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The Relationship Between Net Pressure Development During Hydraulic Fracture Treatments and Productivity in Fruitland Coal Completions
This paper describes an innovative fracture treatment design approach that has been successfully used to improve the productivity of Fruitland coal CBM completions. The process integrates real-time treating pressure evaluation to adjust key treatment parameters on the fly and maintain a low net pressure development. The low net pressure development indicates good proppant distribution through the created fracture geometry and minimizes potential formation/fracture damage from the fracturing fluids. This results in shorter dewatering periods and accelerates peak production of the Fruitland Coal completions.
In the Fruitland Coal, the dominant fracturing mechanism controlling the ability to distribute proppant laterally into the far-field is the quality of the near-wellbore connection. Complex near-wellbore fracture geometries result in a convoluted slurry pathway, which hinders lateral proppant distribution into the far-field. Further, if the near-wellbore connection was not mitigated effectively, the overall net pressure development while placing proppant became excessive. This paper discusses the innovative changes made to improve the near-wellbore connection, allowing the treatment to be completed and productivity of the well increased.
Based on an offset well study, it was observed that excess net pressure development damaged the fracture conductivity and/or the cleat system of the coal. When an excessive level of net pressure was developed, polymer dehydration into the cleat system caused irreparable damage to the existing permeability. Evidence of the damage was indicated by the extended load fluid recovery time. Since de-watering of the coal begins only after the load is recovered, it was observed that gas production was significantly delayed when the net pressure development during the propped fracture treatment was excessively high.
Observing this relationship, treatment designs were altered, but more importantly, real-time assessment of the treatment pressure character was found to be essential in achieving design objectives. The completion approach discussed in this paper has been employed in over thirty-five Fruitland Coals completions over the past three years with excellent production results.