Date of Award

January 2018

Document Type


Degree Name

Master of Science (MS)


Petroleum Engineering

First Advisor

Mehdi Ostadhassan


The common development plan for operators in the Williston Basin has been to initially drill and complete one well in order to hold a 1280 acre spacing unit. Once acreage is secure across the asset, operators return to each spacing unit and drill infill wells. By the time infill wells are drilled, reservoir depletion from the original (parent) well can be observed within the spacing unit. Reservoir depletion increases the likelihood of existing wells experiencing inter- communication when infill wells are hydraulically fractured. Such inter-well communication, or frac-hits, often have detrimental effects on existing wells. As such, understanding the effect of well timing and spacing on overall spacing unit performance is of critical importance when determining an appropriate development plan.

Rate transient analysis (RTA) is an effective way to quantify the impact of offset frac hits, providing changes in reservoir properties such as stimulated rock volume (SRV) and well productivity. This study used pseudo normalized pressure versus material balance square root of time plots in order to determine the impact of offset frac hits on existing wells. The slope of the superposition time plot is inversely proportional to A_c √(k ) , which offers a good metric for early time well productivity and completion effectiveness. Superposition time plots were created, and a production lookback was performed on 71 operated wells in northern Divide County, North Dakota. Changes observed in reservoir properties and production performance were used to determine appropriate well spacing and infill timing.

In addition, this study conducted a look back economic evaluation for 71 wells and 15 spacing units, using current commodity pricing, to assess the investment efficiencies of each project. Results from rate transient analysis, production analysis, and the economic evolution indicate that 5 – 6 wells is the optimal wells spacing per 1280 acre spacing unit within the study area.