Fracture nucleation and propagation are controlled by in-situ stresses, fracture treatment design, presence of existing fractures (natural or induced), and geological history. In addition, production driven depletion and offset completions may alter stresses and hence fracture growth. For unconventional oil and gas assets the complexity resulting from the interplay of fracture characteristics, pressure depletion, and stress distribution on well performance remains one of the foremost hurdles in their optimal development, impacting infill well and refracturing programs. To this end, ExxonMobil has undertaken a multi-disciplinary approach that integrates fracture characteristics, reservoir production, and evolution of the stress field to design and optimize developments of unconventional assets. In this approach, fracture modeling and advanced rate transient techniques are employed to constrain fracture geometry and depletion characteristics of existing wells. This knowledge is used in finite element geomechanical modeling (coupling stresses and fluid flow) to predict fracture orientation in nearby wells. In this paper, an integrated methodology is described using case studies for two shale gas pads. The study reveals a strong connection between reservoir depletion behavior and the spatial and temporal distribution of stresses. These models predict that principal stresses are influenced far beyond the drainage area of a horizontal well and hence play a critical role in fracture orientation and performance of neighboring wells. Strategies for manipulating stresses were evaluated to control fracture propagation by injecting, shutting-in, and producing offset wells. Collective interpretation of completion, reservoir depletion and changes in stresses explained varying performances of wells and enabled evaluation of infill potential on the pad. This workflow can be used to develop strategies for (1) optimal infill design, (2) controlling propagation of fractures in new neighboring wells, and (3) refracturing of existing wells.

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Fracture nucleation and propagation are controlled by in-situ stresses, fracture treatment design, presence of existing fractures (natural or induced), and geological history. In addition, production-driven depletion and offset completions may alter stresses and hence the nature of fracture growth. For unconventional oil and gas assets the complexity resulting from the interplay of fracture characteristics, pressure depletion, and stress distribution on well performance remains one of the foremost hurdles in their optimal development, impacting infill well and refracturing programs. ExxonMobil has undertaken a multi-disciplinary approach that integrates fracture characteristics, reservoir production, and stress field evolution to design and optimize the development of unconventional assets. In this approach, fracture modeling and advanced rate transient techniques are employed to constrain fracture geometry and depletion characteristics of existing wells. This knowledge is used in finite element geomechanical modeling (coupling stresses and fluid flow) to predict fracture orientation in nearby wells. In this paper, an integrated methodology is described and applied to a shale gas pad as a case study. The work reveals a strong connection between reservoir depletion and the spatial and temporal distribution of stresses. These models predict that principal stresses are influenced far beyond the drainage area of a horizontal well and hence can play a critical role in fracture orientation and performance of neighboring wells. Strategies for manipulating stresses were evaluated to control fracture propagation by injecting, shutting-in, and producing offset wells. In addition, we present diagnostic data obtained from the pad that demonstrates inter-well connectivity and hydraulic communication within the pad. The workflow presented herein can be used to develop strategies for (1) optimal infill design, (2) controlling propagation of fractures in new neighboring wells, and (3) refracturing of existing wells.

This paper describes the development, validation, and application of new 3D finite element models for a diverse set of oil & gas problems involving fluid-driven fractures. Applications described in the paper includes drilling wellbore integrity / lost returns, drill cuttings disposal, and hydraulic fracture water injection.The models were developed and implemented in a commercially-available finite element (FE) software package. The models include both cohesive elements (mesh conforms to pre-defined fracture orientation) and extended finite elements (fracture geometry evolves independent of the finite element mesh). Advantages and disadvantages of each approach will be described. The models were validated through comparisons with published analytical solutions for extreme values of rock and fluid properties and leak-off conditions (with all realistic physical problems lying within these extremes). A comprehensive suite of large-scale laboratory experiments were also conducted and models were used to replicate conditions and results of these experiments. Larger finite element models were then constructed and used to demonstrate applicability to a broad range of realistic oil & gas problems, including 2D and 3D problems with large length scales and long time scales enabled by high-performance massively parallel computing systems.The models show excellent agreement with published analytical solutions for a broad range of rock and fluid properties and fracturing conditions. The models also show agreement with laboratory experiments for a similar range of conditions. The models scale up from lab to well scales and have shown good applicability for a diverse set of realistic and challenging oil and gas problems.Most hydraulic fracture models fall into the categories of fast-running but with simplified physics or complex physics but computationally impractical for full-scale commercial applications. The models described in this paper have been applied at full commercial time and length scales but also provide for full representation of the complex physics of hydraulic fracturing, as demonstrated by the comprehensive validation with analytical solutions and laboratory experiments.