Abstract

The application of multi-stage fracturing in the Bakken Formation, Elm Coulee Field, Montana of the Williston Basin has been applied using hydraulic packers for zonal isolation with ball actuated frac 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 frac (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 reserve estimation, interference, drainage and well spacing require an understanding of the created fracture geometry from multi-stage 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 horizontal wells 2,000 feet apart with a horizontal well in between. The following topics will be discussed as part of this paper:

  1. Success and failure achieving proper stage isolation, diversion and fracture stimulation coverage using hydraulic packers for zonal isolation with ball actuated frac 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 utilization 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, Montana, Williston Basin. Detailed reservoir engineering led to optimized multi-stage fracturing that was applied using hydraulic packers for zonal isolation with ball actuated frac 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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