Impacto En Shale Gas

 

SPE 140555

Design of Multiple Transverse Fracture Horizontal Wells in Shale Gas Reservoirs
Bo Song, Texas A&M University; Michael J. Economides, University of Houston; and Christine Ehlig-Economides, Texas A&M University
Copyright 2011, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Hydraulic Fracturing Technology Conference and Exhibition held in TheWoodlands, Texas, USA, 24–26 January 2011. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Societyof Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.Abstract The game changing technology enabling economic natural gas production from shale is the multiple fracture well (MFTW), a horizontal well with multiple transverse fractures. The well itself can create a stimulated reservoir volume (SRV) that delineates sufficient gas reserves to payout the well and provide continued return for several decades. This paper shows the importance ofpermeability and adsorbed gas in ensuring a well design that will achieve these objectives. In this paper we base decisions about the number and size of fractures and the horizontal well length (and therefore the fracture spacing) first on the physics of production and then on investment economics. Current practices using a repetitive well template applied to all wells in a given shale gas play result insome wells doing far better than expected while others barely pay out. We show that linear flow is likely to dominate production behavior until pressure interference occurs between adjacent fractures and that the time of inter-fracture interference predicted by linear flow pressure penetration is prolonged by desorption. The shale permeability and the adsorbed gas parameters are used to design aneconomically successful well while ensuring at least 50% gas recovery in the SRV within a specified period of time. Field data from several shale gas formations are used to provide examples of the well design approach. The gas adsorption characterization typically comes from laboratory analysis, which we use to develop what we have called the adsorption index. Because the gas recovery factordepends on lowering the average pressure in the SRV, permeability and the adsorption index are used to estimate the time of inter-fracture interference, which in turn indicates the optimal spacing between fractures. This paper provides insights on the effective exploitation of a shale gas reservoir by optimizing the fracture and well architecture. Introduction Shale gas resource is playing asignificant role in today’s energy supply in the United States and Canada and is likely to evolve in other countries. By 2008, the natural gas resource potential for gas shale was estimated to be 50-100 Tcf (Cipolla et al 2009). There have been many other, speculative, reports that put shale gas potential several times these estimates. Success with the multiple transverse fracture well (MTFW) design isdemonstrating profitable gas production from this vast resource (Arthur, Bohm and Layne, 2008). Compared to conventional gas reservoirs, the permeability of shale gas formations is much lower, typically between 10 to 100 nano-Darcy (10-4 to 10-5 md) (Cipolla et al 2009). Moreover, unlike in conventional and even tight sandstone gas reservoirs where all the gas is stored as free gas, a large fraction...