One of the most important challenges in the Jonah Field in Sublette County, Wyoming, is to obtain effective fracture-height coverage over the entire 2,800+ ft Lance formation. The Lance formation in Jonah Field is composed of a stacked sequence of 20 to 50 fluvial channel sands interbedded with associated overbank siltstone and floodplain shale deposits. Within this interval, the net-to-gross ratio varies from 25 to 40%. Sandstone bodies occur as individual 10- to 25-ft thick channels and stacked-channel sequences greater than 200 ft in some cases.
Tiltmeter and microseismic fracture mapping was conducted on hundreds of propped-fracture treatments in the Jonah Field. These direct height-growth measurements helped to obtain an understanding about the effectiveness of shale barriers. It was found that a standard triple-combo log suite could be used to identify shale barriers for fracture growth.
A calibrated fracture model was developed for the Jonah Field that ties the log analysis to the fracture-growth behavior that was mapped using direct fracture-mapping technologies and to the net-pressure response measured during propped fracture treatments. These improvements in predictive modeling capabilities have lead to better insight into fracture growth behavior in the Lance formation.
A 3D fracture-growth model was modified to determine perforation strategy and fracture-treatment schedules to obtain effective coverage of the Lance formation in new Jonah wells in a semi-automated process. As a result, the entire process for fracture design can now be performed in an integrated software package.