Geomechanics Field and Laboratory Characterization of Woodford Shale: The Next Gas Play

Abousleiman, Younane N.; Tran, Minh; Hoang, Son K.; Bobko, Christopher P.; Ortega, Alberto; Ulm, Franz Josef

doi:10.2118/110120-ms

Cited by 88 publications

(43 citation statements)

References 20 publications

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“…Near wellbore stress condition can control the initiation and propagation of hydraulic fracture, and the size of hydraulic fracture and injected fluid can also change the stress field in the reservoir. Also the real time change along the near wellbore can change the hydraulic fracture direction and affect the production greatly [3,9,90]. The differences in far-field principal stress can alter the direction of hydraulic fractures and also determine whether there is a main fracture or there are many secondary fractures, as well as the shape of fracture has also been constrained [23,88].…”

Section: Influences Of In-situ Stresses On Hydraulic Fracturingmentioning

confidence: 99%

A review on hydraulic fracturing of unconventional reservoir

et al. 2015

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a b s t r a c tHydraulic fracturing is widely accepted and applied to improve the gas recovery in unconventional reservoirs. Unconventional reservoirs to be addressed here are with very low permeability, complicated geological settings and in-situ stress field etc. All of these make the hydraulic fracturing process a challenging task. In order to effectively and economically recover gas from such reservoirs, the initiation and propagation of hydraulic fracturing in the heterogeneous fractured/ porous media under such complicated conditions should be mastered. In this paper, some issues related to hydraulic fracturing have been reviewed, including the experimental study, field study and numerical simulation. Finally the existing problems that need to be solved on the subject of hydraulic fracturing have been proposed.Unconventional gas mainly includes shale gas, tight gas and coal seam gas. Shale gas is commonly in mudstone, shale and between them the interlayers of sandstone. Tight gas often has been stored in tight sandstone or sometimes limestone. Coal bed methane is contained within coal seams. Their common attribute is that the permeability of the matrix is very low, and the permeability often has been improved by artificial or natural fractures [55]. However, the differences between them are also significant. For example, the effective shale thickness for gas production should be more than 15 m while the height of coal is generally from 0.6 m to 5.0 m [68], as coal seams to be fractured may be multiple and thin, hydraulic fracturing in coal needs to be more accurately designed and controlled. Moreover, the Young's modulus of coal is smaller than shale and tight sandstone, the permeability of coal is more sensitive to stress due to the development of cleat system, and leakoff in coal may be more severe, which can significantly affect the fracturing result. Due to the complexity of unconventional reservoirs, it is challenging to predict the initiation and propagation of hydraulic fractures [39]. For example, the complex in situ stress state and distribution of rocks of varied attributes, which may change the profile of hydraulic fractures [38]; the existence of arbitrary pre-existing interfaces may diversify or arrest hydraulic fractures [93]; the temperature effect [75]; the fluid loss and transport of proppant; the competition between hydraulic fractures, and its recession and closure [4]. Thus, it is crucial to explore how hydraulic fracturing process will happen in complex geological settings.Firsthand materials of hydraulic fracturing come from in-door experiments, and field study. Laboratory study undergoes from small-scale rock samples with several cubic centimetres to large ones with one cubic metre or more. Since it is easy to control the stress conditions and make artificial structures within samples, hydraulic fracturing process with different stress field and rock structures can be conveniently studied. Especially in large scale experiments, it is possible to build a full size borehole, or to contr...

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Section: Influences Of In-situ Stresses On Hydraulic Fracturingmentioning

confidence: 99%

A review on hydraulic fracturing of unconventional reservoir

et al. 2015

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“…Significant organic content (kerogen) is also present throughout the formation. The geomechanics of the Woodford Shale has been extensively studied in previous publications (Abousleiman et al, 2007Sierra et al, 2010). Based on the published data, mechanical and petrophysical properties necessary for the simulation of the thick wall cylinder test on the Woodford Shale are presented in Table 3.…”

Section: Simulations Of Thick Wall Cylinder Tests On Woodford Shalementioning

confidence: 99%

Openhole Stability and Solids Production Simulation of Emerging Gas Shales Using Anisotropic Thick Wall Cylinders

Hoang

Abousleiman

2010

IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition

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Although unconventional gas shales have become accepted as the game changer for natural gas (International Energy Agency's 2009 World Energy Outlook), laboratory as well as simulated data of openhole completion and production accounting for the inherent anisotropy and low permeability of gas shales are still extremely limited, due to the great challenges in testing and modeling of shale under in-situ openhole conditions. First, shale frequently exhibits substantial mechanical anisotropy that affects the stress distribution around an open hole. Second, the intrinsic low permeability of shale, sometimes on the order of nano-Darcies, magnifies the effects of time-dependent pore pressure on the effective stresses and could cause complex rock failure behavior. In this study, the response of anisotropic thick wall cylinder shale samples under realistic laboratory time-dependent loading, simulating near-wellbore or near-perforation production stresses, is modeled and analyzed taking into account fully coupled fluid and shale matrix interaction to address these challenging issues. Extensive experimental results including thick wall cylinder tests on an anisotropic low-permeability shale were analyzed using the developed analytical simulator. The analysis showed that depending on shale permeability and loading rate, solids production could result from either shear collapse mechanism or a combination of shear and tensile failure of the rock matrix. Thick wall cylinder tests on Woodford Shale and Barnett Shale were also simulated using experimentally measured mechanical and petrophysical properties. The results showed that the stress required to initiate solids production significantly depends on the loading rate as well as sample size, and is considerably higher than predicted by conventional elasticity theory. The presented modeling will be essential for designing and interpreting thick wall cylinder tests on gas shales as well as the ensuing modeling of gas production from these formations. The results on Woodford Shale and Barnett Shale will serve as guidelines for field operations and future laboratory testing.

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“…This apparatus is is illustrated in Figure 1. Previous papers 17,18,19 have demonstrated the use of the IDSTD apparatus in the studies of fluid interaction with shales, and patent applications for the device have been filed 20 .…”

Section: Purpose Of This Workmentioning

confidence: 99%

“…The Woodford shale is more competent than the West Africa shale, as demonstrated in rock strength testing with mineral oil 21 . Properties of the Woodford shale have been presented in earlier papers [17][18][19] .…”

Section: Shales Testedmentioning

confidence: 99%

Changing Shale Strengths With Invert Emulsion Drilling Fluids: Theory, Measurement, and Modeling

Hemphill

Duran

2009

Latin American and Caribbean Petroleum Engineering Conference

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Problems with wellbore stability while drilling in shale have plagued the drilling industry for a long time. For good reason, the bulk of trouble-related problems while drilling have been in shales, and great expeditures in time and money are made each year dealing with the problem. However, shale interaction with drilling fluids in the drilling process remains a complex and often misunderstood area of study. By comparison, fewer wellbore stability problems occur while drilling with invert emulsion fluids (IEF) than when water-based drilling fluids are used. The theory of shale interaction with invert emulsions is briefly reviewed in this paper.Actual measurements of changes in shale strength of two shales have been recently made using a new test device from the University of Oklahoma. Two very different shales were studied: one from a deepwater environment and the other a more-competent shale cored in a land-drilling operation. These shales were exposed to invert emulsions having different water phase salinities, and the stresses required to cause sample failure were measured under in-situ conditions. The results showed use of invert emulsions under some conditions weakened the shales, while under other conditions, the shales were strengthened. These results were then interpreted using current osmotic pressure and membrane efficiency theory of invert emulsions.The results were compared to the elastic and porochemoelastic modeling using the rock mechanical properties determined in the laboratory testing. Using a set of drilling and wellbore in-situ stress conditions, traditional elastic wellbore stability modeling is used to predict the changes in tangential stress in the wellbore wall. Next, porochemoelastic modeling is used to predict changes in pore pressure as a function of time and of IEF water phase salinity (WPS). These results are then discussed in relation to the changes in shale strength seen in the laboratory.Knowing that there are significant differences in rock strengths of shales exposed to invert emulsions having varying water phase activity levels, the drilling engineer can more effectively plan future wells, especially those having narrow safe drilling windows.

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Geomechanics Field and Laboratory Characterization of Woodford Shale: The Next Gas Play

Cited by 88 publications

References 20 publications

A review on hydraulic fracturing of unconventional reservoir

A review on hydraulic fracturing of unconventional reservoir

Openhole Stability and Solids Production Simulation of Emerging Gas Shales Using Anisotropic Thick Wall Cylinders

Changing Shale Strengths With Invert Emulsion Drilling Fluids: Theory, Measurement, and Modeling

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