Multistage fracturing in the Bakken formation, Elm Coulee field, Williston basin, Montana, has been performed using hydraulic packers for zonal isolation with ball-actuated fracture sleeves to improve performance of horizontal wells. Optimizing development drilling and fracture-treatment designs for horizontal wells requires an estimation of the fracture geometry (azimuth, height, and half-length, with respect to lateral orientation). A fracture treatment designed under the assumption of a longitudinal fracture (along the length of the borehole) will be entirely inadequate if the actual fracture propagates in a transverse orientation (perpendicular to the length of the borehole) and vice versa. Recovery factor and reserves estimation, interference, drainage, and well spacing require an understanding of the created fracture geometry from multistage completions.

This paper describes how real-time downhole microseismic monitoring, fracture-treatment pressure interpretation, and subsequent production evaluation were used to better understand the created-fracture geometry, completion staging efficiency, and fracture-stimulation effectiveness in a project with two parallel 4,000-ft middle-Bakken treatment horizontal wells 2,000 ft apart with a horizontal well in between. The following topics will be discussed as part of this paper:

  1. Success and failure in achieving proper stage isolation, diversion, and fracture-stimulation coverage using hydraulic packers for zonal isolation with ball-actuated fracture sleeves in two 4,000-ft laterals.

  2. Fracture azimuth and half-length as related to entry-point spacing and intersections with nearby wells.

  3. Fracture-height growth up into the Lodgepole limestone and down into the Three Forks formation as related to microseismic location uncertainties and use of this information in fracture-model calibration.

  4. Discussion and comparison of the production response for past completion strategies to the current approach, as well as discussion about production interference between horizontal wells.

The integration of fracturing-mechanics studies that began with the initial vertical wells and concluded with current-day horizontal applications in concert with detailed reservoir-engineering evaluations has resulted in significant production improvement in the Bakken formation, Elm Coulee field, Williston basin, Montana. Detailed reservoir engineering led to optimized multistage fracturing that was applied using hydraulic packers for zonal isolation with ball-actuated fracture sleeves to improve performance of horizontal wells. Using a calibrated/customized fracture model that had been developed from evaluation of hundreds of wells in the basin, the fracture-treatment pump schedules were designed to minimize fracture complexity and optimize lateral proppant placement to attempt to create an ideal transverse-fracture geometry within a horizontal well. Microseismic imaging was used to confirm the historical information in the basin, fracture mechanics studies, and customized models relative to the azimuth, height, and half-length with respect to lateral orientation.

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