An Analytic Approach to Optimizing Well Spacing in the Bakken/Three Forks Oil Play

Rodriguez, Camilo; Roth, Murray¹; and Roth, Michael
¹[email protected]

DESCRIPTION:

As field development in the Williston Basin in North Dakota moves more towards in-fill drilling, understanding optimal well spacing and the complex interaction between wells in the Middle Bakken and Three Forks formations will be crucial for implementing a successful drilling program. In order to isolate the effect of well spacing on well performance; variations in completions techniques and changes in geology for the producing wells must be comprehended using multi-variate, Reservoir Analytics.

Investigation of oil and water production curves indicates strong evidence of frac communication between neighboring Middle Bakken, as well as with adjacent Three Forks wells where treatment fluid from the completed well is being produced back by the adjacent Middle Bakken well. This communication between zones has been seen to effect oil production in the Middle Bakken wells and illuminates that the Middle Bakken and Three Forks are a complex and intertwined production system.

Well stimulated reservoir volumes are estimated with microseismic data using a statistical "density contour" approach. Combining the information derived from multi-variate, well spacing analysis, decline curve investigation, and microseismic interpretation, optimal well spacing practices across the Williston Basin can be determined.

APPLICATIONS:

The techniques outlined in this paper can be applied in support of field development in any unconventional reservoir. Understanding the effect of well spacing on production is crucial for optimizing in-fill drilling programs. Incorporating economics into the model, potential in-fill locations can be graded based on projected profitability.

RESULTS AND CONCLUSIONS:

Multi-variate analysis of well spacing performed in the context of engineering, completions, and geology, indicates that as Middle Bakken well spacing is increased from 500ft to 1,500ft, the oil production improves, but with no further improvement beyond 1,500ft spacing. Decline curves show that within 1,500ft spacing, fracture fluid communicates between Middle Bakken wells. Microseismic data also confirms that 1,500ft spacing limits the overlap of stimulated reservoir volumes for neighboring wells.

Decline curves show the communication between Middle Bakken and Three Forks wells. Evidence suggests that Three Forks wells may provide a "re-frac" effect for Middle Bakken wells that results in a prolonged improvement in Middle Bakken well performance.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013