Seismic data

Take an example of estimating gross rock volume, based on seismic data and the results of two wells in a structure (Fig. 7.2). The following cross-section has been generated, and a base case GRV has been calculated. 

Seismic surveys are traditionally an exploration and appraisal tool. However, 3-D seismic is now being used more widely as a development tool, i.e. applied for assisting in selecting well locations, and even in identifying remaining oil in a mature field. This was discussed in Section 2.0. Seismic data acquired at the appraisal stage of the field life is therefore likely to find further use during the development period. 

Appraisal activity should be based upon the information required. The first step is therefore to determine what uncertainties appraisal is trying to reduce, and then what information is required to tie down those uncertainties. For example, if fluid contacts are a major source of uncertainty, drilling wells to penetrate the contacts is an appropriate tool seismic data or well testing may not be. Other examples of appraisal tools are ... 

As of this writing, it has not been possible to use the seismic data which defines the volume of the reservoir to also determine the joint stmcture. Extended flow testing is the most direct measure of the efficiency and sustainabiUty of energy recovery from the reservoir. The use of chemical tracers in the circulating fluid can also provide valuable supporting data with regard to the multiplicity of flow paths and the transit time of fluid within the reservoir (37). 

Consumption of natural gas, as of the mid-1990s, was about 2000 x 10 /yr. Using seismic detection equipment, exploration firms search for gas reserves buried deep underground and beneath the sea floor. Advanced computer systems process the seismic data to pinpoint the most likely locations for reserves. These advanced systems have both cut the time required for data analysis, by 80%, and gready improved the success rate for new drill rigs. 

An important part of interpreting surface seismic data is the identification of the oil- and gas-bearing zones on the seismic data. Vertical seismic profile (VSPs) data are often recorded with a source on the surface and with receivers down the well to accomplish this task. In this way, the travel time to the reservoir can be measured along with other information relating the well data to the surface seismic data. 

Another type of technology that has influenced oil and gas exploration is the acquisition of 3-U surface seismic data. This technology produces so much information that modern interpreters have been forced to give up looking at paper sections and use computers just to view their data. The 3-U seismic surveys are very much like a solid section of the earth. An interpreter can sit at a workstation and literally slice through the data viewing the seismic picture of the earth in almost cvci y way possible. Some companies have assembled virtual reality rooms where the... 

Arts R., Eiken O., et al. Monitoring of C02 injected at Sleipner using time-lapsed seismic data. 2004 Energy Conversion and Management 29 1383-1392. 

Kazemeini H., Juhlin C., et al. Application of the continuous wavelet transform on seismic data for mapping of channel deposits and gas detection at the C02SINK site, Ketzin, Germany. 2008 Geophysics Prospect 57 111-123. 

Data reduction is done by a process called inversion. It is not possible to uniquely derive the structure of a body from first principles based on seismic data. Instead, a model of the structure must be assumed and then the predictions of the model are compared to the observations. The model is then adjusted until the predictions match the observations. The more precise the predictions, the better the model can be tested by the observations. Properties that can be investigated by helioseismic inversion include the density, pressure, sound speed, angular velocity, temperature, and composition. 

It should be emphasized that the expression given in the above equation relating the peak particle velocity, charge-weight-per-delay-period, and distance provides typical values only for planning blasting projects in the absence of seismic data. For further detailed information on blasting situations where the above equation is not applicable, the measurement and interpretation of seismic waves, and techniques necessary to reduce blast vibration, the reader is referred to Refs 1,3 4 Effects of Seismic Waves on Structures. 

Seismic Data Processing. Continuing advances in technology, such as fiber optics, have enabled the capabilities of seismic surveys to be markedly increased so that, where required, a 3-dimensional picture of the rocks in the subsurface can be obtained. Advanced processing has also enabled discrete anomalies in seismic data from individual rock horizons to be analyzed. Under certain conditions, the presence of hydrocarbons can be directly detected. This analysis, sometimes referred to as bright spot technology, has been responsible for numerous discoveries in the Gulf of Mexico in recent years. 

The cold seeps at Hydrate Ridge, cause this site to be labeled a sweet spot of high hydrate concentration, relative to others such as the Blake-Bahama Ridge (ODP Leg 164) example that may be more representative of hydrate deposits in the world. Trehu et al. (2004a) estimate 1.5-2 x 108 m3(STP) of methane for the summit deposit, on the basis of the drilling and seismic data, which also define the limits of the deposit. Trehu (Personal Communication, January 8, 2006) indicated that this amount is comparable to a small gas field, not economical unless facilities are already in place. 

Finetti IR, Boccaletti M, Bonini M, Del Ben A, Geletti R, Pipan M, Sani F (2001) Crustal section based on CROP seismic data across the North Tyrrhenian-Northen Apennines-Adriatic Sea. Tectonophysics 43 135-163... 

The Earth s core is thought to be mainly iron, and seismic data indicate that the inner core is solid and the outer core is liquid. The pressure at the center of the Earth is 3.6 x 1011 Pa, and at this pressure, iron melts at 6350 K. From this information, what can you infer about the solid-liquid equilibrium boundary in the iron high-pressure phase diagram (Pressure and temperature both increase toward the Earth s center.)... 

Figure 9.1 Major subdivisions of the Earth (from Liu Bassett, 1986). The figure shows the pressures and depths of the major boundaries deduced from seismic data.

Condition the flow field to be consistent with deterministic information from isolated point or line observations. Points at which values are actually measured should not be treated as random. Such conditioning will allow information from well tests, specific core observations, and seismic data to be entered into the procedure. Also, the flow field in step two must be globally conditioned to make sure the statistics derived therefrom are the same as those desired. 

Khan A. and Mosegaard K. (2002) An inquiry into the lunar interior a nonlinear inversion of the Apollo lunar seismic data. J. Geophys. Res. 107, E63.1-E63.23. 

Ricard Y., Nataf H.-C., and Montagner J.-P. (1996) The three-dimensional seismological model a priori constrained confrontation with seismic data. J. Geophys. Res. 101, 8457-8472. 

Since the discovery of the Earth s core about a century ago, the idea of iron being the dominant component of the core has gained firm supporting evidence from cosmochemical observations, refined seismic data, high-pressure experimentation, and theories of geomagnetism. Strong support for the idea of an iron core comes from the reasonably close match between the seismolo-gically inferred sound velocity and density of the core and the measured experimental values for iron by shock compression (Al tshuler, 1962 Birch, 1964 McQueen and Marsh, 1966 Press, 1968 Jeanloz, 1979 Brown and McQueen, 1986). This idea was further supported by the... 

The shear and compressional acoustic wave velocities for the inner core are the direct output parameters from seismological observations. In order to make a direct comparison between the seismic data and measured physical properties, measurements of the acoustic velocities for iron at core pressures are required. Only very recently has it become possible to measure the elastic constants of s-Fe at high pressures and room temperature (Mao etal., 1999 Lubbers etal., 2000 Fiquet et al., 2001 Anderson et at, 2001). Recent advances in theory and computational methods have also provided new tools for computing the elastic constants of s-Fe at core pressures (Stixrude and Cohen, 1995 Soderhnd et al., 1996 Cohen et al., 1997 Steinle-Neumann and Stixrude, 1999) and core conditions (Laio et al., 2000 Steinle-Neumann et al, 2001 Alfe et al., 2001). There is considerable disagreement on the elastic constants of s-Fe between experimental results and theoretical calculations. The dilferences in the aggregate shear (FJ and compressional (Vp) wave velocities are smaller (Hemley and Mao, 2001 Steinle-Neumann et ai, 2001). Further improvement of theory and experiment is required to resolve the discrepancies. 

This fact is well established by seismic data (P-wave velocity, bulk modulus, and density), geodynamo observations (the need for it to be reasonably good electrical conductor), and cos-mochemical constraints. This then requires that the core, an iron- and nickel-rich reservoir, chemically balances the silicate Earth to make... 

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