, and surrounding formation. Despite notable advancements made in wellbore modeling, accurate heat loss modeling is still a challenge using the existing wellbore simulators. This challenge becomes even greater when complex but common wellbore configurations such as multi-parallel or multi-concentric tubings are used in thermal processes such as Steam Assisted Gravity Drainage (SAGD). To improve heat loss estimation, a standalone fully-implicit thermal wellbore simulator is developed that can handle several different wellbore configurations and completions. This simulator uses a fully implicit method to model heat loss from tubing walls to the surrounding formation. Instead of implementing the common Ramey method (1962) for heat loss calculations that has been shown to be a source of large errors, a series of computational fluid dynamical (CFD) models are run for the buoyancy driven flow for different annulus sizes and lengths and numbers of tubings. Based on these CFD models, correlations are derived that can conveniently be used for the more accurate heat loss estimation from the wellbore to the surrounding formation for SAGD injection wells with single or multiple tubing strings. These correlations are embedded in the developed wellbore simulator and results are compared with other heat loss modeling methods to demonstrate its improvements. A series of validations against commercial simulators and field data are presented in this paper.
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    ItemOpen Access
    Transient non-isothermal wellbore fluid flow and heat transfer modeling
    (2011) Bahonar, Mehdi; Azaiez, Jalel; Chen, Zhangxing (John)
    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 investigations. 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. Appropriate 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/reservoir 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 model is that it can be easily downgraded to its equivalent isothermal counterpart. Finally, the developed (isothermal and non-isothermal) simulators have been implemented for a close 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-pressure (HTHP) gas reservoirs have been studied. It has been found that if these complicated effects are not recognized properly, the acquired results particularly via analytical models may be misleading or a test may be designed improperly. The developed non-isothermal coupled wellbore/reservoir simulator allows overcoming all these deficiencies.