Abstract
Traditional modeling approaches for hydraulic stimulation treatments typically make the assumption that the formation can be modeled as a linear elastic material under static equilibrium. As such, all information regarding the transient response of the formation is neglected. However, during a hydraulic stimulation treatment, transient geomechanics forces are exerted on the formation, which modify the stress landscape near the wellbore and fracture planes. In regions where the horizontal stress anisotropy is less than 25%, the potential for a temporary reversal in the minimum stress direction exists. During this brief time window, a secondary hydraulic fracture can be created in a completely different direction, thus providing direct connectivity to previously unattainable locations in the formation. This paper presents a computational validation of this process using a unique transient 3D computational geomechanic fracture simulation. This new stimulation method enhances current standards in hydraulic fracturing by requiring an understanding of the transient geomechanic response in the treatment area.
1. INTRODUCTION
During a hydraulic stimulation treatment, geomechanic forces are exerted on the formation, which temporarily modify the stress landscape near the wellbore [1, 2]. This phenomenon is often referred to as stress shadowing, and is traditionally considered a negative byproduct of hydraulic fracturing treatments. The increased compressive stress caused by the first fracture acts to naturally divert subsequent fractures, and can significantly limit the fracture growth [3]. Under certain circumstances, the stress shadowing can create a full reversal of the local minimum and maximum stress directions (Fig. 1), causing the next fracture to propagate perpendicular to the original in-situ maximum stress direction [4]. Several modeling efforts, similar to those conducted by Morrill and Miskimins [4], have been undertaken to better understand the sensitivity of various formation and treatment parameters on the size of the stress shadowed region. The goal of these studies was to predict the extent of the effected zone for prescribing optimal fracture spacing along the lateral section of a horizontal well to prevent fracture interference.
