Fractured shale-gas systems

Curtis, John B.

doi:10.1306/61eeddbe-173e-11d7-8645000102c1865d

Cited by 600 publications

(249 citation statements)

References 18 publications

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“…In the last few decades, the most of organic-rich shale-related plays, for example Barnett, Niobrara, Eagle Ford, Haynesville, and Bakken, have been labeled as "shale plays," and the terms "shale oil," "tight oil," and "resource play" are often used interchangeably in a public discourse [28][29][30][31][32]. The Barnett shale is a typical organic-rich siliceous shale (Figure 2a).…”

Section: Lithofacies Of Shalesmentioning

confidence: 99%

Sequence Stratigraphy of Fine-Grained “Shale” Deposits: Case Studies of Representative Shales in the USA and China

Jiang¹,

Zou²,

Dong³

et al. 2017

Seismic and Sequence Stratigraphy and Integrated Stratigraphy - New Insights and Contributions

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The fine-grained "shale" deposits host a vast amount of unconventional oil and gas resources. This chapter examines the variations in lithofacies, patterns of well logs, geochemistry, and mineralogy in order to construct a sequence stratigraphic framework of the representative marine Barnett, Woodford, Marcellus, Mowry, and Niobrara finegrained "shales" (USA) and the marine Longmaxi shale and lacustrine Chang7 lacustrine shale (China). Practical methods are proposed in order to recognize the sequence boundaries, the flooding surfaces, the parasequences and parasequence sets, the system tracts, and variation patterns of facies and rock properties. The case studies for the sequence stratigraphy in the USA and China have revealed that the transgressive systems tract (TST) and the early highstand systems tract (EHST, if identifiable) of finegrained "shales" have been deposited in anoxic settings. TST and EHST of the siliciclastic "shales" are characterized by high gamma ray, high TOC, and high quartz content, while TST and EHST of the carbonate-dominated fine-grained "shales" are characterized by low gamma ray, organic lean, and carbonate rich fine-grained deposits. The lithofacies, geochemistry, mineralogy, depositional evolution, and reservoir development have been predicted and correlated within a sequence stratigraphic framework for the suggested cases. The best reservoir with the best completion quality is developed in TST and HST in both siliciclastic-dominated and carbonate-dominated finegrained "shales."

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Section: Lithofacies Of Shalesmentioning

confidence: 99%

Sequence Stratigraphy of Fine-Grained “Shale” Deposits: Case Studies of Representative Shales in the USA and China

Jiang¹,

Zou²,

Dong³

et al. 2017

Seismic and Sequence Stratigraphy and Integrated Stratigraphy - New Insights and Contributions

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“…The Barnett shale lies at depths of 1 891 to 2 591 m with recoverable resources of 12 461×10 8 m 3 (Montgomery et al, 2005;Curtis, 2002), extends about 13 000 km 2 covering a gentle anticline and slope (Ground Water Protection Council, 2009), and has a resource abundance of 0.96×10 8 m 3 km -2 . Moreover, the Barnett shale has its own features in six aspects as: In terms of source rocks characteristics, the thickness of the shale varies from 30 to 183 m through a basin-scale with a mean TOC value of 4.5% (Curtis, 2002), and the type of kerogen for the Barnett shale as compared with that for the Longmaxi Formation is mainly oil-prone Type II kerogen indicating its thermal immaturity . Besides, the shale has experienced lower thermal maturity as 1.0% to 1.3% (Curtis, 2002).…”

Section: Marine Shale In the Fort Worth Basin United Statesmentioning

confidence: 99%

“…Moreover, the Barnett shale has its own features in six aspects as: In terms of source rocks characteristics, the thickness of the shale varies from 30 to 183 m through a basin-scale with a mean TOC value of 4.5% (Curtis, 2002), and the type of kerogen for the Barnett shale as compared with that for the Longmaxi Formation is mainly oil-prone Type II kerogen indicating its thermal immaturity . Besides, the shale has experienced lower thermal maturity as 1.0% to 1.3% (Curtis, 2002). The lithofacies of the shale is dominated by fine-grained (clay-to silt-size) particles including nonlaminated to laminated siliceous mudstone, laminated argillaceous lime mudstone (marl), and skeletal, argillaceous lime packstone (Loucks and Ruppel, 2007).…”

Section: Marine Shale In the Fort Worth Basin United Statesmentioning

confidence: 99%

“…For the petrophysical properties, the shale has a total porosity value as low as about 4% to a greatest of 5%, and the average permeability is generally less than 0.001 mD (Curtis, 2002). Compared to the Longmaxi Formation, the gas content for the Barnett shale ranges from 8.5 to 9.9 m 3 t -1 (Zou et al, 2014), and at reservoir PVT (pressure, volume, temperature) conditions (at 6% porosity, 70 ºC, and 26.2 MPa), a maximum storage of 4.96 m 3 t -1 is possible .…”

Section: Marine Shale In the Fort Worth Basin United Statesmentioning

confidence: 99%

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Methods for shale gas play assessment: A comparison between Silurian Longmaxi shale and Mississippian Barnett shale

et al. 2015

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Based on field work, organic geochemical analyses and experimental testing, a six-property assessment method for shale gas is proposed. These six properties include organic matter properies, lithofacies, petrophysical properties, gas content, brittleness and local stress field. Due to the features of continuous distribution over a large area and low resource abundance in shale plays, a sweet spot should have these following properties: (a) TOC>2%; (b) brittle minerals content (>40%) and clay minerals (<30%); (c) Ro (>1.1%); (d) porosity (>2%) and permeability (>0.000 1 mD), and (e) effective thickness (30-50 m). Applying these criteria in the Sichuan Basin, the Silurian Longmaxi shale consists of four prospecting sweet spots, including blocks of Changning, Weiyuan, Zhaotong and Fushun-Yongchuan. Although these four blocks have some similarities, different features were usually observed. After comprehensive analyses using the six-property assessment method, the Fushun-Yongan Block ranks the most favorable sweet spot, followed by the Weiyuan Block. For the other two blocks, the Changning Block is better than the Zhaotong Block. By comparing with the Mississippian Barnett shale, characteristics that are crucial for a high-yielding in the Sichuan Basin include a high content of organic matter (TOC>2.5%), a moderate thermal maturity (Ro=0.4%-2%), a high content of brittle minerals (quartz: 30%-45%), a high gas content (>2.5 m 3 t -1 ), and types I and II 1 kerogen. KEY WORDS: shale gas play, Silurian Longmaxi shale, Barnett shale, sweet spot, six-property assessment.

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“…The adsorption of gas in organic geomaterials can be described using an isotherm, among which Langmuir's is most widely used (Gensterblum et al 2015). For example, the gas content of five reservoirs in the USA, with in situ pressures between 2 and 28 MPa (600-8500 m deep), ranged from 1 to 10 m 3 / 1 3 ton, of which 20-85% was adsorbed in the organic content (Curtis 2002;Hill and Nelson 2000). Due to the multi-scale and multiple physical phenomena associated with shale gas production, the mechanism of gas flow is a combination of viscous (Darcy and non-Darcy) flow (Huang et al 2016), and gas-slippage (Klinkenberg) effect (Mehmani et al 2013), as well as continuum (Fickian), free-molecule (Knudsen), and surface (Yuan et al 2014) diffusions.…”

Section: Introductionmentioning

confidence: 99%

Elastic–Brittle–Plastic Behaviour of Shale Reservoirs and Its Implications on Fracture Permeability Variation: An Analytical Approach

et al. 2018

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Shale gas has recently gained significant attention as one of the most important unconventional gas resources. Shales are fine-grained rocks formed from the compaction of silt-and clay-sized particles and are characterised by their fissured texture and very low permeability. Gas exists in an adsorbed state on the surface of the organic content of the rock and is freely available within the primary and secondary porosity. Geomechanical studies have indicated that, depending on the clay content of the rock, shales can exhibit a brittle failure mechanism. Brittle failure leads to the reduced strength of the plastic zone around a wellbore, which can potentially result in wellbore instability problems. Desorption of gas during production can cause shrinkage of the organic content of the rock. This becomes more important when considering the use of shales for CO 2 sequestration purposes, where CO 2 adsorption-induced swelling can play an important role. These phenomena lead to changes in the stress state within the rock mass, which then influence the permeability of the reservoir. Thus, rigorous simulation of material failure within coupled hydro-mechanical analyses is needed to achieve a more systematic and accurate representation of the wellbore. Despite numerous modelling efforts related to permeability, an adequate representation of the geomechanical behaviour of shale and its impact on permeability and gas production has not been achieved. In order to achieve this aim, novel coupled poro-elastoplastic analytical solutions are developed in this paper which take into account the sorption-induced swelling and the brittle failure mechanism. These models employ linear elasticity and a Mohr-Coulomb failure criterion in a plane-strain condition with boundary conditions corresponding to both open-hole and cased-hole completions. The post-failure brittle behaviour of the rock is defined using residual strength parameters and a non-associated flow rule. Swelling and shrinkage are considered to be elastic and are defined using a Langmuir-like curve, which is directly related to the reservoir pressure. The models are used to evaluate the stress distribution and the induced change in permeability within a reservoir. Results show that development of a plastic zone near the wellbore can significantly impact fracture permeability and gas production. The capabilities and limitations of the models are discussed and potential future developments related to modelling of permeability in brittle shales under elastoplastic deformations are identified.

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Fractured shale-gas systems

Cited by 600 publications

References 18 publications

Sequence Stratigraphy of Fine-Grained “Shale” Deposits: Case Studies of Representative Shales in the USA and China

Sequence Stratigraphy of Fine-Grained “Shale” Deposits: Case Studies of Representative Shales in the USA and China

Methods for shale gas play assessment: A comparison between Silurian Longmaxi shale and Mississippian Barnett shale

Elastic–Brittle–Plastic Behaviour of Shale Reservoirs and Its Implications on Fracture Permeability Variation: An Analytical Approach

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