Abstract
The influence of complex natural fractures on multiple shale-gas well performance with varying well spacing is poorly understood. It is difficult to apply the traditional local grid refinement with structured or unstructured gridding techniques to accurately and efficiently handle complex natural fractures. In this study, we introduced a powerful non-intrusive embedded discrete fracture model (EDFM) technology to overcome the limitations of exiting methods. Through this unique technology, complex fracture configurations can be easily and explicitly embedded into structured matrix blocks. We set up a field-scale two-phase reservoir model to history match field production data and predict long-term recovery from Marcellus. The effective fracture properties were determined thorough history matching. In addition, we extended the single-well model to include two horizontal wells with and without including natural fractures. The effects of different numbers of natural fractures on two-well performance with varying well spacing of 200 m, 300 m, and 400 m were examined. The simulation results illustrate that gas productivity almost linearly increases with the number of two-set natural fractures. Furthermore, the difference of well performance between different well spacing increases with an increase in natural fracture density. A larger well spacing is preferred for economically developing the shale-gas reservoirs with a larger natural fracture density. The findings of this study provide key insights into understanding the effect of natural fractures on well performance and well spacing optimization.
Highlights
Typical shale gas reservoirs consist of free gas and adsorbed gas
We developed an innovative non-intrusive embedded discrete fracture model (EDFM) technology in conjunction with any third-party reservoir simulators with structured grids to accurately and efficiently handle any complex hydraulic and natural fractures [30,31], which provides a unique solution to overcome the above limitations of existing methods
We introduced the non-intrusive EDFM technology in conjunction with a commercial reservoir simulator of CMG-GEM [32] to simulate shale gas production considering complex natural fractures and two-phase flow
Summary
Typical shale gas reservoirs consist of free gas and adsorbed gas. Economic shale gas production has been enabled by the advanced technologies of multiple horizontal wells and multi-stage hydraulic fracturing. The U.S Energy Information Administration (EIA) estimates that dry shale gas production (0.48 trillion cubic meters) accounts for around 62% of the total U.S dry natural gas production in. The Marcellus shale formation is the most productive gas field in the United States. It has been reported that natural fractures are commonly observed in many shale gas formations based on outcrops, cores and image logs [2]. Engelder et al [3] observed that there are two sets of natural fractures or two regional joint sets (J1 and J2 sets) in the Marcellus shale formation, which significantly
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