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Summary 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. Introduction Permeability is a key petrophysical property that influences the production rate from any gas or oil reservoir. Obtaining the permeability of organic-rich shales is challenging due to the intrinsic ultra-low matrix permeability, layering, and the presence of induced and/or natural fractures in such formations. URTeC 1555068
- North America > United States > Colorado (0.71)
- North America > United States > Texas (0.70)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Sabinas - Rio Grande Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Maverick Basin > Eagle Ford Shale Formation (0.99)
- (11 more...)
Summary Mechanical properties play a critical role for optimizing the production from organic-rich shale reservoirs since such reservoirs have extremely low permeability. In situ stress conditions, intrinsic anisotropy due to layering, anisotropy due to fractures, mineral composition, porosity and maturity are among the key parameters affecting the mechanical properties. In this paper, we present experimental results on how Young's modulus, Poisson's ratio, and compressional velocity change with overburden and horizontal stresses for core samples from the oil window of the Eagle Ford shale, Green River immature oil shale and outcrop Mancos shale. These shales have distinct features that are discussed in detail and the intrinsic anisotropy of the shales due to layering is presented. Moreover, challenges in obtaining preserved shale core samples representative of the intact shale formation for the laboratory measurements and associated uncertainties in the laboratory measurements including the effect of natural and coring induced fractures parallel to bedding along with the sample size on the mechanical properties will be discussed. Introduction Mechanical and acoustic properties of shale formations have been investigated for many years as more than seventy percent of the formations drilled are seal shales. Shale formations have been challenging to drill and complete due to the instability of wellbores, mostly attributed to the physico-chemical interaction of clay minerals with drilling fluid, pore pressure build up, temperature and time (Mokhtari and Tutuncu, 2012). Stress concentration around the wellbore could result in shear or tensile failure of rocks. Thus, managing mud weight and salinity of drilling fluids are two major approaches to mitigate wellbore instability. However, the problem is more complicated by the existence of natural fractures and the physics of the osmotic phenomena. URTeC 1619158
- North America > United States > Texas (1.00)
- North America > United States > California > San Francisco County > San Francisco (0.29)
- Geophysics > Borehole Geophysics (0.69)
- Geophysics > Seismic Surveying (0.48)
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- (19 more...)
Summary 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. Introduction As 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. URTeC 1619144
- North America > United States > Colorado (0.51)
- North America > United States > Oklahoma (0.47)
- Research Report > New Finding (0.68)
- Research Report > Experimental Study (0.67)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline (1.00)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Sabinas - Rio Grande Basin > Eagle Ford Shale Formation (0.99)
- North America > United States > Texas > Maverick Basin > Eagle Ford Shale Formation (0.99)
- (8 more...)
Abstract: Improving the recovery of hydrocarbon from shale reservoirs requires incorporation of formation anisotropy into drilling, completion, and hydraulic fracturing operations. In this study, we conducted simultaneous measurements of triaxial deformation and ultrasonic tests on a series of Mancos shale samples collected at various angles to the bedding. The mechanical and acoustic characteristics of the core samples before and after the failure have been studied. The minimum formation strength was obtained for the sample with 60° from the bedding plane. The post-failure radial deformation data as well as the inspection of the failed samples indicate that sliding on the bedding plane has occurred on the core sample with 60° bedding angle. On the other hand, the vertical and horizontal core samples exhibited stepwise failure noticeable on the radial deformation data with steps corresponding to multiple fractures on the recovered cores. The compressional wave velocities have indicated a logarithmic dependence on the axial stress applied. The compressional velocity for the horizontal sample was 30% higher than the velocity for the vertical sample. Finally, the effect of post-failure fracture, confining pressure and residual strength on compressional and shear velocities are discussed.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.68)
- North America > United States > New Mexico > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- North America > United States > Colorado > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- Oceania > Australia > Western Australia > North West Shelf > Roebuck Basin > Bedout Basin > Milne Sandstone Formation (0.98)
- Oceania > Australia > Western Australia > North West Shelf > Roebuck Basin > Bedout Basin > Baxter Sandstone Formation (0.98)