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.

Research and development of hydraulic fracturing plug materials has shifted to materials that degrade upon exposure to wellbore fluids, thus eliminating the typically necessary post-fracturing millout operations. This paper provides an overview of the field trials and initial commercialization of a dissolvable metal alloy fracturing plug in the Williston Basin. The paper also discusses the alloy’s reaction with wellbore fluids and degradation prediction based on wellbore fluid constituents. During several months of degradable fracturing plug field trials, performance metrics were established, monitored, and analyzed for each stage of the completion process. Tests were conducted using samples of the alloy submerged in actual wellbore fluids from a given field trial to predict wellbore degradation. The test results were correlated to the field trial results, which helped enable prediction of degradation in future field trials. The conventional design and mechanics of the degradable alloy fracturing plug allow it to be set similar to the industry-standard composite plugs because no special tools or processes are necessary. More than 1,500 successful runs have been completed in the Williston Basin alone. Installation performance has been predictable since the field trials began; however, estimating degradation time has been more challenging because fluid-related variables are difficult to control. Degradation can vary significantly, even in similar fluids, because of specific fluid constituents’ effects on the reaction that occurs at the plug-fluid interface. The approach of relating test results to field results helps correlate many of these variables and helps identify specific constituents that affect degradation. Strong production figures allowed an operator to skip post-fracturing treatment millout operations in a few cases, thus saving more than USD 200,000 and several days of millout operations in one particular case. Additional field results and tests should help predict with a higher degree of certainty whether a well can be put on production after the fracturing treatment. This paper summarizes an approach for establishing performance standards, implementing testing methods, and predicting degradation of a degradable alloy fracturing plug designed to help eliminate post-fracturing treatment interventions altogether.

The Golfo de San Jorge basin, located in central Patagonia, is a multilayer reservoir with complex geology. Because of this, the industry traditionally has relied on conventional swabbing as the most reliable way to determine the production and flow rates of each zone. After the wells are drilled and cased, the potential producing layers are perforated and tested to determine individual zone contribution. The well-testing information is used to select the zones that are plugged, the zones that will produce naturally, and the zones that will be fractured to enhance production. The conventional method of well testing includes setting a retrievable plug below the zone of interest and a retrievable packer just above the zone of interest; this is performed with a conventional completion rig using jointed pipe. Next, the rig crew performs necessary swabbing until the produced fluids indicate the type of fluids in the formation and the production capacity. The zones to be fractured are isolated by a retrievable plug and packer during the stimulation job. On average, there are 3.15 zones per well that are fractured and 7.6 zones that are tested (swabbed) per well. The completion of these wells takes approximately 10 days because of the number of swabbing tests and fracturing operations performed. This paper documents results of the field trials performed with a new type of straddle-packer system introduced to reduce the time required to complete a well. This straddle-packer system has the capability to perform well tests and fracture treatments without pulling out of the well. In fact, the operator can swab test a zone or all of the zones, proceed with the fracture treatments of selected zones, and then retest the treated zones, all without pulling out of the well. This technology has proven that it can save a substantial amount of time in the completion and testing phases in the Golfo de San Jorge Basin. This straddle-packer system is a product of a technology-collaboration agreement between the operating company and the service company. This innovative agreement was implemented to have a systematic way to convert ideas into new products and services needed to raise the productivity, increase operating efficiencies, improve safety, and to reduce the lifting cost of the operating company. Background The Cerro Dragon Field is located in the Golfo de San Jorge basin, in the provinces of Chubut and Santa Cruz, Argentina (Fig. 1). It has an area of 3480 km2 and has been exploited since 1958 with approximately 4,000 wells drilled to date. The Golfo de San Jorge basin is a Mesozoic extensional basin filled with Jurasic, Lacustrian, and Cretaceous fluvial deposits with tertiary compression and wrenching superimposed on earlier extensional features. There are about 30 producing structures, each containing 20 to 50 separate reservoir horizons of 4- to 26-ft thickness. Within many of the structures, there is a high degree of fault-induced compartmentalization. In total, there are more than 9,000 separate, highly heterogeneous reservoir units.1 After the well is drilled, the drilling rig is used to run the 5.5-in. casing and, after the casing is cemented in place, the drilling rig moves out. The wireline service company runs a cement-bond log to determine zonal isolation and, after that, the completion rig moves in to test and complete the well. If the zonal isolation is adequate, then all the potential producing zones are perforated with conventional wireline-casing guns.