This February 2011 study compares the production and cost impacts of using energized and non-energized fracturing fluids on unconventional gas wells in the Montney formation. Analysis of roughly 24 to 36 months of gas production show significant benefit can be achieved from energized fracturing fluids and that their use warrants investigation in other unconventional oil and gas plays. There is illustrated potential for significant gas recovery improvement. There is also opportunity to reduce fracturing resources; the most significant of which is water and proppant consumption; there is also opportunity to reduce pumping rate and pressure in some instances. The potential environmental benefit of considerably lowering water consumption is attractive and may, in itself, justify their use. Energized fracturing treatments can cost more; however, the benefits are shown to far outweigh the incremental costs. The opportunity exists to improve unconventional well fracturing effectiveness and to reduce the resources used in those treatments by including nitrogen or carbon dioxide in the fracturing fluid. Based on the comparative assessment completed on the subject Montney wells in the Dawson Area of N.E. British Columbia, the use of energized fluids is shown to generate significantly improved well performance over those wells fractured with non-energized fluids. On average each well stimulated with energized fluids is forecast to potentially recover between 1.1 to 2.2 times as much gas as non-energized fracturing treatments the Study Areas 1 and 3 respectively. Area 1 Study compared the performance of Slick Water against Nitrified Slick Water and CO2 Foam fracturing treatments. The production analysis predicts an 11% incremental recovery improvement of 0.29 Bcf by using energized fluids. Though the treatment costs for the energized fracture treatments were seen to be higher, the value of this incremental recovery outweighs the additional cost with no incremental risk. Of note was the opportunity to reduce the fracturing fluid liquid volumes by over half with using CO2 Foam treatments rather than Slick Water. This shows the opportunity to improve production while also minimizing environmental impact. At marginal gas prices of $4.00/Mcf, the value of this incremental recovery approaches $1.4 MM from an incremental fracture cost investment of $500,000. Area 3 Study compared the performance of Gelled Frac Oil against CO2 Foam fracturing treatments. The production analysis showed a 124% incremental recovery improvement of 3.75 Bcf by using energized fluid fracturing treatments. At marginal gas prices of $4.00/Mcf, the value of this incremental recovery approaches $14.8 MM, from an incremental fracture cost investment of $400,000.
Recently, there has been discussion of the need to advance hydraulic fracturing technology from the current ‘operational effectiveness’ mode of high-rate slickwater fracture designs, to a ‘fracture effectiveness’ mode provided by optimizing designs to achieve higher recoveries and better economics. This case study shows how advanced fracture fluid system designs have increased fracture effectiveness in an area of the Montney unconventional gas play. The study focused on fifty multi-stage fractured horizontal wells in the dry gas area of the Heritage Montney Field in British Columbia, Canada. These wells were stimulated by different operators with a number of different fracturing techniques, fluid systems, etc. Wells were selected such that a sufficient variety of completion techniques were represented, and there was over 18 months of production history. A thorough review of the geology and petrophysical data within the area was undertaken in order to develop individual well descriptions for use in the production analysis (Rate Transient Analysis). Wells were history matched by varying reservoir permeability and fracture treatment properties. The results demonstrate that fracture effectiveness is a function of the fracture type and has a large effect on well productivity and economics. This case study shows there is value in optimizing fracture designs through look-back studies, and that there is a need to focus on more effective fracture treatment designs in unconventional gas development. The results of the study show the importance of fracture fluid selection as well as both effective fracture half-length and fracture conductivity in maximizing the economic returns in this area of the Montney.
A major issue with determining the effectiveness of different completion strategies is reservoir heterogeneitywhich is to be expected with most unconventional resource plays. Two horizontal wells separated by 400 m or less lateraly, completed and stimulated identically may result in one well peforming significantly better than the other, with significantly higher estimated ultimate recovery (EUR). Hence the statistical approach to the problemdeveloped and used in this case study. Rather than using 'closeology' with the assumption that the reservoir quality is the same in a confined areawe use a large number of wells across all geologies to 'normalize' the geological differences. For a large enough sample size statistical theory states that each different completion type to be compared is equally represented in permeability and net pay space (reservoir flow capacity). If this is true, then statistical variations in cumulative production from one group to another are more representative of completion and hydraulic fracture effectiveness. Therefore, the cumulative production metric may be used to compare directly different completion types, number of stages, fracture designs, fluid systems, etc.
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