As field development in the Williston Basin in North Dakota matures, understanding well spacing interaction between Bakken and Three Forks wells is becoming essential for production optimization. Numerous operators are developing the Middle Bakken and between one and four benches of the Three Forks formation with 24 or more horizontal wells per 1,280 acre (two section) production unit. Well spacings are being tested down to 660ft, for single formations and 330ft for adjacent formations.
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 affect oil production in the Middle Bakken wells and illuminates the fact that the Middle Bakken and Three Forks are a complex and intertwined production system.
Well stimulated reservoir volumes can be estimated with microseismic data using a statistical " density contour" approach as an independent indication of horizontal well interaction. Analytic techniques can combine geologic and engineering information in a multi-variate analysis to isolate the impact of individual parameters on well performance. By comprehending the combined influence of well location and engineering decisions, insights are gained into the limits of well proximity for controlling well interaction and optimizing well recovery factors.
Well completions are seen to routinely communicate with wells spaced 1,500ft or farther away, within the same formation. Similarly, wells in adjacent formations, such as the Middle Bakken and 1st Three Forks bench, are also seen to communicate during hydraulic fracturing at distances of 750ft and more. However, well production interference appears to be minimal at a spacing of 1,200ft, within the same formation, and increases approximately linearly with smaller spacings. Recovery factor efficiency and individual well economics support well spacings of 600ft for Bakken and Three Forks benches and ½ or 300ft spacing for staggered well patterns across adjacent formations.