There have been extensive efforts to recover oil from the Bakken formation in North Dakota since it was discovered in 1951. However, these efforts were not particularly profitable until the 2000s when horizontal drilling and large, multistage hydraulic fracturing treatment methods were used. The new drilling and completions methods created a substantial increase to production, which escalated throughout recent years and created a demand for better, more efficient completions. One major component of these completions is the base fluid used for hydraulic fracturing treatments. This paper compares hydraulic fracturing treatments of a new, residue-free (res-free) hydraulic fracturing fluid to all other fracturing fluid treatments.The res-free fluid system was presented in 2012 as a premier fracturing fluid and economic alternative to guar-based systems to increase the resultant fracture conductivity. Since 2012, more than 40 wells have been completed in either the Bakken or Three Forks formations of North Dakota using the res-free fracturing fluid. While initial cost savings were realized, the production results from these wells have not been extensively studied. This paper presents the findings of a study comparing production from wells treated with res-free fracturing fluid to wells treated with other hydraulic fracturing fluids.Because the wells completed using the res-free system are widespread throughout North Dakota and belong to several different operators, choosing a specific study area was challenging. To overcome this challenge, a spatial sampling technique was used. Spatial sampling is a method for comparing a large group of wells to their direct offsets. For this study, spatial sampling was applied to compare wells completed using the res-free system to wells completed using other fluids. To normalize general completion methods, only wells completed since the beginning of 2012 are included in this study. Offset wells for this study are those within a 1-mile radius from the center well. The production data for all wells was obtained from public sources. The proppant amount and total fluid volumes were normalized per foot of lateral to minimize variables. Other factors, such as drilling placement, type of proppant, type of fluid, or compartmentalization can affect production; however, these effects are not considered during this study.

The use of sliding sleeve completions has been widely recognized as an efficient and effective means of completing horizontal laterals in unconventional reservoirs for several years. Recently, the focus shifted to optimizing stage spacing and number of stages per lateral. Even with such optimization the entire lateral was not effectively stimulated and drained. In this 15-well pad pilot study, we focused not only on optimizing the design but also on achieving uniform drainage along the lateral. A treatment design using biodegradable diverters to split each stage into two proppant cycles was recommended. The diverter was used on 5 of the 14 wells completed. Total proppant and fluid volumes, as well as proppant and fluid types, were the same on conventionally-treated and diverter-treated wells. Average treating rates and operation procedures were also similar over the entire study group. After stimulation, the wells were turned on with identical chokes and produced similarly. Daily oil, gas, and water rates were monitored over eight months and compared. Production was normalized on a cumulative barrel of oil equivalent (BOE) per foot of lateral basis. Results showed the diverter-treated wells produced 28% more than the conventionally-treated wells at eight months, with the margin increasing. Although all wells were completed on the same pad, at the subsurface level they covered over two miles of structurally variable formation. A multivariate analysis incorporating subsurface, drilling, completion, and production properties was also conducted to determine the most important parameters contributing to hydrocarbon recovery. This study shows that diverters can be incorporated in sliding sleeve completions to lower the total cost per BOE and increase hydrocarbon recovery. This diverter design and technology continues to be implemented in projects with success and positive impacts on production.

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