Transient Temperature Modeling For Wellbore Fluid Under Static and Dynamic Conditions

Abstract

Modeling flowing wellbore fluid transient temperature is important in many petroleum engineering problems, including, pressure transient testing, flow assurance and wellbore integrity during production, preservation of drilling equipment integrity for geothermal wells and prediction of injection fluid temperatures.

In this thesis, development and usage of three models for transient fluid temperature are presented. Two models predict transient temperature of flowing fluid under separate flow configurations and one is for a static fluid column. Additionally, an improvement to an existing transient temperature solution is given.

The transient rate model predicts the transient temperature when a flow rate, during production, is changed from some initial value to a new one. This model is particularly useful for pressure transient tests involving multiple disparate constant flow rates where bottomhole pressure has to be calculated from the wellhead pressure. Dependence of fluid density on variable temperature during the test necessitates that effects of unsteady temperature changes are taken into account for accurate calculation of downhole pressure.

The single rate injection model predicts transient temperature of wellbore fluids during injection operations. This model can help in design of acidizing treatments by allowing users to calculate the time required to cool down the well with water pre-flush. This model can also be used for calculation of depth of effectiveness of wax removal treatment, in case of hot oil injection.

Very high temperatures during drilling operations can deteriorate mud rheological properties. The conduction model lets the user calculate the time window available for taking corrective actions after an accidental cessation of mud circulation occurs.

Method of Laplace transform enabled solution of a temperature distribution equation to create the transient rate model and the injection model. Conduction model was developed by solving the transient heat conduction equation for a multilayer cylinder with mud in annulus and tubing analogous to two layers of the cylinder. All solutions were implemented using conventional spreadsheet software with rudimentary programming.