Horizon Attributes and Fracture-Swarm Sweet Spots in Low-Permeability Gas Reservoirs

Horizon Attributes and Fracture-Swarm Sweet Spots in Low-Permeability Gas Reservoirs B.S. Hart; B.S. Hart McGill University Search for other works by this author on: This Site Google Scholar R.A. Pearson; R.A. Pearson McGill University Search for other works by this author on: This Site Google Scholar J.M. Herrin; J.M. Herrin New Mexico Institute of Mining and Technology Search for other works by this author on: This Site Google Scholar T. Engler; T. Engler New Mexico Institute of Mining and Technology Search for other works by this author on: This Site Google Scholar R.L. Robinson R.L. Robinson New Mexico Institute of Mining and Technology Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 2000. Paper Number: SPE-63207-MS https://doi.org/10.2118/63207-MS Published: October 01 2000 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Hart, B.S., Pearson, R.A., Herrin, J.M., Engler, T., and R.L. Robinson. "Horizon Attributes and Fracture-Swarm Sweet Spots in Low-Permeability Gas Reservoirs." Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 2000. doi: https://doi.org/10.2118/63207-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractHorizon attributes, i.e., attributes that numerically describe geometric characteristics of interpreted horizons from conventional (i.e., p-wave) 3-D seismic volumes, hold considerable potential for identifying fracture-swarm sweet spots in low permeability reservoirs. Typically, these attributes (e.g., dip, azimuth, and curvature) are used to define subtle faults that are near the limit of seismic detectability. These subtle structures can play important roles in compartmentalizing conventional reservoirs. However, in low permeability gas reservoirs where fracture permeability is critical, these same attributes can be used to define high-permeability fracture swarms. We illustrate this point with three case studies, two clastic the other carbonate, from the San Juan Basin area of northwestern New Mexico. The Paradox Formation is a Pennsylvanian age low permeability carbonate reservoir. At Ute Dome Field, production characteristics indicate that fractures are the main control on gas production from these carbonates. Comparison of horizon attributes from this level with production data shows that these attributes are defining high-permeability fracture swarms associated with faults. The Mesaverde Group consists of Cretaceous age clastics and is a tight reservoir in the Blanco Field. Again, horizon attributes (including curvature attributes) can be used to define fault-related fracture swarms that will produce at higher rates than surrounding areas. The Dakota Sandstone is another Cretaceous tight gas sandstone. A map of horizon dip in one area shows a trend that is associated with anomalous production from two wells. However, these two wells cannot be described as "sweet spot" wells because their production is not anomalously high. These observations indicate that development drilling plans for low permeability reservoirs should take into account geologic heterogeneity that can be associated with fracture swarms. Undrilled fracture swarms should be targeted to produce high-rate wells. On the other hand, offset wells should specifically avoid drilling into previously tapped fracture swarms to avoid drainage interference. Other factors that need to be considered are:the orientation of the fractures with respect to in-situ stress directions, andlithologic (i.e., stratigraphic) control on fracture density.IntroductionLow-permeability gas reservoirs are an important resource in the United States, with some estimates suggesting that approximately one half of future natural gas supplies will be produced from these technologically challenging reservoirs1. In both clastic and carbonate reservoirs with low matrix permeability, natural fractures are commonly considered to play an important role in enhancing bulk permeability, thus enabling wells to produce at commercial rates. The importance of these challenging reservoirs is likely to grow with time, and we suggest that multidisciplinary integration is critical during all phases of reservoir exploration and development.In this paper we demonstrate the utility of conventional 3-D seismic data for identifying "fracture-swarm sweet spots" in low permeability reservoirs. These sweet spots are defined by wells that produce at rates that are much greater than neighboring wells. Typically, they also produce more gas than neighboring wells. In the examples we describe below, the enhanced production is thought to be the result of fracture swarms that are associated with permeability enhancing faults or flexures of relatively brittle carbonates or clean sandstones. We distinguish these fracture swarms from more homogeneously distributed "regional fractures" that, ideally, share a common orientation and spacing over relatively broad areas. Harstad et al.2 demonstrated the importance of characterizing regional fracture networks when planning infill drilling in tight-gas sandstones. Keywords: seismic data, anomaly, orientation, upstream oil & gas, reservoir, fracture-swarm sweet spot, natural fracture, mesaverde, sandstone, sweet spot Subjects: Reservoir Characterization, Seismic processing and interpretation This content is only available via PDF. 2000. Society of Petroleum Engineers You can access this article if you purchase or spend a download.

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