Abstract

Optimization of unconventional oil and gas assets requires simultaneous consideration of fracturing and porous media flow phenomena. Recent work has demonstrated that a fully coupled fracturing and flow modeling workflow has been used for several recent applications (McClure et al., 2023; Fowler et al., 2023, Pearson et al., 2022). By coupling fracturing and production physics, solutions implicitly reconcile the impact of fracturing designs on depletion results (e.g. – as well spacing is decreased the increased stress shadowing will impact fracture geometries, which in turn, impacts the productivity of the wells). In order to optimize fracturing design for upcoming wells, a coupled model was constructed, calibrated, and used in an optimization workflow.

For this project, a Bakken model was constructed and calibrated to ISIPs, sealed-wellbore pressure monitoring results, bottom hole pressure gauges, and production results from two generations of wells by changing bulk permeability, relative permeability, stress, horizontal toughness, vertical toughness, effective tensile strength, pressure dependent permeability, and time dependent conductivity to match observations of fracture geometry, treating pressure, and three-phase production.

Optimization constraints were set to ensure that all scenarios fell within operational and capital constraints. The optimization was performed in three iterations. The first iteration of scenarios randomly sampled the possible parameter space. Subsequent iterations sampled from parameter-regions that exhibited the highest objective values.

Optimization results demonstrate that there is design optionality. The optimal development design and strategy is a function of the objective function. The biggest parameter driving financial performance is cluster spacing and well spacing. When drilling at closer well spacing there is an improvement in Net Present Value (NPV) per unit at the expense of profitability index (DPI) − all calculated with a 10% discount rate. Fewer wells per drilling section unit increases the DPI, however, comes at a cost to NPV. The optimization workflow delineates the distinct options available to maximize performance.