Evaluating Oil Reservoir Capacity: A Comparative Analysis of Planimeter and ImageJ Methodologies

Abstract

This study aimed to evaluate the capacity of an oil reservoir using a map displaying contour lines, thereby estimating the volume of the reservoir. The reservoir's area was derived from the map, specifically an Isopach map, where each contour line signifies the depth of the reservoir. Two distinct methodologies were employed for this experiment: the use of a planimeter, a device designed to measure the area of a two-dimensional shape, and ImageJ, a software tool for scaling and analyzing images to obtain accurate measurements.

The findings revealed that reservoirs with greater depths correspond to larger areas and volumes, suggesting that larger reservoirs with substantial volumes are likely to contain significant amounts of hydrocarbons.

Introduction

In the realm of petroleum engineering, discovering an oil reservoir is just the beginning. The engineer's next step is to construct a detailed representation of the reservoir's accumulation. This is where the Isopach map becomes a critical tool. An Isopach map, displaying variations in thickness within a sedimentary layer, enables the calculation of a reservoir's volume or capacity using either a planimeter or ImageJ.

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Isopach maps, characterized by contour lines that represent areas of equal thickness, are invaluable in various geological applications, including hydrographic surveys, stratigraphy, and petroleum geology.

The planimeter serves to measure the area depicted on the Isopach map, while ImageJ, an image processing program, allows for the analysis of area and pixel values, capable of performing measurements of distances and angles, and facilitating image enhancements. Volumetric estimation, or the "geological approach," relies on a comprehensive understanding of the reservoir's geological setting, including its depositional environment, structural complexities, and fluid interactions, to estimate the volume of hydrocarbon-bearing rocks.

An Isopach map illustrates the real stratigraphic thickness variations of a formation or group of formations. The creation of such maps is based on data derived from well cuttings, cores, or geophysical logs, with the maps' contour lines reflecting equivalent stratigraphic thicknesses. These maps not only guide the estimation of drilling depths and the identification of buried structures but also play a pivotal role in calculating oil volumes and determining reservoir capacities.

Objective

The primary aim of this experiment was to ascertain the capacity of an oil reservoir by analyzing an Isopach map, which illustrates the reservoir's area through contour lines.

Theory

The theory underpinning this study involves projecting the geometry of a reservoir onto an Isopach map, comprised of contour lines indicating variations in thickness. This enables petroleum engineers to estimate the reservoir's volume and, consequently, the quantity of hydrocarbons it may contain. Isopach and isochore maps are instrumental in several key aspects, including determining drilling depths, locating buried structures, calculating oil volumes, and estimating elevations below known stratigraphic levels.

The methodologies of Planimeter and ImageJ are employed to ascertain the reservoir's volume from the Isopach map. The Planimeter is used to estimate average thickness within the mapped area, while ImageJ facilitates the digitization and geostatistical analysis of the map. This study also explores volume calculation techniques, such as the Trapezoid and Pyramid Rules, which define the geometry of the reservoir's layers and estimate volumes based on layer thickness and area.

Apparatus

• ImageJ software

Procedure

The procedure involved segmenting the contour into individual lines for analysis in ImageJ, adjusting the scale, and setting the image to an appropriate resolution. The area for each contour was measured and converted into a suitable unit for analysis.

Results

The experiment yielded various measurements of depth, area, and volume, highlighting a direct correlation between the depth of the reservoir and both its area and volume. This relationship indicates that deeper reservoirs tend to have larger areas and volumes, which is consistent with the expectation that larger reservoirs contain more hydrocarbons.

Sample Calculation

The calculation involved converting the measured area from kilometers squared to feet squared, using a conversion factor where 1 km^2 equals 10,763,910.4167 ft^2. The volume was then determined by multiplying the area in feet squared by the depth in feet.

Graphical Analysis

Two graphs were plotted: Depth vs. Area and Depth vs. Volume. These graphs visually represent the relationship between the depth of the reservoir and its corresponding area and volume, further illustrating the trend that as depth increases, so do the area and volume of the reservoir.

Conclusion

This study successfully determined the capacity of oil reservoirs using Isopach maps, revealing a direct correlation between reservoir depth and both area and volume. The use of ImageJ software facilitated accurate area measurements, which, when converted and analyzed, provided valuable insights into the reservoir's characteristics. The findings underscore the importance of depth in evaluating reservoir size and capacity, with deeper reservoirs typically encompassing larger areas and volumes. This correlation is vital for understanding reservoir dynamics and optimizing hydrocarbon extraction strategies, ultimately contributing to more efficient and effective petroleum engineering practices.