Impact of Proppant Distribution in Hydraulic Fracture on the Productivity of the Multi-Stage Fractured Marcellus Shale Horizontal Wells

Abstract

ABSTRACT The impact of the proppant distribution within the hydraulic fracture on the productivity of the multi-stage fractured Marcellus shale horizontal well has been investigated. The available data from a Marcellus Shale horizontal well were compiled, analyzed using a fracture model to determine the fracture properties, and used to develop a reservoir model. Multipliers for permeability and conductivity were incorporated in the model to account for the dynamic net stress changes during the production. The model predictions were found to be in close agreement with the well production. The impact of the non-uniform fracture conductivity and stage spacing on gas production were then investigated. The non-uniform fracture conductivity has a significant impact on the initial gas production. Therefore, it is important to consider the impact of the non-uniform fracture conductivity in optimizing hydraulic fracturing treatments in Marcellus shale. INTRODUCTION The application of the horizontal drilling and hydraulic fracturing techniques have unlocked, significant natural gas reserves from shale gas reservoirs. Marcellus Shale is one of the most prolific and largest unconventional gas resources in US. There are approximately 95,000 square miles of Marcellus shale in Ohio, West Virginia, and Pennsylvania as well as areas in New York, Kentucky, Tennessee, and Maryland. Marcellus shale varies in thickness from 50 to 200 ft. The depth of the shale ranges from 4,000 to 8,500 ft. The average temperature of the Marcellus shale is 150°F. The total organic carbon (TOC) ranges from 2 to 20 percent in Marcellus Shale (Boyce et al., 2010). Hydraulic fracture treatment involves injecting fluid into the wellbore in order to increase the downhole pressure to a level in excess of the fracturing pressure of the formation. In response to this increase in pressure, the formation cracks, allowing the injected fluid to enter and extend the crack further into the formation. To keep the crack open after injection, a solid proppant, such as sand, is mixed with the injected fluid. Proppant plays an important role in stopping fractures from closing under in-situ formation stress and maintaining the fracture conductivity. There is a greater degree of closure in the unpropped areas, and their conductivity is poorer than in the propped areas. The distribution of proppant within the fracture can significantly affect the productivity of the well. The Marcellus Shale is typically treated with 2,500 to 20,000 barrels of water and 25,000 to 75,000 pounds of sand proppant at a rate of 25 to 100 barrels per minute (Bruner and Smosna, 2011).