Unconventional/complex reservoirs

Integrated Work Flow Delivers Precise Properties Input for Unconventional Simulation

This paper presents an integrated work flow to model mechanical properties at sufficiently high resolution to honor accurately rock fabric and its effects on height and complexity and, thus, production.

Comparison of standard (Workflow Step 2; panel P5.1) and high resolution joint (Workflow Step 4; panel P5.2) petrophysical outputs
Comparison of standard (Workflow Step 2; panel P5.1) and high resolution joint (Workflow Step 4; panel P5.2) petrophysical outputs with static and dynamic borehole resistivity image (panel P5.3) shown for reference.

To simulate the performance of unconventional wells effectively, incorporating sufficient geological complexity is essential to allow for realistic variability in the petrophysical and mechanical properties controlling the productivity of the effective stimulated rock volume (ESRV). The complete paper presents an integrated work flow to model mechanical properties at sufficiently high resolution (centimeter scale) to accurately honor rock fabric and its height and complexity effects on hydraulic fracturing and, therefore, on production. Once upscaled, outputs of this work flow enable a more-realistic borehole view of reservoir quality, fluid-flow units, and geomechanical stratigraphy, all information key to optimal asset development.

Introduction

Simulating hydraulic fractures with pre-existing natural mechanical discontinuities remains an important challenge. In most cases, the trend is to include more details in the simulations and apply more computational power to solve the problem. While these complex numerical simulations allow simultaneous interaction between multiple phenomena, the validity of the predicted hydraulic fractures, and thus ESRV productivity, may be questionable if inputs to the hydraulic-fracturing and production models do not capture the effective fine-scale complexity of the formation properties, namely the minimum in-situ horizontal stress contrast between layers, the changing layer properties, and the mechanical and flow properties of the interfaces.

The complete paper presents a seven-step work flow wherein core poroelastic anisotropies derived from quantitative mineralogy and well-established micromechanical theory are integrated into a high-vertical-resolution multiphysics petrophysical model able to capture the centimeter-scale level of heterogeneity observed from cores.

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