Minh H. Tran

Geomechanics field characterization of woodford Shale and Barnett Shale with advanced logging tools and nano-indentation on drill cuttings

The Woodford Shale and Barnett Shale have emerged as prolific gas plays in the US midcontinent. However, the intrinsically low permeability of these gas shales hinders profitable pro-duction unless horizontal well drilling and multistage hydraulic fracturing are employed. The success of these operations depends on accurate de-terminations of the anisotropic elastic and poroelastic properties of these shale formations.

Outcrop-behind Outcrop (Quarry): Multiscale Characterization of the Woodford Gas Shale, Oklahoma

An outcrop-behind outcrop study was conducted in and adjacent to a 300 100 16 m (980 330 50 ft) quarry of the gas-producing Woodford Shale to structurally/stratigraphically characterize it from the pore to subregional scales using a variety of techniques. Strata around quarry walls were described and correlated to a 64 m (210 ft) long continuous core drilled 150 m (500 ft) back from the quarry wall and almost to the Woodford-Hunton unconformity. Borehole logs obtained include neutron and density porosity (NPHI and DPHI) logs, and logs from Elemental Capture Spectroscopy (ECS™), Combinable Magnetic Resonance (CMR-Plus™), Fullbore Formation MicroImager (FMI™), and sonic scanner (Modular Sonic Imaging Platform, or MSIP™)—all manufactured by Schlumberger. The strata around the quarry are horizontally bedded. Borehole logs were used to identify a basic threefold subdivision into an upper relatively porous quartzose interval; a middle, more clay-rich, and less porous interval; and a lower interval of intermediate quartz-clay content. These intervals correspond to the informally named upper, middle, and lower Woodford. Detailed core and quarry wall description revealed several types of finely laminated lithofacies, with varying amounts of total organic carbon (TOC). The FMI log revealed a much greater degree of variability in laminations than can be readily seen with the naked eye. Organic geochemistry and biomarkers are closely tied to these lithofacies and record cyclic variations in oxic-anoxic depositional environments, which correspond to relative sea level fall-rise cycles. At the scanning electron microscopy scale, microfractures and microchannels are common and provide tortuous pathways for gas (and oil) migration through the shales. Based on FMI and core analysis, fracture density is much greater in the upper quartzose lithofacies than in the lower, more clay-rich lithofacies. A laser imaging detection and ranging (LIDAR) survey around the quarry walls documented two near-vertical fracture trends in the quartzose lithofacies: one striking N85E with spacings of 1.2 m (4 ft) and the other striking N45E related to the present stress field. The FMI analysis only imaged the latter fracture set. Both log-derived and laboratory-tested geomechanical property measurements documented a significant relationship between shale fabric (laminations and preferred clay-particle orientation) and rock strength, and a secondary relationship to mineral composition. Porosity and microfractures or microchannels also appear to influence rock strength. This integrated study has provided insight into the causal relations among Woodford properties at a variety of scales. In particular, a stratigraphic (vertical) segregation of lithofacies can be related to cyclic variations in depositional environments. The resulting stratified zones exhibit variations in their hydrocarbon source and reservoir (fracturable) potential. Such information and predictive capability can be valuable for improved targeted horizontal drilling into enriched source rock and/or readily fracturable reservoir rock in the Woodford and perhaps other gas shales.

Anisotropic Porochemoelectroelastic Solution for an Inclined Wellbore Drilled in Shale

The porochemoelectroelastic analytical models have been used to describe the response of chemically active and electrically charged saturated porous media such as clay soils, shales, and biological tissues. However, existing studies have ignored the anisotropic nature commonly observed on these porous media. In this work, the anisotropic porochemoelectroelastic theory is presented. Then, the solution for an inclined wellbore drilled in transversely isotropic shale formations subjected to anisotropic far-field stresses with time-dependent down-hole fluid pressure and fluid activity is derived. Numerical examples illustrating the combined effects of porochemoelectroelastic behavior and anisotropy on wellbore responses are also included. The analysis shows that ignoring either the porochemoelectroelastic effects or the formation anisotropy leads to inaccurate prediction of the near-wellbore pore pressure and effective stress distributions. Finally, wellbore responses during a leak-off test conducted soon after drilling are analyzed to demonstrate the versatility of the solution in simulating complex down-hole conditions.

Anisotropic Porochemoelectroelastic Solution for Inclined Wellbores with Applications to Operations in Unconventional Shale Plays

In this work, the porochemoelectroelastic theory is applied to analyze instability problems of an inclined wellbore drilled in the laminated and charged saturated chemically active shale formations. Numerical example is given for wellbore drilling in the Woodford gas shale formation. The analysis shows that ignoring either the porochemoelectroelastic effects or the formation anisotropy can lead to inaccurate predictions of potential wellbore integrity problems.

Inclined Direct Shear Testing Device: A New Tool for Bone Mechanics and Osteoporosis Research

Shear properties and strength are crucial for osteoporotic hip and wrist fracture risk assessment. This paper presents the design of a newly developed testing device for bone mechanical properties under circulation of different fluids. The device will ultimately be used to actively modify bone mineral content and porosity to simulate different stages of osteoporosis and directly measure the corresponding changes in mechanical properties. Preliminary results on intact bovine cancellous bones without fluid circulation showed excellent agreement with published literature data.Copyright