Geological Life Cycle Inventory Model Development for Shale Gas Resources

Abstract

This paper presents an innovative life cycle assessment approach for shale gas production, which integrates geological system characteristics with a surface emission model to estimate the overall GHG emissions. Firstly, the model developed incorporates a Volumetric Estimation technique, Flowing Material Balance and Advance Decline Curve analysis to estimate the field gas in-place and estimated ultimate resource (EUR). Next, this geological model is integrated with the surface emission model, which is based on engineering design and operational parameters, to estimate the GHG as well as other emissions (direct and indirect; gaseous, liquid, solid waste) and resource use (materials, energy, water) from site construction, drilling, hydraulic fracturing, well completion, well head operations, gas gathering and gas processing. The cradle to gate LCA model developed was applied to the Fayetteville shale gas field using public domain data. Three possible field development strategies were developed and implemented in the life cycle inventory model developed. They all comply with the outputs of the subsurface constraint inventory model but differ in terms of selected parameters in well construction, well drilling, hydraulic fracturing, well completion, well head and surface facilities operations. The annual GHG emissions of Fayetteville shale gas field production with a sensitivity analysis was estimated for the three different field development strategies. The resulting life cycle GHG emissions range between 12.79 and 21.09 CO2 equivalents per Mscf of gas produced or 13.65 to 22.51 CO2 equivalents per MJ of gas produced. The water consumption is estimated in the range of 18 litres of water per Mscf of gas production.