Chen, ZR & Jeffrey, RG 2008, 'Surface Weight Change Effect on Tilt Field and Hydraulic Fracture Inversion Accuracy', in Y Potvin, J Carter, A Dyskin & R Jeffrey (eds), Proceedings of the First Southern Hemisphere International Rock Mechanics Symposium
, Australian Centre for Geomechanics, Perth, pp. 333-346.
This paper studies the effect of changes in weight of objects at a fracturing site, such as produced by emptying of frac tanks and proppant trucks or bulk storage silos during a hydraulic fracturing treatment, on the tilt field and tiltmeter measurements. We consider when these effects need to be taken into account to obtain an accurate analysis for fracture inversion. The hydraulic fracture is represented in the forward model as an opening mode, rectangular dislocation within a homogeneous, isotropic linear-elastic semi-infinite medium, while the change in the weight of the frac tanks or proppant storage vessel during the fracturing treatment is modelled by a normal concentrated load acting on the surface or by a uniform pressure over a circular or rectangular area on the plane surface boundary of the elastic semi-infinite medium. Analytical expressions for the tilt field are obtained, and some new results are observed. The tilt field, induced by weight variation of objects on the surface, is analysed in detail. Furthermore, synthetic examples are presented to investigate its effect on the inversion accuracy to obtain fracture orientation and centre offset.