A New Hydraulic Fracture Tip Mechanism in a Statistically Homogeneous Medium

Chudnovsky, A.; Fan, Jian Chun; Shulkin, Y.; Dudley, J. W.; Shlyapobersky, J.; Schraufnagel, R.A.

doi:10.2118/36442-ms

Cited by 15 publications

(10 citation statements)

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“…Such an invasion phenomenon ahead of the fracture tip is significantly different from that observed in competent rocks, where the fluid front is normally behind the tip. 8,9 Fig. 7a shows the tip of a fracture in Test #1; the fracture plane is perpendicular to the page.…”

Section: Test Results and Discussionmentioning

confidence: 99%

“…Much work has been carried out to identify and model the near-tip processes that influence the net injection pressure and the propagation of fractures in competent rocks. 8,9 However, the mechanisms applicable to these formations are significantly different from those of non-cohesive, soft sands. For example, as is explained later in this paper, tip propagation in unconsolidated formations is accompanied by large leakoff, inelastic deformation and shear failure, as well as formation damage.…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic Fracturing Stimulation in Poorly Consolidated Sand: Mechanisms and Consequences

Khodaverdian

McElfresh

2000

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA series of hydraulic fracturing injection experiments was performed in unconsolidated sand in a radial flow cell (RFC) to delineate the fundamental mechanisms controlling fracture propagation. The results of this work will be used to optimize the current fracpacking practices in unconsolidated and poorly consolidated sand and to develop adequate modeling techniques. Although the generic word "fracture" is used throughout this document and elsewhere to describe injectioninduced formation parting during stimulation, it will be made clear that the tip propagation mechanisms in unconsolidated sand are fundamentally different from linear elastic fracture mechanics (LEFM) as defined for competent rocks.Conceptually, the RFC used for the injection tests simulates a 1-ft thick section of unconsolidated sand formation within a 3-ft radius of a wellbore. The tests in this system included injection of cross-linked guar and visco-elastic surfactant into 3,000 md sand samples subjected to different overburden stresses. The following is a summary of the findings: • The experimental data suggest that "fracture" propagation in unconsolidated sand is primarily a result of shear failure in a process-zone ahead of the fracture tip. The shear failure is caused by large tip stresses (due to tip plasticity) and by pore pressure increase within the process zone.• Uncharacteristically large net fracturing pressures (NFP) were encountered for low-efficiency fluids. Generally, the NFP increased with decreasing fluid efficiency.• Multiple sub-parallel fracturing and complex fracture geometry was encountered. Sub-parallel fractures may be initiated at the tip or at the fracture wall due to shear failure and is dependent on the fluid efficiency and the type of leakoff, i.e., wall building or viscous. The field consequences of sub-parallel fracturing during stimulation may include premature screenout and fracture bridging, short fracture length and extensive formation damage as the fracturing fluid invades the sheared interfaces.

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Section: Test Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydraulic Fracturing Stimulation in Poorly Consolidated Sand: Mechanisms and Consequences

Khodaverdian

McElfresh

2000

Proceedings of SPE Annual Technical Conference and Exhibition

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“…The most sophisticated models predict the size of the fluid lag region and the pressure distribution in the fracture [21]. The most sophisticated models predict the size of the fluid lag region and the pressure distribution in the fracture [21].…”

Section: (2)mentioning

confidence: 99%

“…The most sophisticated models predict the size of the fluid lag region and the pressure distribution in the fracture [21]. These models when compared with field data often simulate too high net pressures for early injection times and too low net pressures for poorly contained fractures at late times [21]. This assumption was valid for viscous fluid [22].…”

Section: (2)mentioning

confidence: 99%

“…These models formulate a uniform pressure drop in the main body of the fracture and a rapid pressure drop near the fracture tip. Tip dilatancy-Inelastic rock behavior near the tip of the fracture has been proposed to be one of the possible mechanisms to explain why fluid lag behavior fails to simulate the observed net pressures in the field [21]. Also they state that the fracture geometry can vary significantly after shut in.…”

Section: (2)mentioning

confidence: 99%

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Fracture Height Containment in the Stimulation of Oriskany Formation

Vatsa

Wang

2013

Journal of Energy Resources Technology

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The Oriskany sandstone formation has been a prolific producer of natural gas in the Appalachian basin since 1930s. Lot of production wells have been converted to gas storage wells for the ease of operation. Natural gas storage industry is a vital part of North American energy driven economy because of the fluctuation in seasonal demand and in maintaining the reliability of supply needed to meet the demands of the consumer. However, the storage wells suffer from an annual deliverability loss of 5% owing to the various damage mechanisms. A lot of work pertaining to the is.me of identification of damage mechanisms and subsequent development of stimulation technology in order to mitigate the damage and restore the wells deliverability have been done in a joint effort between The Gas Research Institute, Department of Energy, American Gas Association and the various other operator companies involved in the storage industry. Operators mostly rely on traditional methods such as blowing, washing, reperforating, acidizing, infill drilling to restore wells deliverability. These traditional methods do provide short term benefits, but the longevity is not sustained and the overall situation remains same. Hydraulic fracturing is not preferred in terms of legitimate concerns over excessive vertical height growth, long fracture fluid cleanup times, lack of expertise and cost. This research study was carried out to understand the various damage mechanisms affecting the Oriskany wells, with a focus on gas storage wells. We then developed a dataset of reservoir properties, rock properties and fracture treatment data for Oriskany based on a complete literature review and calculations from a sonic log. Parametrical studies were carried out to investigate the effect of type of fracture fluids, injection rate, types ofproppant, treatment volume, reservoir pressure and treatment schedule on fracture geometries in the Oriskany formation. Based on the results, we developed new stimulation methods that lead to increased well deliverability, fracture height containment, and higher average fracture conductivity. This new understanding and knowledge help in practicing engineers design better treatments in stimulating Oriskany wells.

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