Summary

The advances in horizontal drilling and hydraulic fracturing technologies have enabled shale gas production economically. Although there are a huge number of horizontal wells drilled in many shale gas reservoirs, well performance and completion effectiveness are still poorly understood. The different features of shale gas reservoirs from conventional gas reservoirs, such as non-Darcy flow behavior, gas adsorption/desorption, geomechanics (stress-dependent fracture conductivity) are not investigated completely. In addition, there are high uncertainties in shale and fracture properties such as fracture half-length and conductivity. Also, the cost of fracture treatments is high. Hence, it is absolutely important to systematically evaluate these unique features of shale gas reservoirs, quantify the rank of key parameters, and optimize fracture treatment design through economic analysis.

In this work, based on the typical reservoir and fracture properties of Marcellus Shale, we evaluated the effects of non-Darcy flow behavior, gas desorption, and geomechanics on well performance. Additionally, we compared bi-wing fracture and fracture network models. Subsequently, we used the Design of Experiment (DoE) method to perform sensitivity study to quantify the rank of important parameters in short-term and long-term production periods. Six uncertainty parameters including fracture height, fracture conductivity, fracture half-length, cluster spacing, permeability and porosity were investigated. According to the rank of significant parameters, we performed history matching with one field production well. Based on the history matching results, the range of key fracture parameters such as fracture half-length, height, and conductivity was determined. Additionally, a 30-year production forecasting was performed and its corresponding EUR was quantified. Finally, optimization of fracture design was conducted in combination with economic analysis. This work can provide significant insights into quantifying the uncertainty, characterization of fracture properties, and optimization of fracture design for the current development of the Marcellus Shale.

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