A Transient Analytical Model for Predicting Wellbore/Reservoir Temperature and Stresses during Drilling with Fluid Circulation

Abstract

Accurate characterization of heat transfer in a wellbore during drilling, which includes fluid circulation, is important for wellbore stability analysis. In this work, a pseudo-3D model is developed to simultaneously calculate the heat exchange between the flowing fluid and the surrounding media (drill pipe and rock formation) and the in-plane thermoelastic stresses. The cold drilling fluid descends through the drill pipe at constant injection rates and returns to the ground surface via the annulus. The fluid circulation will decrease the wellbore bottom temperature and reduce the near-wellbore high compressive stress, potentially leading to tensile fracturing of the well. The governing equations for the coupled heat transfer stress problem are formulated to ensure that the most important parameters are taken into account. The wellbore is subject to a non-hydrostatic in situ far-field stress field. In modeling heat exchange between fluid and surrounding media, the heat transfer coefficients are dependent on fluid properties and flow behavior. Analytical solutions in the Laplace space are obtained for the temperatures of the fluid in both the drill pipe and annulus and for the temperature and stress changes in the formation. The numerical results in the time domain are obtained by using an efficient inversion approach. In particular, the near-well stresses are compared for the cases with fixed and time-dependent cooling wellbore conditions. This comparison indicates that the using a fixed temperature wellbore conditions may over-estimate or under-estimate the bottom-hole stress change, potentially leading to wellbore stability problems.

New wellbore temperature control design for preventing failure and poor performance of logging tools in high pressure – high temperature wells

“… Wu et al (2018) stated as follows: (i) during drilling, the temperature of the fluid entering the drill pipe should be specified and the temperature of fluids in the drill pipe and the annulus should be same at the bottom-hole. (ii) At the wall of the wellbore, the heat flux from the formation is equal to the heat flux into the wellbore Where, wellbore radius, formation temperature, temperature of fluid in the annulus, thermal conductivity of the formation.…”

Modelling of deep wells thermal modes

“…Changes in liquid temperature along the borehole may affect the stability of the well walls. The effect of heat-exchange on the stress state of the well walls is considered in (Wu et al, 2017). The mathematical model and calculation method for determining the temperature distribution along the borehole of production wells of complex structures are presented in works (Yang, Li, Deng, Meng, & Li, 2015;Sui, Horpestad, & Wiktorski, 2018), computer modeling of hydrodynamic and thermal processes in the located near a face well was performed in works (Gorman, Abraham, & Sparrow, 2014;Dreus & Lysenko, 2016).…”

An analytical model for heat extraction through multi-link fractures of the enhanced geothermal system

“…To eliminate the variate of the time, the Laplace transform (Wu et al 2014(Wu et al , 2018 is used from Eq. (1) to Eq.…”