The Key Factors That Determine the Economically Viable, Horizontal Hydrofractured Gas Wells in Mudrocks
KAUST DepartmentAli I. Al-Naimi Petroleum Engineering Research Center (ANPERC)
Earth Science and Engineering Program
Energy Resources & Petroleum Engineering
Energy Resources and Petroleum Engineering
Energy Resources and Petroleum Engineering Program
Physical Science and Engineering (PSE) Division
Permanent link to this recordhttp://hdl.handle.net/10754/662819
MetadataShow full item record
AbstractWe assemble a multiscale physical model of gas production in a mudrock (shale). We then tested our model on 45 horizontal gas wells in the Barnett with 12–15 years on production. When properly used, our model may enable shale companies to gain operational insights into how to complete a particular well in a particular shale. Macrofractures, microfractures, and nanopores form a multiscale system that controls gas flow in mudrocks. Near a horizontal well, hydraulic fracturing creates fractures at many scales and increases permeability of the source rock. We model the physical properties of the fracture network embedded in the Stimulated Reservoir Volume (SRV) with a fractal of dimension D < 2 . This fracture network interacts with the poorly connected nanopores in the organic matrix that are the source of almost all produced gas. In the practically impermeable mudrock, the known volumes of fracturing water and proppant must create an equal volume of fractures at all scales. Therefore, the surface area and the number of macrofractures created after hydrofracturing are constrained by the volume of injected water and proppant. The coupling between the fracture network and the organic matrix controls gas production from a horizontal well. The fracture permeability, k f , and the microscale source term, s, affect this coupling, thus controlling the reservoir pressure decline and mass transfer from the nanopore network to the fractures. Particular values of k f and s are determined by numerically fitting well production data with an optimization algorithm. The relationship between k f and s is somewhat hyperbolic and defines the type of fracture system created after hydrofracturing. The extremes of this relationship create two end-members of the fracture systems. A small value of the ratio k f / s causes faster production decline because of the high microscale source term, s. The effective fracture permeability is lower, but gas flow through the matrix to fractures is efficient, thus nullifying the negative effect of the smaller k f . For the high values of k f / s , production decline is slower. In summary, the fracture network permeability at the macroscale and the microscale source term control production rate of shale wells. The best quality wells have good, but not too good, macroscale connectivity.
CitationHaider, S., Saputra, W., & Patzek, T. (2020). The Key Factors That Determine the Economically Viable, Horizontal Hydrofractured Gas Wells in Mudrocks. Energies, 13(9), 2348. doi:10.3390/en13092348
SponsorsThe authors thank the Ali I. Al-Naimi Petroleum Engineering Research Center (ANPERC) at KAUST for supporting this research. We thank Michael Marder of UT Austin for a careful review of this paper and helpful suggestions for further improvement. We thank both reviewers for their excellent remarks that were all incorporated into the paper. Special thanks go to Reviewer 1, for giving us the intellectual pleasure of responding to his penetrating questions.
Except where otherwise noted, this item's license is described as This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license .