Laboratory Testing and Numerical Modelling of Fracture Propagation from Deviated Wells in Poorly Consolidated Formations

Abstract

This paper presents the results of an integrated laboratory and numerical modelling study on the effect of wellbore deviation and wellbore azimuth on fracture propagation in poorly consolidated sandstone formations. The goal of this project was to develop an understanding of how fractures would transition from single planar fractures to non-planar transverse fractures for fields in the deep-water Gulf of Mexico.The foundation of this work was over 40 fracturing laboratory tests to measure fracture propagation geometries for a range of well deviations, differential horizontal stresses and rock strength. The samples tested were from three outcrops with unconfined compressive strength (UCS) values ranging from 300 -1000 psi. For boreholes having low deviation angles and small differential stresses a vertical single planar fracture was created, aligned with the wellbore, as expected. As the well trajectory and stress contrast increased the fractures became more complex, with transverse turning fractures no-longer aligned with the wellbore.These laboratory results were used to develop and calibrate a new fully-3D finite element model that predicts non-planar fracture growth. The model matches the details of the laboratory tests, including the transition from planar vertical to nonplanar transverse fractures as the well deviation, azimuth and stress differentials increase. After initial model development and calibration was complete a model of a complex case was run before showing any experimental results to the modellers. The model successfully predicted the transverse non-planar results found in the laboratory; this gave us increased confidence in the model as a predictive tool. This work has now been applied with excellent success to four deepwater fields. We have recommended changes in maximum well deviations, performed post-job analyses on wells that had high deviations, and have increased our understanding of the impact of layered formations on fracture growth in these fields.

A Theoretical Model for Hydraulic Fracturing through Two Symmetric Radial Perforations Emanating from A Borehole

“…As the value of K II /K I becomes large enough, the shear sliding becomes the dominant mode of the fracture growth. us, according to the proposed theoretical model, for the model shown in Figure 1(a), the fracture will twist more during its growth under higher stress anisotropy coefficient conditions, which is same as the experimental results obtained by Ispas et al [35]. is is what hydraulic fracturing engineers have been trying to alleviate or avoid.…”

Coupled discrete element modeling of fluid injection into dense granular media

“…[10] Laboratory experiments of fluid injection under triaxial conditions have been conducted in sand and in mixtures of sand and silica flour [Khodaverdian and McElfresh, 2000;Chang, 2004;Bohloli and de Pater, 2006;Bezuijen et al, 2006;Dong and de Pater, 2008;Zhou et al, 2010;Golovin et al, 2010Golovin et al, , 2011Germanovich et al, 2012;Hurt and Germanovich, 2012;Ispas et al, 2012] and in clay [Murdoch, 1993b[Murdoch, , 1993cBolton et al, 1994;Au et al, 2003;Soga et al, 2004]. While the experiments in clay have mostly produced opening mode tensile fractures, the phenomena in sand are much more complex due to the coupling of fluid infiltration and grain displacements.…”

Interaction between hydraulic fractures and natural fractures: current status and prospective directions

“…The auxiliary HF will likely propagate the tip of the shear-activated NF plane, which tends to create new interconnected fractures. Transverse fractures are likely to be created due to shear failure in the Marcellus shale (Aimene and Nairn 2014), and in weak and poorly consolidated sandstones (Ispas et al 2012).…”