sep91


Introduction (ps.gz 17K) , pdf, (src 3K)

intro Seismic monitoring of fluid flow I believe one of the next major breakthroughs in Geophysics will be seismic time-lapse monitoring of subsurface fluid flow . Seismic time-lapse monitoring consists of recording multiple seismic surveys at a single site, repeated over time intervals in which interesting subsurface fluid movement can take place. Integrated with fluid-flow simulation, geology, rock physics and geophysics, spatial estimates of fluid-flow paths, permeabilities and phase-front movement in the subsurface may be inferred from the time-lapse seismic monitor data. Seismic monitoring offers us the exciting possibility of being able to estimate where and how fluids are flowing in the Earth, and may help us assess the role of fluids in crustal processes. Why is monitoring of fluid-flow important? Seismic monitoring of subsurface fluid flow has immense potential for impact in: enhanced recovery of natural energy resources, groundwater and environmental studies, global climate issues, and an improved understanding of plate tectonic mechanisms. ...

Seismic monitoring theory (ps.gz 261K) , pdf, (src 918K)

theory Overview In this chapter, I develop the mathematical relationships between fluid flow, rock physics and reflection seismology. The theory discussed here shows how to perform a complete run of the forward problem: simulate fluid flow, transform the fluid-flow results and a geologic description to saturated rock properties, and predict the resulting seismic reflection data. Similarly, I discuss the theory needed to perform the inverse problem: given seismic reflection data as input, make estimates of the short wavelength elastic impedance structure and long wavelength velocity structure, and infer fluid-flow properties in the subsurface from time-lapse seismic data sets. Introduction Fluid flow plays many important roles in the Earth's crust, including: a resource of potable groundwater, a lubricant along earthquake ...

Feasibility of seismic monitoring (ps.gz 997K) , pdf, (src 4452K)

feas Overview In this chapter, I present a methodology for performing a feasibility analysis to predict the likelihood of seismically detecting and monitoring changes in subsurface rock properties due to fluid flow. Given a geologic description of the subsurface, fluid-flow simulations are performed to predict the spatial distribution of flow pressure, temperature and fluid saturations. These fluid-flow parameters are mapped with rock physics transformations to seismic velocity and density models of the subsurface as a function of the flow simulation and geologic description. After upscaling to seismic wavelengths, seismic reflection data are then simulated and analyzed with realistic noise levels, acquisition parameters and survey errors, to determine if the predicted fluid flow can be detected and monitored with realistic seismic time-lapse data. A detailed feasibility analysis is presented for a case study in the Troll Field, offshore Norway, in which the goal is to determine whether ...

Processing seismic monitor data (ps.gz 1960K) , pdf, (src 157898K)

proc Overview In this chapter, I discuss a seismic data processing strategy to obtain high-resolution subsurface images which are consistent from time-lapse survey to survey. Processing issues will be illustrated with a field data example from the Duri Field, Indonesia, in which six 3-D surveys have been recorded at a shallow steam injection site over a total period of 20 months. I describe the data acquisition geometry and parameters, and the preprocessing steps I used to enhance weak reflection energy in the data. Finally, I discuss my approach to optimizing coherent signal in the NMO stack, migration, and difference sections, and suggest future work to further improve seismic images of the steamflood process. Chapter 5 gives an interpretation of the Duri seismic data integrated with fluid flow, rock physics, seismic modeling and velocity analysis. Introduction The most important feature of time-lapse seismic monitoring data ...

Interpreting seismic monitor data (ps.gz 687K) , pdf, (src 12485K)

interp Overview In this chapter, I present an integrated interpretation of six time-lapse 3-D data sets recorded over a steamflood site in the heavy-oil Duri Field, Sumatra, Indonesia. Migrated images and velocity analysis illuminate fluid-flow features of the steamflood in time-lapse mode. The steam front is visible seismically as large reflection and diffraction responses, and velocity decreases of up to 40 , in a disk centered at the steam injection well. The steam front intensifies in place at a radius of less than 50 m for the first nine months of injection, and then breaks out and rapidly propagates to the northwest of the injection pattern at and beyond the 13-month survey. The steam movement mapped by time-lapse seismic correlates with two temperature observation wells and oil production data from the surrounding producing wells. A thin annulus of hot water (steam condensate) is visible in time slices as a 10 increase in velocity. ...

Conclusion (ps.gz 9K) , pdf, (src 1K)

conc Seismic time-lapse monitoring of subsurface fluid-flow Fluid flow plays many important roles in the Earth's crust, including: a resource of potable groundwater, a lubricant along earthquake fault surfaces, an exchange system with atmospheric fluids, and an association with natural energy resources such as geotherms, mineral deposits, and hydrocarbon reserves. To learn more about the role of fluids in crustal processes, remote sensing of fluid distribution and movement with time-lapse seismic monitoring data may prove to be an extremely useful technique. However, a good understanding of seismic time-lapse monitoring requires an integrated view of three traditionally separate disciplines: fluid flow, rock physics, and reflection seismology. Main contributions of this thesis In this thesis, I have explicitly developed the link between fluid flow, rock physics and seismic wave propagation. This was achieved in four main parts: mathematical aspects of seismic monitoring theory, feasibility analysis of monitoring fluid flow at a given site, ...


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