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36

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Introduction

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## Publications

Publications (36)

In recent years, complex well explorations have moved into more challenging environments (ultra-deep, high-pressure/high-temperature (HPHT), extended reach laterals). These environments require a closely integrated and multidisciplinary process to ensure efficiency and mitigate risk. In particular, the process of perforating has called for careful...

Perforated completions play a crucial role in efficient hydrocarbon recovery as well as long-term well productivity. However, perforating often alters formation permeability around the perforation tunnel, which along with other perforation parameters (penetration, hole size, and shot configuration) significantly impacts near-wellbore pressure drop,...

The distributed nature of fiber-optic measurements such as distributed temperature sensing (DTS), distributed acoustic sensing (DAS), and distributed strain sensing (DSS) enables nearly continuous monitoring of the downhole environment in both space and time. Though continuous monitoring opens the door to a rich new set of asset management applicat...

Given the near ubiquity of fiber-optic, information and communication technologies in reservoir and well management, there is a significant need for one-stop shop downhole distributed sensing data analysis methods together with machine learning techniques towards autonomous analysis of such data sources. However, traditional approaches of convertin...

A truly optimized completion requires a wide range of understanding and activities. Starting with a thorough understanding of the reservoir, each completion element must be fully addressed from connecting to the reservoir, to enhancing the reservoir through proper treatments, to conducting hydrocarbons to surface for optimal efficiency. By consider...

Shaped charge jet perforation is the most widely used method for establishing hydraulic communication between the formation and the wellbore. A primary objective of this method is to create "clean" tunnels that can efficiently transport hydrocarbons. However, during the perforating event, the detonation of the explosive charge inevitably compresses...

Large-diameter, long-interval tubing conveyed perforation (TCP) operations are an important part of modern deepwater completion design. Safe and cost-effective designs require an understanding of the interdependence between a large set of static and dynamic parameters that characterize the downhole processes affecting a complex well completion. Typ...

As the Oil and Gas industry looks forward to perforating next-generation complex wells (including but not limited to HPHT, deepwater, geothermal, multi-stage long horizontals etc.), computational modeling tools have been increasingly used to predict the transient flow physics that govern the design and optimization of perforating jobs. In particula...

Perforated completions have become a standard process of well completions, where the wellbore is connected to the reservoir by perforating the casing/cement wall and the formation to provide flow paths through which formation fluids can enter the wellbore. This flow path (defined by the perforation tunnel) is usually encompassed by drilling damage,...

Large-diameter, long-interval tubing-conveyed perforation (TCP) operations are an important part of modern deepwater completion designs. Perforation jobs typically place a large dynamic load on the downhole equipment. Predicting the magnitude and transient behavior of such loads is a critical step in developing completion designs that avoid damage...

We present our results from testing 15 x 15 x 10 mm(3) CdZnTe pixelated detectors using a readout system based on the H3D ASIC. Data obtained with an uncollimated Cs-137 source helped reveal details of the operational principle of such devices, and how the pulse-processing electronics may influence their performance. The responses of individual pix...

Perforation operations are an important part of the well completion process in many field developments today. However, there are two considerations paramount to such a design. First, the post-job well production rate depends critically on a complex system in which the formation, perforations, and wellbore are dynamically and nonlinearly coupled tog...

We experimentally investigate the possible correlation between high hole-trap concentrations in wide-bandgap semiconductors and delayed temporal response of high-flux x-ray detector devices to changing photon fluxes. We show that fast photo-current response can be achieved with (1) CdZnTe detectors with high hole mobility-lifetime products, (2) tem...

Recently, homogenization theory based on a multiple-scale perturbation of the electron transport equation has been used to derive a mathematical framework for modeling the excess charge lost to Te inclusions within radiation detectors based on semi-insulating cadmium zinc telluride (CdZnTe). In that theory, the heterogeneous material is mathematica...

Under intense x-ray irradiation, wide band gap semiconductor radiation detectors fabricated from crystals with low hole transport properties develop a steady-state space charge distribution that results from a dynamic equilibrium between charge carrier dynamics and the incident photon field. At a high enough x-ray flux, this space charge can collap...

A semi-analytic approximation to the weighting potential within monolithic pixelated CdZnTe radiation detectors is presented. The approximation is based on solving the multi-dimensional Laplace equation that results upon replacing rectangular pixels with equal-area circular pixels. Further, we utilize the simplicity of the resulting approximate wei...

In this paper, homogenization theory based on a multiple scale perturbation of the charge-transport equation is used to derive a mathematical framework for modeling the cumulative effect of Te inclusions in radiation detectors based on semi-insulating cadmium zinc telluride (CdZnTe). The derived framework naturally incorporates a wide range of phys...

The transport, trapping, and subsequent detrapping of charge in single crystals of semi-insulating cadmium zinc telluride
(CdZnTe) has been analyzed using multiple-scale perturbation techniques. This method has the advantage of not only treating
impulse charge generation typical in spectroscopic analysis, but also a large class of continuous genera...

It has been observed that pixillated CdZnTe detectors fabricated from crystals with low hole transport properties (μ<sub>h</sub>τ<sub>h</sub>≪10<sup>-5</sup> cm <sup>2</sup> V <sup>-1</sup>) experience a dynamic lateral polarization when exposed to a high flux of x-rays. In this effect, counts are transferred from pixels near the edge of the irradi...

In this paper, we theoretically investigate the mechanism of polarization in wide-bandgap semiconductor radiation detectors under high-flux x-ray irradiation. Our general mathematical model of the defect structure within the bandgap is a system of balance laws based on carrier transport and defect transition rates, coupled together with the Poisson...

The dynamic lateral polarization and charge steering effect was studied in 2D pixilated CdZnTe monolithic detector arrays designed for high flux X-ray imaging applications. While these detectors have shown the ability to work at 15 times 10<sup>6</sup> counts s<sup>-1</sup> mm<sup>-2</sup> and higher count-rates in pulse mode, we observed some dete...

The performance of 2-D CdZnTe monolithic detector arrays designed for high flux X-ray imaging applications was studied. For the first time we have obtained 5 times 10<sup>6</sup> counts/s/mm<sup>2</sup> count-rate for a CdZnTe pixelated detector array. This count-rate is more than twice the highest count-rate ever achieved using a CdZnTe detector a...

We report on the material selection, testing and fabrication technology development of high performance CdZnTe quasi-hemispherical CAPture (TM) Plus radiation detectors. Quasi-hemispherical CdZnTe detectors offer a cost effective alternative to other single-polarity (electron-only) detector configurations such as co-planar grid, pixilated or Frisch...

In this paper we report on the simulation, design, and testing of high performance CdZnTe quasi-hemispherical CAPture (TM) Plus radiation detectors. Quasi-hemispherical CdZnTe detectors offer a cost effective alternative to other single-polarity (electron-only) detector configurations such as co-planar grid, pixilated or Frish ring CdZnTe detectors...

An extension of the wave propagation algorithm first introduced by LeVeque [J. Comput. Phys. 131 (1997) 327] is developed for hyperbolic systems on a general curved manifold. This extension is important in a variety of applications, including the propagation of sound waves on a curved surface, shallow water flow on the surface of the Earth, shallow...

We study a general approach to solving conservation laws of the form qt+f(q,x)x=0, where the flux function f(q,x) has explicit spatial variation. Finite-volume methods are used in which the flux is discretized spatially, giving a function fi(q) over the ith grid cell and leading to a generalized Riemann problem between neighboring grid cells. A hig...

Thesis (Ph. D.)--University of Washington, 2002 Many interesting physical systems are successfully modeled with time-dependent hyperbolic conservation laws on smooth manifolds. Examples of such systems include classical hydrodynamic flows in non-trivial geometry that are important in aerodynamic modeling, or the structure of shallow water flow on t...

We describe a mechanism which can cause crossflow instabilities in the approximation of multidimensional detonation waves. Crossflow instabilities can grow if a discontinuity is nearly aligned with the mesh and if the velocity transverse to the discontinuity is close to zero. When these conditions are met a continuous perturbation of the constant s...

We apply first order hyperbolic formalisms for the Einstein equations similar to that of Bona et al. (Phys. Rev. D 56, 3404 (1997)) to a 1D non-linear plane wave. The lapse function is algebraically related to the spatial metric, alpha = Q(xi,t) h^{1/2}, rather than being part of the hyperbolic system. With this choice of lapse and a suitable choic...

. An inhomogeneous system of conservation laws will exhibit steady solutions when flux gradients are balanced by source terms. These steady solutions are difficult for many numerical methods (e.g., fractional step methods) to capture and maintain. Recently, a quasi-steady wave-propagation algorithm was developed and used to compute near-steady shal...

The collision of a solitary wave, travelling over a horizontal
bed,
with a vertical wall
is investigated using a boundary-integral method to compute the potential
fluid flow
described by the Euler equations. We concentrate on reporting new results
for
that part of the motion when the wave is near the wall. The wall residence
time,
i.e. th...