Accelerating Learning in the Unconventionals Through Integrated Field Experiments

Abstract

Abstract This paper provides an overview of unconventional field experiments that ExxonMobil has conducted in recent years to measure the dimensions of fractures generated in the subsurface. These learnings are combined with production analysis to support and inform development decisions to avoid overcapitalization from suboptimal spacing, stacking, or stimulation choices. Specific field experiments exemplify the importance of experimental design and instrumentation, as well as associated deployment challenges. Highlighted are the benefits of dedicated monitor wells equipped with fiber optics and pressure gauge arrays to interrogate the three-dimensional fracture network. While challenging to execute, this approach provides definitive measurements of the extent and variability of fracture dimensions and depleted rock volume, and requires the integration of downhole measurements, interpretation, and tool automation. Vertical monitor wells are effective in determining the overall height of the created fractures as well as the drainage boundaries of individual benches. Slant monitor wells extend these measurements of fracture density and depletion at varying distances from a stimulated well to enable mapping of the fracture drainage network. Systematic variation of the completion design along the treatment well adjacent to a slant monitor well can be implemented to directly compare the efficacy of treatment design options in the same well. To handle the large amounts of collected data from field experiments, automation of diagnostics workflows and integration of the data in a single tool become imperative. Pressure measurements are integrated with fiber optic measurements to provide a holistic interpretation of the extent and heterogeneity of the stimulated rock volume. Due to their complexity and cost, instrumented slant monitor wells are rarely executed. A summary of multiple field trials are provided here where well designs, deployment, data collection, and integrated analysis were used to aid development planning and optimization.