The horizontal Bakken/Three Forks play of the Williston basin has a long standing history of recompletion dating back to the late 1980s. While rapid evolution of horizontal completion design has allowed expansive Bakken/Three Forks unconventional acreage positions to reach economically viable levels, existing legacy completions have historically been difficult to invigorate to modern productivity expectations. Although recompletion is nothing new to the oil and gas industry, the techniques applied are highly variable and historically may carry disappointing and unpredictable results. As a need for better understanding of principle well development continues to evolve, so do better techniques in legacy well recompletion tactics to enhance both developed and undeveloped assets. Within the Bakken/Three Forks play, legacy development drilling and completion tactics are vast with significant productivity variances. Industry mindshare often incorrectly groups all recompletion methods into a single category. Differences in technical application, and associated value added per input cost, require subcategorization of recompletions to improve well productivity. A holistic identification process is required to appropriately match the service intensity associated with refracturing, reentry, or remediation to project costs and asset potential. The focus of this study is to compare and evaluate the production results attained from recompletions in the discrete subcategories of well refracturing, reentry, and remediation. Empirical datasets will be presented to define the project inputs and production value capture associated with each recompletion type. By integrating these workflows, enhanced recompletion design and execution can create value at previously unattainable commodity price levels. A comprehensive completion and production database of horizontal Bakken/Three Forks wells dating from 1987 to present has been developed to facilitate recompletion selection, design, and predictive production forecasting. Proprietary software that automates production analytics, combined with manual canvassing of over 10,000 wells, has provided an innovative method to cross-examine the Bakken/Three Forks play. By combining a multivariate assessment with probabilistic results, novel recompletion propositions can be successfully matched to project needs.

Recent developments in completion techniques and stimulation efficiency have allowed many unconventional resource plays to reach economically viable levels. The Bakken/Three Forks play of the Williston basin has rapidly evolved during recent years, and its predominantly successful completion techniques continue to emerge as programs are tailored to geographic areas. As completion intensity increases to facilitate higher early time production returns, so does the need for the critical analysis of production decline rates to meet economic targets.The application of decline curve analysis in unconventional reservoirs, such as the Bakken/Three Forks play in North Dakota, is often problematic because of very long periods of transient flow. This has caused the development of various decline curve relations outside the conventional Arp's equations in an attempt to better explain the transient flow period. Additionally, it has sparked interest in quantifying the uncertainty associated with production and the estimated ultimate recovery (EUR) from these various techniques.The Bakken/Three Forks system is exploited using a large variation of publically reported completion techniques throughout a significant geographic area. Because of the uncertainty in assessing the performance of unconventional wells and the multitude of variables that could affect their production, it is often difficult to determine dominant influencing parameters of completion design. Efficiently implementing optimal completion techniques, provided there is high variability within a continuous horizontal target lithology, is critical because of the large geographic extent of the Williston basin.The focus of this study is to evaluate the completion efficiency of individual wells using decline curve analysis and to quantify uncertainty using this performance metric. A comprehensive completions database of the Bakken/Three Forks play is used to evaluate the expected costs and benefits of various completion designs used throughout the basin. This paper provides examples of stimulation methods optimized to specific regions of the Bakken/Three Forks system using this methodology. Overview of DatabaseTo document the variability in completion design and production throughout the Williston basin Bakken/Three Forks system, a comprehensive database of publically reported completion and production data has been compiled using the North Dakota Industrial Commissions (NDIC) website. In addition to legal information (well name and number, completion date, etc.), the latitude and longitude, target formation, maximum rate, stimulation zones, total treatment fluid, total proppant, completion system, annular isolation, stimulation fluid, primary proppant, and initial production (IP) test choke were recorded. For each well reported, production data was also recorded at various time steps. Because the NDIC reports the number of production days each month, down days were removed from the production data, and linear interpolation was used to obtain production values at 30-da...

Shale and unconventional reservoir wells require multiple completion options be available so that the best one can be selected to maximize the stimulation influence potential, enable efficient operations, and increase production potential. Shale and unconventional reservoir continuous resource wells are typically drilled horizontally with the completion system run in the lateral section of the wellbore. The completion design must enable the hydraulic fracturing of multiple discreet treatment zones in the target interval to help ensure economical production. Traditionally, unconventional reservoir wells have been completed using a plug and perforate methodology. This completion uses wireline intervention to set composite fracturing plugs for stage isolation and to perforate individual stages. Due to inefficiencies with this type of completion design, single entry fracturing sleeve systems (SE FSS) completions have gained acceptance. SE FSS offer a single entry point per stage and remove the need for wireline intervention thereby increasing completion efficiency. Recently, multi-entry fracturing sleeve systems (ME FSS) completions have been deployed in unconventional reservoir stimulation operations. ME FSS completions also do not require wireline intervention, and allow for multiple entry points per stage to be simultaneously stimulated. Even though it is optimal for unconventional reservoir development to have several completion alternatives, evaluation of the best method can be challenging. This paper will evaluate the three dominant and currently applied completion methods by comparing wells in the Middle Bakken continuous resource play which have utilized all identified systems. The paper will discuss each of the three completion methods (Plug-and-Perforate, SE FSS, ME FSS), the completion design, and fracturing operations that are executed. The paper will then illustrate production results from using all three of the completion methods. This data will be drawn from similar well designs for comparison purposes. Assessment of viability and production efficiency of ME FSS completions against other completion methods is the primary focus. Results will be presented based on production outputs obtained after a qualified 180 day period. Conclusions will also highlight the potential efficiency gains of a ME FSS completion versus traditional methods.