Petroleum Engineering Laboratory Report

Abstract

This lab report discusses the importance of bulk rock volume in determining the quantity of hydrocarbons in a reservoir. The bulk rock volume is a critical parameter for assessing the commercial viability of a prospect. We utilized a planimeter to measure the area of contours on an isopach map and applied both Simpson's Rule and the Trapezoidal Rule to calculate the bulk rock volume of the reservoir. Our calculations showed that the bulk rock volume plays a significant role in petroleum engineering and reservoir assessment.

Introduction

One of the crucial tasks in petroleum engineering is estimating the quantity of hydrocarbons present in a potential reservoir. This estimation is vital for evaluating the economic feasibility of a prospect. Key physical properties that are of concern include porosity, permeability, net-to-gross ratio, and bulk rock volume. These properties provide essential information for calculating the original oil in place (OOIP) and initial gas in place (IGIP), which are critical factors in determining the commercial viability of an exploration opportunity.

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This lab report focuses on bulk rock volume and its significance in estimating hydrocarbon reserves in a reservoir. We employed a tool known as a planimeter to measure the areas of contours on an isopach map. To calculate the bulk rock volume, we applied both Simpson's Rule and the Trapezoidal Rule, which are mathematical methods for approximating integrals.

Objective

The main objective of this lab experiment is to examine the particle size distribution of a given sediment using a sieve shaker.

Theory

Petroleum reservoirs are capable of containing valuable hydrocarbons in the tiny pores within geological formations.

A reservoir engineer's primary responsibility is to assess the volume of hydrocarbons in a reservoir, which involves determining the Oil Initially In Place (OIIP) and Gas Initially In Place (GIIP). The concept of bulk rock volume plays a crucial role in this assessment.

Bulk rock volume represents the gross rock volume above any hydrocarbon-water contact within the reservoir. It can be determined by mapping and correlating contour maps of the area under consideration. The net-to-gross ratio is then calculated to determine the proportion of the area containing reservoir rocks. The product of bulk rock volume and the net-to-gross ratio yields the net rock volume of the reservoir.

Subsequently, the net rock volume is multiplied by porosity to obtain the total hydrocarbon pore volume. The summation of these volumes provides the estimates for OIIP and GIIP for a given exploration prospect, enabling explorers and commercial analysts to assess its economic viability.

The volumetric method, using a planimeter, is a commonly employed technique for such calculations. A planimeter is a drafting instrument designed to measure the area of a two-dimensional region with an irregular shape. It operates by tracing the perimeter of the region using a mechanically coupled pointer. The area enclosed by the traced path is then calculated.

Planimeters are versatile instruments used in various fields, including petroleum engineering. They are primarily employed to determine the bulk rock volume of potential reservoirs, helping assess whether they contain commercially viable quantities of hydrocarbons.

The bulk rock volume can be calculated using two methods: the Trapezoidal Rule and Simpson's Rule. These rules involve approximating the integral of the contour map using a series of straight lines (Trapezoidal Rule) or parabolic segments (Simpson's Rule). The resulting values are typically measured in acre-feet (acft).

Procedure

Refer to the appendix for the detailed procedure.

Results

Calculations

The following calculations were performed:

Additional data:

• Tmax = 7 ft
• h = 10 ft

Using the Trapezoidal Rule, the bulk rock volume was calculated to be 5.24 x 10^-5 acft.

Using Simpson's Rule, the bulk rock volume was calculated to be 5.26 x 10^-5 acft.

Discussion

The data collected was used to calculate the bulk rock volume using both the Trapezoidal Rule and Simpson's Rule. The volume of each layer was determined by averaging the areas of the top and bottom layers and multiplying the result by the layer thickness on the isopach map.

It is important to note that isopach maps typically show smaller contour areas as the thickness increases. Consequently, these rules, while accurate, tend to slightly overestimate the reservoir volume.

The difference between the results obtained from the two calculation methods was approximately 0.02 x 10^-5 acft. While this difference may appear minor, it can have significant implications in a practical reservoir engineering context, potentially affecting forecasting accuracy.

One contributing factor to this difference is the use of an odd number of intervals (3) in this fractured reservoir. Simpson's Rule generally requires an even number of intervals for increased accuracy.

Another source of error is the reliance on freehand movement when using the planimeter over contours. Even slight jerking movements can impact the accuracy of the readings.

Ultimately, the determination of bulk rock volume is a critical step in assessing the potential of a reservoir to hold commercially viable hydrocarbon quantities. It plays a crucial role in the planning and decision-making processes for petroleum engineering projects.

Conclusion

This laboratory experiment focused on the measurement of bulk rock volume in a reservoir structure using a planimeter. The calculations yielded a bulk rock volume of approximately 5.24 x 10^-5 acft using the Trapezoidal Rule and 5.26 x 10^-5 acft using Simpson's Rule. Bulk rock volume is a key parameter in petroleum engineering, as it influences assessments of reservoir viability and hydrocarbon reserves.

Recommendations

For future experiments and practical applications, it is essential to consider the potential impact of calculation method discrepancies, especially when dealing with odd intervals. Additionally, efforts should be made to minimize errors associated with planimeter use by ensuring smoother and more controlled movements. These recommendations can contribute to more accurate assessments of reservoirs and better-informed decisions in petroleum engineering projects.