Expanding Sustainable Shale Gas Supply through Hydraulic Fracturing Efficiency Improvements

摘要

Commercial quantities of gas produced from shale resources can only be realized through reservoir stimulation, such as hydraulic fracturing. Although hydraulic fracturing is a proven production enhancement technique, there is much room for improvement in the design and execution of each hydraulic fracture stage as evident in production logs. In most cases, in long horizontal wells there are few very productive fracture stages with the majority of other stages producing little or no gas. By improving the efficiency of each hydraulic fracture stage, more gas can be produced while minimizing the input of energy and water, thus improving shale gas economics and reducing environmental impact. This paper examines the use of microseismic imaging and production logging on improving the design and efficiency of individual hydraulic fracture stages in the Marcellus shale. Microseismic data from a multi horizontal well pad, that included 93 fracture stages, was used to identify areas of natural fracture swarms, while production logs confirmed greater production in these zones. Furthermore, we present how microseismic imaging can be used to predict hydraulic fracturing interaction with natural fractures and how this interaction impacts hydraulic fracture design and spacing. By using the microseismic-cloud length-to-width aspect ratio, we were able to verify presence of natural fractures and propose a new, non uniform hydraulic fracture spacing design. Finally, we compare the production results with mud log gas shows and propose a method for determining hydraulic fracture spacing such that the great majority of stages - if not all - contribute significantly to the aggregate production.