Development Optimization of Horizontal Wellbores Using Lamé Elastic Constants From 3-D Seismic

Abstract

Technological advancements in horizontal drilling and fracture stimulation of tight oil formations have resulted in the resurgence of the century-old mature Permian Basin. Current development strategies typically involve a “harvesting” approach whereby multi-well pads are used to drill stacked horizontal layers within the Spraberry and Wolfcamp formations in a repeated sequence, implementing identical geometric stage placement. As such, these methods assume similar rock properties and stress states along horizontal wellbores which can be problematic. This can result in undesirable effects such as well underperformance, pressure sinks from nearby depletion, and well bashing resulting from unintentional stimulation and communication of nearby producing wells. In hopes of mitigating such quandaries, more operators are increasingly implementing development strategies that encompass evolving subsurface technology that integrates multi-domain data types including geology and stratigraphy, geomechanics, petrophysics, reservoir engineering, and 3D seismic data calibrated to rock physics.

This method presents an empirical approach based on the integration of said multi-domain data types calibrated to AVO seismic data inverted for compressional wave velocity (Vp), and shear wave velocity (Vs), but expressed in terms of Lamé elastic constants defined by lambda (λ) or incompressibility, and mu (µ) equivalent to shear modulus. For geomechanics, Lambda and mu define Hooke’s law relating stress to strain which intrinsically defines the fracability of brittle and ductile rocks, and can also estimate closure stress in terms of elastic moduli estimated from seismic. Moreover, the ratio of λ/µ (Goodway, 1997) shows increased sensitivity to rock property variations relative to other elastic constants including Poisson’s ratio, and therefore represents a more accurate estimate of seismic lithology.

Lamé elastic constants successfully characterized reservoir and completion quality along laterals within the Spraberry and Wolfcamp formations. Lambda-rho and Mu-rho (LMR) crossplots, derived from conditioned log data and calibrated to rock physics templates, were used to guide seismic interpretation to identify rock property heterogeneity along wellbores. Vertical and horizontal pseudo seismic logs extrapolated from the elastic inversion volumes were used to constrain 1D mechanical earth models for calibration of fracture modeling, and for optimization of completion parameters.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018