Defining Regions of Hydraulic-Fracture Connectivity Aids in Designing Completions
- Adam Wilson (JPT Special Publications Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- March 2014
- Document Type
- Journal Paper
- 102 - 106
- 2014. Society of Petroleum Engineers
- 1 in the last 30 days
- 195 since 2007
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This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 166505, "Defining Three Regions of Hydraulic-Fracture Connectivity in Unconventional Reservoirs Helps in Designing Completions With Improved Long-Term Productivity," by Roberto Suarez-Rivera, SPE, Schlumberger; Larry Behrmann, Schlumberger consultant; Sid Green, SPE, Schlumberger and University of Utah; and Jeff Burghardt, SPE, Sergey Stanchits, Eric Edelman, SPE, and Aniket Surdi, Schlumberger, prepared for the 2013 SPE Annual Technical Conference and Exhibition, New Orleans, 30 September-2 October. The paper has not been peer reviewed.
Using large-scale hydraulic-fracturing experiments on tight shale outcrops, three dominant regions controlling stage production were identified—the connector between the wellbore and the fracture system, the near-wellbore fracture, and the far-wellbore fracture network. The particular nature of these regions may change depending on the play, the reservoir makeup, its relation to the in-situ stress, and the distribution of rock properties; however, these regions are always well differentiated. Understanding the role of each of these components in hydrocarbon production is fundamental to identifying the dominant sources of fracture-conductivity loss and accelerated production decline.
Achieving economic production from nanodarcy-scale-permeability, organic-rich- mudstone reservoirs requires creating large surface area by hydraulic fracturing. More importantly, economic production depends on preserving the created surface area and fracture conductivity during long-term production. This paper is about understanding the surface area (fracture geometry) that is created in heterogeneous rocks with complex makeup, preserving the surface area after fracturing, and maintaining adequate fracture conductivity during long-term production.
Fig. 1 shows a conceptual representation of the interaction of the propagating fracture with weak interfaces and weak bedding as a function of distance from the wellbore. Branching and stepovers (not shown) also develop vertically, providing resistance to flow and to upward fracture growth. Three regions of fracturing with unique properties emerge from this concept: the wellbore/fracture connector, the near-wellbore fracture, and the far-wellbore fracture. The wellbore connector (possibly 10–30 ft) is the region of highest hydraulic convergence and appears to be a choking point for production. This is particularly so if it is not propped appropriately. The near-wellbore fracture is of limited extent (200–400 ft) and represents most of the propped surface area and possibly most of the produced hydrocarbons. Unfortunately, proppant transport in the far-wellbore fracture region is minimal; the created far-field surface area is easily lost and does not contribute to production. This loss of surface area at the farwellbore region may not be avoidable by operational changes at the wellbore.
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