Intrinsic anisotropy due to layering as well as induced anisotropy due to fractures play critical role in fluid flow in organic-rich shales. In this paper, we characterize the impact of natural and induced fractures on permeability anisotropy utilizing various resolution CT-scans and present the effect of stress on the permeability of such fractured reservoirs. The effect of shale layering on fluid flow is also discussed.Wettability is another key factor in determining the fluid flow and recovery efficiency in shale reservoirs. We investigated the wettability of several shale samples from Eagle Ford, Mancos, Green River, Bakken and Niobrara shale plays. The effects of total organic carbon and maturity on contact angle in these shale formations are presented.

Although petroleum industry has obtained a good practice in unlocking the shale reservoirs, more comprehensive geomechanical experimental and modeling research is required to optimize the drilling, completion and hydraulic fracturing processes due to the significant heterogeneity and anisotropy of shale formations. Acoustic and mechanical properties strongly depend on several factors including the mineralogy, density and distribution of natural fractures, bedding plane orientation, total organic carbon (TOC), maturity and in-situ stress state and pore pressure which are significantly different in various shale reservoirs and even within a shale basin. The strong anisotropy of acoustic and mechanical properties has a major impact on the reservoir characterization and field development plan. In this paper, we present the results of an experimental study on several U.S. shale basins with different maturity including Eagle Ford, Green River and Mancos shales to provide more insight on the shale acoustic and mechanical properties. We discuss the effect of shale bedding plane orientation and emphasize on the impact of shale mineralogy and petrophysical characteristics on the acoustic and mechanical properties. The mineralogy and petrophysical properties of each shale sample have been examined. Using both ultrasonic and mechanical methods, dynamic and static Young Modulus and Poisson's Ratio have been obtained at different bedding plane angles. A relationship between dynamic and static moduli has been consequently developed to determine in situ static moduli directly from seismic or well log data obtained in the same field. IntroductionAs the global energy demand increases with limited undiscovered conventional reserves left, the developments of unconventional reservoirs have been increasing worldwide. Shale formations have various minerals and vary in their petrophysical and geochemical properties from the conventional reservoirs. Therefore, they introduce new challenges to the oil and gas industry on many development stages. These challenges need further laboratory and field research, and require a more integrated, multi-disciplinary approach to study their characteristics.An accurate evaluation of the formation mechanical properties along with other factors leads to a successful implementation of drilling, completion and hydraulic fracturing in shale reservoirs. Types of mineralogy, clay URTeC 2013

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Published numerical and analytical solutions for wellbore stability predict certain trends in the behavior of hole geometry as a function of time. In general, shear failure is expected to increase in severity with time to produce over-gauged hole sections. However, these solutions do not take into account many aspects of the disturbances produced throughout the drilling process. An investigation of the behavior of hole geometry of a diverse group of wells is conducted to uncover the different relationships between the time-dependent wellbore stability and the related operational practices. The highlighted relationships are then reconciled with published wellbore stability solutions. The disturbances produced throughout the drilling process can include heat transfer between the drilling fluid and the wellbore wall, chemical interactions with the drilling fluid, and mechanical forces working on the wellbore wall. A diverse group of wells in terms of drilling fluid used, drilling practices employed, lithology of formations drilled, and time of exposure experienced is used to highlight the relationships between these disturbances and the time-dependent stability. To aid in illustrating these relationships, the mechanical properties and the stresses are estimated from open-hole wireline logging data. The relationship between time and wellbore stability was observed to reverse from the norm in some cases. It is believed that the anticipated charging of the local pore pressure due to the hydrostatic head overbalance and the heat transfer between the drilling fluid and the formation both combined with different operational practices and drilling events to produce this reversal in the relationship. The drilling events considered include long exposure times due to logging runs and troubles, well control events, lost circulation events, and reaming operations. The observed relationship is then compared with published time-dependent wellbore stability solutions where a form of reconciliation is produced. The presented change in the time-dependency relationships can open new doors for a more sophisticated computational modeling of wellbore stability.