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Seismic Determination of Reservoir Heterogeneity: Application to the Characterization of Heavy Oil Reservoirs

Description: The objective of the project was to examine how seismic and geologic data could be used to improve characterization of small-scale heterogeneity and their parameterization in reservoir models. Performed a theoretical and numerical study to examine which subsurface features the surface seismic method actually resolves.
Date: March 12, 2003
Creator: Imhof, Matthias G. & Castle, James W.
Partner: UNT Libraries Government Documents Department

Low-frequency asymptotic analysis of seismic reflection from afluid-saturated medium

Description: Reflection of a seismic wave from a plane interface betweentwo elastic media does not depend on the frequency. If one of the mediais poroelastic and fluid-saturated, then the reflection becomesfrequency-dependent. This paper presents a low-frequency asymptoticformula for the reflection of seismic plane p-wave from a fluid-saturatedporous medium. The obtained asymptotic scaling of the frequency-dependentcomponent of the reflection coefficient shows that it is asymptoticallyproportional to the square root of the product of the reservoir fluidmobility and the frequency of the signal. The dependence of this scalingon the dynamic Darcy's law relaxation time is investigated as well.Derivation of the main equations of the theory of poroelasticity from thedynamic filtration theory reveals that this relaxation time isproportional to Biot's tortuosity parameter.
Date: April 14, 2004
Creator: Silin, D.B.; Korneev, V.A.; Goloshubin, G.M. & Patzek, T.W.
Partner: UNT Libraries Government Documents Department

A hydrologic view on Biot's theory of poroelasticity

Description: The main objective of this work is to obtain a simplified asymptotic representation of the reflection of seismic signal from a fluid-saturated porous medium in the low-frequency domain. In the first part, we derive the equations of low-frequency harmonic waves in a fluid-saturated elastic porous medium from the basic concepts of filtration theory. We demonstrate that the obtained equations can be related to the poroelasticity model of Frenkel-Gassmann-Biot, and to pressure diffusion model routinely used in well test analysis as well. We thus try to put the poroelastic and filtration theories on the same ground. We study the reflection of a low-frequency signal from a plane interface between elastic and elastic fluid-saturated porous media. We obtain an asymptotic scaling of the frequency-dependent component of the reflection coefficient with respect to a dimensionless parameter depending on the frequency of the signal and the reservoir fluid mobility. We also investigate the impact of the relaxation time and tortuosity on this scaling.
Date: January 13, 2004
Creator: Silin, D.B.; Korneev, V.A.; Goloshubin, G.M. & Patzek, T.W.
Partner: UNT Libraries Government Documents Department

Coupled reservoir-geomechanical analysis of the potential fortensile and shear failure associated with CO2 injection in multilayeredreservoir-caprock systems

Description: Coupled reservoir-geomechanical simulations were conductedto study the potential for tensile and shear failure e.g., tensilefracturing and shear slip along pre-existing fractures associated withunderground CO2 injection in a multilayered geological system. Thisfailure analysis aimed to study factors affecting the potential forbreaching a geological CO2 storage system and to study methods forestimating the maximum CO2 injection pressure that could be sustainedwithout causing such a breach. We pay special attention to geomechanicalstress changes resulting from upward migration of the CO2 and how theinitial stress regime affects the potential for inducing failure. Weconclude that it is essential to have an accurate estimate of thethree-dimensional in situ stress field to support the design andperformance assessment of a geological CO2 injection operation. Moreover,we also conclude that it is important to consider mechanical stresschanges that might occur outside the region of increased reservoir fluidpressure (e.g., in the overburden rock) between the CO2-injectionreservoir and the ground surface.
Date: March 27, 2007
Creator: Rutqvist, J.; Birkholzer, J.T. & Tsang, C.-F.
Partner: UNT Libraries Government Documents Department


Description: The ''Drift Shadow'' is defined as the relatively drier region that forms below subsurface cavities or drifts in unsaturated rock. Its existence has been predicted through analytical and numerical models of unsaturated flow. However, these theoretical predictions have not been demonstrated empirically to date. In this project they plan to test the drift shadow concept through field investigations and compare our observations to simulations. Based on modeling studies they have an identified suitable site to perform the study at an inactive mine in a sandstone formation. Pretest modeling studies and preliminary characterization of the site are being used to develop the field scale tests.
Date: January 15, 2006
Creator: G. W. Su, T. J. Kneafsey, T. A. Ghezzehei, B. D. Marshall, and P. J. Cook
Partner: UNT Libraries Government Documents Department

An asymptotic model of seismic reflection from a permeable layer

Description: Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot's model of poroelasticity. A review of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and Darcy's law suggests an alternative new physical interpretation of some coefficients of the classical poroelasticity. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The absolute value of this parameter is equal to the product of the kinematic reservoir fluid mobility and the wave frequency. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). Practical applications of the obtained asymptotic formulae are seismic modeling, inversion, and at-tribute analysis.
Date: October 15, 2009
Creator: Silin, D. & Goloshubin, G.
Partner: UNT Libraries Government Documents Department

Massively parallel electrical conductivity imaging of the subsurface: Applications to hydrocarbon exploration

Description: Three-dimensional (3D) geophysical imaging is now receiving considerable attention for electrical conductivity mapping of potential offshore oil and gas reservoirs. The imaging technology employs controlled source electromagnetic (CSEM) and magnetotelluric (MT) fields and treats geological media exhibiting transverse anisotropy. Moreover when combined with established seismic methods, direct imaging of reservoir fluids is possible. Because of the size of the 3D conductivity imaging problem, strategies are required exploiting computational parallelism and optimal meshing. The algorithm thus developed has been shown to scale to tens of thousands of processors. In one imaging experiment, 32,768 tasks/processors on the IBM Watson Research Blue Gene/L supercomputer were successfully utilized. Over a 24 hour period we were able to image a large scale field data set that previously required over four months of processing time on distributed clusters based on Intel or AMD processors utilizing 1024 tasks on an InfiniBand fabric. Electrical conductivity imaging using massively parallel computational resources produces results that cannot be obtained otherwise and are consistent with timeframes required for practical exploration problems.
Date: June 1, 2009
Creator: Newman, G.A. & Commer, M.
Partner: UNT Libraries Government Documents Department


Description: Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. But while the volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade, it is not yet possible to make use of all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. The goal of this project is to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem is necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management. Facies (defined here as regions of relatively uniform petrophysical properties) are common features of all reservoirs. Because the flow properties of the various facies can vary greatly, knowledge of the location of facies boundaries is of utmost importance for the prediction of reservoir performance and for the optimization of reservoir management. When the boundaries between facies are fairly well known, but flow properties are poorly known, the average properties for all facies can be determined using traditional techniques. Traditional history matching honors dynamic data by adjusting petrophysical properties in large areas, but in the process of adjusting the reservoir model ignores the static data and often results in implausible reservoir models. In general, ...
Date: January 1, 2003
Creator: Reynolds, Albert C.; Oliver, Dean S.; Zhang, Fengjun; Dong, Yannong; Skjervheim, Jan Arild & Liu, Ning
Partner: UNT Libraries Government Documents Department

Energetics of melts from thermal diffusion studies. Final report

Description: Most processes in geology are a consequence at some level of the flow of energy or mass. Heat conduction and chemical diffusion are examples of two of these sorts of flows which are driven by temperature and chemical potential imbalances, respectively. In the general case these flows may be coupled so that, for instance, a temperature gradient may result in a flow of mass as well as heat. This effect in liquids was demonstrated by Soret (1879) and bears his name. In gases or solids the phenomenon is given the general name thermal diffusion. It was the purpose of this research program to examine the Soret effect in molten silicates under laboratory conditions. Results of these experiments are used to evaluate the form and quantitative values of many thermodynamic and kinetic properties of silicate melts over a range of temperature, pressure, and bulk composition. The author published a comprehensive review and synthesis with a microscopic theoretical explanation for the effect at low pressure in silicate liquids of geological interest. He conducted experimental investigations of molecular diffusion in the absence of a thermal gradient through experiments involving dissolution of solid silicates in molten silicate and interdiffusion of species between miscible silicate liquids. Collectively these results enable the author to construct a more comprehensive model of molecular diffusion in magmatic liquids. He has applied this model to problems of magma mixing and crustal assimilation.
Date: December 1, 1998
Creator: Lesher, C.E.
Partner: UNT Libraries Government Documents Department

Identifying structures in clouds of induced microseismic events

Description: A method for finding improved relative locations of microearthquakes accompanying fluid production and injection is presented. The method is based on the assumption that the microearthquake locations are more clustered than found when events are located using conventional techniques. By allowing the rms misfit between measured arrival times and predicted arrival times to increase if events move closer together, the authors find that there is more structure in the pattern of seismic locations. The method is demonstrated using a dataset of microearthquakes induced by hydraulic fracturing. The authors find that structures found using relative arrival times of events having similar waveforms to find improved relative locations of events can also be recovered using the new inversion method but without the laborious repicking procedure. The method provides improved relative locations and hence, an improved image of the structure within the seismic zone that may allow for a better relation between microearthquake locations and zones of increased fluid permeability to be found.
Date: July 1, 1997
Creator: Fehler, M.; House, L. & Phillips, W.S.
Partner: UNT Libraries Government Documents Department

Time Scaling of the Rates of Produced Fluids in Laboratory Displacements

Description: In this report, the use of an asymptotic method, based on the time scaling of the ratio of produced fluids, to infer the relative permeability exponent of the displaced phase near its residual saturation, for immiscible displacements in laboratory cores was proposed. Sufficiently large injection rates, the existence of a power law can be detected, and its exponent inferred, by plotting in an appropriate plot the ratio of the flow rates of the two fluids at the effluent for some time after breakthrough.
Date: February 27, 2001
Creator: Laroche, Catherine; Chen, Min; Yortsos, Yanis C. & Kamath, Jairam
Partner: UNT Libraries Government Documents Department

Advanced Techniques for Reservoir Simulation and Modeling of Non-Conventional Wells

Description: This project targets the development of (1) advanced reservoir simulation techniques for modeling non-conventional wells; (2) improved techniques for computing well productivity (for use in reservoir engineering calculations) and well index (for use in simulation models), including the effects of wellbore flow; and (3) accurate approaches to account for heterogeneity in the near-well region.
Date: August 28, 2000
Creator: Durlofsky, Louis J.
Partner: UNT Libraries Government Documents Department

The Shape of a Gravity Finger

Description: A new gravity finger model was proposed in this report in the absence of interfacial tension but in the presence of gravities. This model considered differences in density and viscosity of the two fluids. Thus, it was able to represent both stable and unstable displacements, and the finger development along either the upper or the bottom walls of a channel. This solution recovers the Saffman - Taylar solution if gravity is neglected. The results of the solution are very similar to the solutions proposed by Brener et al. for the gravity number up to 10. The solution provided in this work only has one free parameter while the solution of Brener et al. has three.
Date: September 11, 2000
Creator: Zhan, Lang & Yortsos, Yanis
Partner: UNT Libraries Government Documents Department

Development and Application of a Paleomagnetic/Geochemical Method for Constraining the Timing of Burial Diagenetic and Fluid

Description: Studies of diagenesis caused by fluid migration or other events are commonly hindered by a lack of temporal control. Our results to date demonstrate that a paleomagnetic/geochemical approach can be used to date fluid migration as well as burial diagenetic events. Our principal working hypothesis is that burial diagenetic processes (e.g., maturation of organic-rich sediments and clay diagenesis) and the migration of fluids can trigger the authigenesis of magnetic mineral phases. The ages of these events can be constrained by comparing chemical remanent magnetizations (CRMs) to independently established Apparent Polar Wander Paths. While geochemical (e.g. stable isotope and organic analyses) and petrographic studies provide important clues for establishing these relationships, the ultimate test of this hypothesis requires the application of independent dating methods to verify the paleomagnetic ages. Towards this end, we have used K-Ar dating of illitization as an alternative method for constraining the ages of magnetic mineral phases in our field areas.
Date: March 10, 2005
Creator: Elmore, Richard D. & Engel, Michael H.
Partner: UNT Libraries Government Documents Department


Description: We are now entering the final stages of our ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342). We have now developed several techniques to help distinguish economic hydrocarbon deposits from false ''Fizz'' gas signatures. These methods include using the proper in situ rock and fluid properties, evaluating interference effects on data, and doing better constrained inversions for saturations. We are testing these techniques now on seismic data from several locations in the Gulf of Mexico. In addition, we are examining the use of seismic attenuation as indicated by frequency shifts below potential reservoirs. During this quarter we have: Began our evaluation of our latest data set over the Neptune Field; Developed software for computing composite reflection coefficients; Designed and implemented stochastic turbidite reservoir models; Produced software & work flow to improve frequency-dependent AVO analysis; Developed improved AVO analysis for data with low signal-to-noise ratio; and Examined feasibility of detecting fizz gas using frequency attenuation. Our focus on technology transfer continues, both by generating numerous presentations for the upcoming SEG annual meeting, and by beginning our planning for our next DHI minisymposium next spring.
Date: August 12, 2005
Creator: Batzle, Michael; Han, D-h; Gibson, R. & James, Huw
Partner: UNT Libraries Government Documents Department

A Study of the Effect of Mobility Ratios on Pattern Displacement Behavior and Steamlines to Infer Permeability Media, SUPRI TR-115

Description: Pattern geometry plays a major role in determining oil recovery during secondary and enhanced oil recovery operations. Although simulation is an important tool for design and evaluation, the first step often involves rough calculations based upon areal sweep efficiencies of displacements in homogeneous, two-dimensional, scaled, physical models. These results are available as a function of the displacement pattern and the mobility ratio, M. The mobility ratio is simply the mobility of the displacing phase over that of the displaced, or resident, phase. Because it is possible to compute sweep efficiency analytically when the displacing and displaced phase have the same mobility, scaled physical model results have been verified for unit mobility ratios.
Date: August 9, 1999
Creator: Brigham, William E.; Kovscek, Anthony R. & Wang, Yuandong
Partner: UNT Libraries Government Documents Department

Preliminary estimates of electrical generating capacity of slim holes--a theoretical approach

Description: The feasibility of using small geothermal generators (< 1 MWe) for off-grid electrical power in remote areas or for rural electrification in developing nations would be enhanced if drilling costs could be reduced. This paper examines the electrical generating capacity of fluids which can be produced from typical slim holes (six-inch diameter or less), both by binary techniques (with downhole pumps) and, for hotter reservoir fluids, by conventional spontaneous-discharge flash-steam methods. Depending mainly on reservoir temperature, electrical capacities from a few hundred kilowatts to over one megawatt per slim hole appear to be possible.
Date: January 26, 1995
Creator: Pritchett, John W.
Partner: UNT Libraries Government Documents Department

Component-Based Framework for Subsurface Simulations

Description: Simulations in the subsurface environment represent a broad range of phenomena covering an equally broad range of scales. Developing modelling capabilities that can integrate models representing different phenomena acting at different scales present formidable challenges both from the algorithmic and computer science perspective. This paper will describe the development of an integrated framework that will be used to combine different models into a single simulation. Initial work has focused on creating two frameworks, one for performing smooth particle hydrodynamics (SPH) simulations of fluid systems, the other for performing grid-based continuum simulations of reactive subsurface flow. The SPH framework is based on a parallel code developed for doing pore scale simulations, the continuum grid-based framework is based on the STOMP (Subsurface Transport Over Multiple Phases) code developed at PNNL. Future work will focus on combining the frameworks together to perform multiscale, multiphysics simulations of reactive subsurface flow.
Date: August 1, 2007
Creator: Palmer, Bruce J.; Fang, Yilin; Hammond, Glenn E. & Gurumoorthi, Vidhya
Partner: UNT Libraries Government Documents Department

The Bulalo geothermal reservoir Makiling-Banahao area, Philippines

Description: The Bulalo field, located within the Makiling-Banahao geothermal prospect, is being explored and developed by Philippine Geothermal Incorporated (PGI), a branch of the Union Oil Company of California. During the past four years, twenty-eight wells have been drilled and completed in the Bulalo heat anomaly. These wells have defined a large geothermal reservoir characterized by a high-temperature effluent which can be spontaneously produced to generate commercial power. An extensive flow testing program has resulted in the production of over thirteen billion pounds of reservoir effluent. After flashing the steam to atmospheric conditions, nearly seven billion pounds of produced reservoir fluid have been reinjected into the Bulalo reservoir. In spite of the large quantity of reservoir effluent that has been produced and reinjected, insufficient testing has been conducted to determine the total commercial power generating capacity of this large liquid-dominated reservoir. The preliminary estimate of generating capacity has led to the current installation of 220 MW. Field development for the installation of four 55 MW units is in progress. The initial 55 MW unit is scheduled for operation in July, 1979, with Unit 2 to operate in the four quarter of 1979. Continued drilling and production testing up to the initiation of commercial operation will afford periodic reserve updating and confirmation for additional power generating units. After commercial power generation commences, data will be available to establish a more reliable estimate of the Bulalo field potential.
Date: January 1, 1978
Creator: Messer, Philip H. & de las Alas, Val
Partner: UNT Libraries Government Documents Department


Description: The boundaries of reservoir fluid convection cells are discreet and intricate zones, commonly sealed or reduced in permeabilities, which are often quite readily identifiable in many hydrothermal systems. Cell boundaries in the Geysers Steam Field are more vague; however, they are gradually being revealed by cumulative and extensive wellbore data. A profound example of a type of boundary has been revealed by drilling in one area of the steam field. A proposed model utilizes a sericitic alteration scheme to establish cell self-sealing. Mineralogical, permeability, and temperature properties all coincide so as to allow formation of a boundary model. This reinforces previously held views that the reservoir cell rock and hydrothermal system are greatly out of equilibrium. Such similar phenomena are suggested from drilling experiences in other parts of the steam field. Considerably, more work is required to better define and comprehend the nature and location of reservoir cell boundaries within the Geysers Steam Field.
Date: January 22, 1985
Creator: Hebein, J.L.
Partner: UNT Libraries Government Documents Department

Temporal changes in noble gas compositions within the Aidlinsector ofThe Geysers geothermal system

Description: The use of nonreactive isotopic tracers coupled to a full thermal-hydrological reservoir simulation allows for an improved method of investigating how reservoir fluids contained within matrix and fractures contribute over time to fluids produced from geothermal systems. A combined field and modeling study has been initiated to evaluate the effects of injection, production, and fracture-matrix interaction on produced noble gas contents and isotopic ratios. Gas samples collected periodically from the Aidlin steam field at The Geysers, California, between 1997 and 2006 have been analyzed for their noble gas compositions, and reveal systematic shifts in abundance and isotopic ratios over time. Because of the low concentrations of helium dissolved in the injection waters, the injectate itself has little impact on the helium isotopic composition of the reservoir fluids over time. However, the injection process may lead to fracturing of reservoir rocks and an increase in diffusion-controlled variations in noble gas compositions, related to gases derived from fluids within the rock matrix.
Date: May 3, 2006
Creator: Dobson, Patrick; Sonnenthal, Eric; Kennedy, Mack; van Soest,Thijs & Lewicki, Jennifer
Partner: UNT Libraries Government Documents Department

Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs

Description: During this last quarter of the ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342), our efforts have become focused on technology transfer. To this end, we completing our theoretical developments, generating recommended processing flows, and perfecting our rock and fluid properties interpretation techniques. Some minor additional data analysis and modeling will complete our case studies. During this quarter we have: Presented findings for the year at the DHI/FLUIDS meeting at UH in Houston; Presented and published eight papers to promote technology transfer; Shown how Rock and fluid properties are systematic and can be predicted; Shown Correct values must be used to properly calibrate deep-water seismic data; Quantified and examined the influence of deep water geometries in outcrop; Compared and evaluated hydrocarbon indicators for fluid sensitivity; Identified and documented inappropriate processing procedures; Developed inversion techniques to better distinguish hydrocarbons; Developed new processing work flows for frequency-dependent anomalies; and Evaluated and applied the effects of attenuation as an indicator. We have demonstrated that with careful calibration, direct hydrocarbon indicators can better distinguish between uneconomic ''Fizz'' gas and economic hydrocarbon reservoirs. Some of this progress comes from better characterization of fluid and rock properties. Other aspects include alternative techniques to invert surface seismic data for fluid types and saturations. We have also developed improved work flows for accurately measuring frequency dependent changes in seismic data that are predicted by seismic models, procedures that will help to more reliably identify anomalies associated with hydrocarbons. We have been prolific in publishing expanded abstracts and presenting results, particularly at the SEG. This year, we had eight such papers to promote technology transfer. Also, we have begun incorporating outcrop descriptive models in seismic forward models. Our goal for the remaining project period combine the various findings about the deepwater data, present these findings ...
Date: January 30, 2006
Creator: Batzle, Michael; Han, D-h; Gibson, R. & James, Huw
Partner: UNT Libraries Government Documents Department