The objective of this paper is to demonstrate XTO's approach to optimizing well spacing and stacking in the Bakken through an integrated data acquisition program that directly measures wetted fracture geometries and reservoir drainage. The paper will discuss previous development strategy, uncertainties in development plans, and how the proposed pilot program will reduce the uncertainties. It will include pilot program design, utilized diagnostic technologies, data analyses and interpretation, and finally the implication on future development in the Bakken.
Two dedicated monitor wells were drilled around a single Middle Bakken producer to measure wetted and conductive fracture geometries. Trajectories of the two monitor wells, one in the Middle Bakken and one directly below the producer in the Three Forks, were strategically designed to intersect hydraulic fractures at varying distances from the producer. All three wells were instrumented with external fiber optic cables and arrays of pressure gauges. During stimulation, fiber and pressure gauges were monitored to obtain cluster efficiency and wetted fracture geometries. Proppant transport distance was estimated by injecting radioactive proppant tracers in the producer and logging the monitor wells. Conductive fracture geometries or drainage dimensions around the producer were delineated by pressure array readings during production. Acquired diagnostic data was used to calibrate fracturing and reservoir simulation models for future completion optimization.
Fiber monitoring during stimulation revealed that Bakken completion design yielded high cluster efficiency, and that wetted fractures propagated far from the producer and through all benches between the Three Forks and Lodgepole. Even though RA tracers indicated large proppant transport distance, pressure readings from the gauge arrays indicated that conductive fracture dimensions are only fractions of the measured wetted fracture dimensions. In addition, data also showed that the Middle Bakken producer was effectively draining the Three Forks. With the current completion design, results from the pilot test supported larger well spacing for Middle Bakken and Three Forks co-development. A calibrated simulation model also suggested that water usage may be reduced while maintaining similar well performance.
This work demonstrated that dedicated slant monitor wells with integrated diagnostic instrumentations can accelerate field development optimization by directly measuring hydraulic fracture dimensions. Data from the project methodically demonstrated the fundamental relationship between cluster efficiency, wetted fractures, propped fractures and conductive fractures that contribute to production. Measurements from the pilot were combined with integrated fracture and reservoir modeling tools and resulted in significant capex reduction by allowing larger well spacing and reduced fresh water usage in XTO's Bakken acreage.
