One way to understand how well the site can be obtained by considering the fraction of the reservoir that is being sampled by different techniques. For example, suppose you want to find the size of the area sampled from a well that has a radius of 6 inches. Assuming a circular area, the area can be estimated as π r 2 where r is the radius sampled. The area sample is then is 0.7854 ft2. If normalizes the sampled area with the area of \u200b\u200bthe site, say a modest 5 acres, What fraction of the area is directly sampled by the well?. The drainage area is 218,600 ft2 . The fraction of area sampled is 3.59 parts per million which is tiny compared the area of \u200b\u200binterest.
A sign of electrical recording expands the area being sampled. Suppose a training record can penetrate 5 feet from the well, which is reasonable. The fraction of the area being sampled is 4 parts in 10000. The sample size within the drainage area (5 acres) is still a fraction of a percent.
cores and electric logs are a very limited view of the reservoir. A seismic section expands the fraction of area sampled, but the interpretation of seismic data is less precise. The credibility of the seismic data can be better correlated with analysis of hearts or electric profiles.
Fig 1.1Escalas reservoir
Figure 1.1 shows the definition of reservoir scale. Note that these are not universally accepted, but they illustrate the relative scale associated with the property of field measurement. Giga Scale includes information associated with geophysics, such as architecture of the site.
This characterization also includes theories regional plate tectonics, seismic and satellite data. Mega scale reservoir characterization includes well logs, pressure analysis of background and analysis of 3D seismic. Macro scale focuses on information obtained from analysis of cores and fluid properties. The scale involves Micro-level data obtained from pore-scale thin sections and measures of grain size distribution. Each of these scales contributes to the final model reservoir.
From: Fundamentals of Reservoir Engineering - Freddy H. Escobar, Ph.D.
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