The dynamics of hydraulic fracture water confined in nano-pores in shale reservoirs

Hydraulic fracturing treatments and horizontal well technology are central to the success of unconventional oil and gas development. In spite of this success, replicated over several thousand wells over diverse shale plays, hydraulic fracturing for shale wells remains poorly understood. This includes the poor recovery of hydraulic fracture water, the inability to explain the progressive increases in produced water salinity and an incomplete understanding of the potential trapping mechanisms for hydraulic fracture water. In this work, we focus on describing the distribution of saline water in organic and inorganic pores as a function of pore size and pore morphology with the purpose of providing fundamental insights into above questions. A kerogen model is constructed by mimicking the maturation process in a molecular dynamics simulator and it incorporates structural features observed in SEM images including the surface roughness, tortuous paths, material disorder and imperfect pore openings of kerogen pores. This work also extends this kerogen model through the use of oxygenated functional groups to study fluid behavior in partially mature shales associated with non-zero oxygen to carbon ratios. Our results demonstrate that water entrapment mechanism and the distribution of water and ions in organic and inorganic pores are strongly related to the pore-surface mineralogy and pore width. The work in this paper also underscores the importance of kerogen thermal maturity and pore roughness on the accessibility of the kerogen material to water

Persistently Elevated HBV Viral-Host Junction DNA in Urine as a Biomarker for Hepatocellular Carcinoma Minimum Residual Disease and Recurrence: A Pilot Study

Hepatitis B virus (HBV)-host junction sequences (HBV-JSs) has been detected in the urine of patients with HBV infection. This study evaluated HBV-JSs as a marker of minimum residual disease (MRD) and tumor recurrence after treatment in HBV-hepatocellular carcinoma (HCC) patients. Archived serial urine DNA from two HBV–HCC with recurrence as confirmed by MRI and four HBV-related cirrhosis (LC) patients were used. Urinary HBV-JSs were identified by an HBV-targeted NGS assay. Quantitative junction-specific PCR assays were developed to investigate dynamic changes of the most abundant urinary HBV-JS. Abundant urinary HBV-JSs were identified in two cases of tumor recurrence. In case 1, a 78-year-old female with HBV- HCC underwent a follow-up MRI following microwave ablation. While MRI results were variable, the unique HBV-JS DNA, HBV-Chr17, steadily increased from initial diagnosis to HCC recurrence. In case 2, a 74-year-old male with HBV–HCC contained two HBV-JS DNA, HBV-Chr11 and HBV-TERT, that steadily increased after initial HCC diagnosis till recurrence. One LC examined had HBV-TERT DNA detected, but transiently in 3.5 years during HCC surveillance. HBV-JS DNA was persistently elevated prior to the diagnosis of recurrent HCC, suggesting the potential of urinary HBV-JS DNA to detect MRD and HCC recurrence after treatment

Congenital Diarrhea and Cholestatic Liver Disease: Phenotypic Spectrum Associated with MYO5B Mutations.

Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic findings that requires life-long parenteral nutrition or intestinal transplantation. A large number of such patients eventually develop cholestatic liver disease. Bi-allelic MYO5B mutations are also identified in a subset of patients with predominant early-onset cholestatic liver disease. We present here the compilation of 114 patients with disease-causing MYO5B genotypes, including 44 novel patients as well as 35 novel MYO5B mutations, and an analysis of MYO5B mutations with regard to functional consequences. Our data support the concept that (1) a complete lack of MYO5B protein or early MYO5B truncation causes predominant intestinal disease (MYO5B-MVID), (2) the expression of full-length mutant MYO5B proteins with residual function causes predominant cholestatic liver disease (MYO5B-PFIC), and (3) the expression of mutant MYO5B proteins without residual function causes both intestinal and hepatic disease (MYO5B-MIXED). Genotype-phenotype data are deposited in the existing open MYO5B database in order to improve disease diagnosis, prognosis, and genetic counseling

Characteristics of electron traps in Si-doped Ga0.51In0.49P and electrical properties of modulation doped GaInP/InGaAs/GaAs heterostructures

In order to investigate the feasibility of Si-doped Ga0.51In0.49P for modulation-doped field effect transistor applications, single Ga0.51In0.49P llayers and Ga0.51In0.49P/InxGa1-xAs/GaAs (x = 0, 0.15 and 0.25) modulation doped heterostructures grown by gas source molecular beam epitaxy were characterized through deep level transient spectroscopy and Hall-effect measurements. Electrical characterization of the undoped and moderately Si-doped (N-D = 3 x 10(17) cm(-3)) GaInP layers yielded an electron trap with an activation energy of 0.75 eV and a temperature dependent capture cross section with a capture barrier of 0.593 eV. The density of this trap increased, and an anomalous decrease in the free carrier concentration of GaInP was observed after the samples were annealed at temperatures typically used in device processing. While, this trap showed characteristics similar to DX centers, it was not detected in highly Si doped (N-D approximate to 4 x 10(18) cm(-3)) as grown layers suggesting that the trap is a defect complex including a residual impurity. While very high two-dimensional electron gas density (2.6 x 10(12) cm(-2) at 30 K) was achieved in the lattice matched (x = 0) structures, the strained structures were found to be very sensitive to heat treatment, although the InGaAs layers thicknesses were below the theoretical critical thickness. Persistent photoconductivity and a significant reduction in the interface sheet electron density were observed after annealing. The anomalous behavior can be attributed to the decrease in the carrier concentration of the doped GaInP barrier layer and to the strain relaxation at the hetero-interface after annealing. While other explanations may be possible, the decrease in the GaInP electron concentration can be attributed to Si atoms moving from donor to acceptor sites. (C) 1998 Elsevier Science S.A. All rights reserved

Feasibility of the GaInP/InGaAs/GaAs system for modulation doped field-effect transistors

Si-doped single Ga0.51In0.49P layers and GaInP/InGaAs/GaAs modulation doped field-effect transistor structures grown by gas source molecular beam epitaxy were characterized in detail through Hall-Effect and Deep Level Transient Spectroscopy techniques. Electrical characterization of the undoped and moderately Si-doped (ND = 3 x 1017 cm-3) GaInP layers yielded an electron trap with an activation energy of 0.75 eV and a temperature dependent capture cross section with a capture barrier of 0.593 eV showing DX center properties. The trap was not detected in highly Si doped (ND = 4 x 1018 cm-3) as grown layers suggesting that it is a defect complex including a residual impurity. An anomalous decrease in the free carrier concentration of GaInP was observed after the samples were annealed at temperatures typically used in device processing. While other explanations may be possible, this can be attributed to Si atoms moving from donor to acceptor sites. Very high two-dimensional electron gas density (2.6 x 1012 cm-2 at 30 K) was achieved in the lattice matched (x = 0) structure. The strained structures were found to be very sensitive to heat treatment and another level with dislocation trap characteristics was detected in these structures. Persistent photoconductivity and a significant reduction in the interface sheet electron density were observed in the strained samples after annealing. This can partly be attributed to the strain relaxation at the heterointerface. With no detectable traps in heavily Si-doped GaInP and with very high two dimensional electron gas densities, GaInP/InGaAs/GaAs seems to be a promising material system for modulation doped field-effect transistor applications

Microscopic Dynamics of Water and Hydrocarbon in Shale-Kerogen Pores of Potentially Mixed-Wettability

Distribution of alkanes and water in organic pores of shale, referred to as kerogen, is essential information required for estimation of shale-reservoir oil- and gas-in-place, adsorption of hydrocarbon, and fate of frac-water. A practical modeling approach is presented for proper description of the kerogen pore systems with different mixed wettability, surface roughness, tortuous paths, and material disorder. Three kerogen models, namely activated kerogen, kerogen free of active sites, and grapheme-slit pore, with proper surface-oxidized functional groups and high-temperature-and-pressure maturation, are constructed by simulation. Distribution of octane and water in the organic pores of these models is predicted by molecular dynamics simulation. Comparison of results reveals the importance of accurate characterization of kerogen pore systems by particular pore morphology, surface activation, and pore size. The improved kerogen models provided here are shown to determine the placement, distribution, and trapping of frac-water in shale depending on the maturity of the kerogen within organic-rich shales. Copyright 2013, Society of Petroleum Engineers

A Pore Scale Study Describing the Dynamics of Slickwater Distribution in Shale Gas Formations Following Hydraulic Fracturing

Hydraulic fracturing with slickwater to stimulate shale gas wells is routinely employed to enable increased contact with larger reservoir volumes and has the advantages of lower cost, the ability to create larger and more complex fractures, less formation damage and easier cleanup. However, a common observation is that during flow back only 10 to 20% of the frac water is recovered, even though a typical stimulation job requires several million gallons of water. Although there have been some attempts to address this phenomenon, the associated theories are lacking in scientific rigor. Due to the nanoporous nature of shales where pore proximity effects and strong inter-molecular interactions may dominate, a fundamental pore-level analysis is employed in this work to better understand and leverage the dynamics of the physiochemical processes during and after fracturing. By varying pore size in organic and inorganic pores in shales, we study the dynamics of water and gas molecules, as well as that of ions. The results of our study demonstrate that the mechanics of water entrapment and the water and ions distribution are strongly linked to the pore-surface mineralogy. Understanding the placement and distribution of frac water in both organic and inorganic pores in shales will potentially help in improved forecasting of well performance and address concerns related to the contamination of groundwater resources. Copyright 2013, Society of Petroleum Engineers

Gas source molecular beam epitaxy growth and characterization of Ga0.51In0.49P/InxGa1-xAs/GaAs modulation-doped field-effect transistor structures

Lattice-matched Ga0.51In0.49P/GaAs and strained Ga0.51In0.49P/InxGa1-xAs/GaAs (0.1 less than or equal to x less than or equal to 0.25) modulation-doped field-effect transistor structures were grown by gas source molecular beam epitaxy by using Si as dopant. Detailed electrical characterization results are presented, The Ga0.5In0.49P/In0.25Ga0.75As/GaAs sample yielded dark two-dimensional electron gas densities of 3.75 x 10(12) cm(-2) (300 K) and 2.3 x 10(12) cm(-2) (77 K) which are comparable to the highest sheet electron densities reported in AlGaAs/InGaAs/GaAs and InAlAs/InGaAs/InP modulation-doped heterostructures. Persistent photoconductivity was observed in the strained samples only. A 0.797 eV deep lever has been detected in the undoped GaInP layers of the structures. Another lever, with DLTS peak height dependent an the filling pulse width, has been detected at the interface of the strained samples. Based on the DLTS and Hall effect measurement results, this level, which seems to be the origin of persistent photoconductivity, can be attributed to the strain relaxation related defects