Rapid Field-Scale Well Spacing Optimization in Tight and Shale Oil Reservoirs Using Fast Marching Method
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Copyright 2018, Unconventional Resources Technology Conference (URTeC). An immediate and pressing need in the development of unconventional reservoirs is an innovative workflow that facilitates fast optimization of well placement. The optimal well placement design must ensure minimal interference between wells while maximizing the recovery/NPV. However, due to highly uncertain and poorly understood complex fracture geometries, optimal well spacing designs based on classical analytical techniques can be unreliable. We propose a rapid workflow to optimize well placement in unconventional reservoirs using the Fast Marching Method (FMM). Our approach is to partition the reservoir model into independent sub-domains associated with individual wells based on the Diffusive Time of Flight (DTOF) computed as solution to the Eikonal equation using the FMM. Multiphase production rates are then computed for each well by utilizing the DTOF as spatial coordinate to reduce the full 3-D numerical model to 1-D equivalent models resulting in orders of magnitude speed up in computation time. The computational efficiency of our approach enables extensive simulation runs to determine the point of diminishing return for additional well placement to obtain the optimal well spacing. We illustrate the power and utility of our optimization workflow using synthetic and field-scale examples with multiple multi-stage hydraulically fractured wells. First, we demonstrate the reliability of our technique by confirming good rank correlation between our FMM-based simulation workflow and 3-D finite difference simulation. Next we apply our optimization strategy to obtain the optimal well spacing while accounting for uncertainties in complex fracture geometries and conductivities. Finally, we show the robustness of our well spacing optimization workflow with an application to a shale oil reservoir in the Eagle Ford. A unique and distinctive feature of our workflow is the computational efficiency that results from the significant reduction in simulation complexity through FMM-based 1D transformation. This enables rapid evaluation of well placement designs for large field models using an exhaustive search method which can be computationally prohibitive using classical numerical simulation techniques.
author list (cited authors)
Iino, A., Onishi, T., Olalotiti-Lawal, F., & Datta-Gupta, A.