Breakdown overpressure in 3-D poroelastic inclined borehole

Document Type

Conference Proceeding

Publication Date

1-1-2020

Abstract

The breakdown pressure is a critical parameter for planning well test, surge and swab operations and/or stimulation jobs. To predict breakdown pressure, the fluid injection volume, formation permeability as well as the time dependency of fluid pressure build-up inside the well, are some of the parameters needed to consider. In this paper, the breakdown pressure from a finite-length interval in an inclined wellbore is solved in the framework of the coupled theory of poroelasticity. The in-situ stresses are transformed into a local borehole coordinate system as the far-field boundary conditions. The finite length packed interval is subjected to an injection fluid volume coupled with the applied in-situ stresses. A dual Laplace-Fourier transform technique is used to obtain time-dependent stresses and formation pressure build-up. To more realistically reflect the fluid pumping conditions involved in the field stimulation of hydraulic fracturing, a ramp-type flux loading boundary condition at the borehole wall is adopted, and the stresses and fluid pore pressure at the wellbore wall and in the formation are calculated. Numerical analyses carried out for the most common wellbore setting in fracturing operations, i.e., horizontal wells, show that both "fracturing stress" – in this case, the tangential stress – and pore pressure increase as time progresses and/or injection interval length decreases. It becomes clearly necessary to consider the impacts of the ratio of the packed interval length to wellbore radius, fluid pumping conditions, formation permeability, in adition to the coupled poroelastic effects when estimating in-situ breakdown pressures. The developed solutions can be used to generate the desired engineering charts as a generic, novel, and efficient tool in the interpretation and/or design of well test and hydraulic fracturing jobs for vertical, horizontal and inclined boreholes.

Publication Source (Journal or Book title)

International Petroleum Technology Conference 2020, IPTC 2020

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