Glossary of Technical Terms Used in Reservoir Engineering: Original Gas in Place

Original Gas in Place

Understanding Original Gas in Place: A Crucial Metric in Oil & Gas Exploration

In the world of oil and gas exploration, accurately estimating the volume of hydrocarbons present within a reservoir is paramount. One key term used to describe this volume is Original Gas in Place (OGIP), also sometimes referred to as OGP.

OGIP represents the total volume of natural gas originally present within a reservoir at standard conditions (typically 15°C and 1 atm). This figure encompasses all the gas, whether or not it is currently recoverable using existing technology.

Here's a breakdown of what OGIP means:

  • Original: Emphasizes that this is the volume of gas present at the time of reservoir formation.
  • Gas: Refers to the hydrocarbon component of interest, in this case, natural gas.
  • In Place: Indicates that this volume is contained within the reservoir, regardless of recoverability.

Why is OGIP Important?

  • Reservoir Characterization: OGIP provides a fundamental understanding of the reservoir's initial resource potential.
  • Production Planning: Estimating recoverable reserves (the portion of OGIP that can be extracted) is crucial for developing production strategies and planning infrastructure.
  • Economic Viability: OGIP contributes to evaluating the economic feasibility of a project by providing a baseline for potential profits.

Estimating OGIP:

Determining OGIP involves a multi-step process that combines geological and engineering expertise:

  1. Reservoir Characterization: Geologists analyze seismic data, core samples, and well logs to determine the reservoir's volume, porosity (amount of pore space), and gas saturation (proportion of pore space filled with gas).
  2. Gas Composition: The chemical composition of the gas is analyzed to determine its specific gravity and compressibility.
  3. Pressure and Temperature: Reservoir pressure and temperature data are crucial for calculating gas volume at standard conditions.
  4. Material Balance Equation: A complex mathematical model is used to relate the volume of gas initially present to the volume of gas produced and the reservoir's pressure depletion.

OGIP vs. Recoverable Reserves:

It's essential to distinguish OGIP from recoverable reserves, which represents the portion of OGIP that can be economically extracted with current technology.

Factors influencing recoverable reserves:

  • Reservoir characteristics: Porosity, permeability, and pressure influence how easily gas flows.
  • Production technology: Advancements in drilling and extraction technologies can increase recoverable reserves.
  • Economic factors: Market price, cost of production, and environmental regulations play a significant role in determining what is economically viable to produce.

Conclusion:

OGIP is a fundamental concept in oil and gas exploration and development. By understanding the total volume of gas originally present within a reservoir, companies can make informed decisions about resource potential, production strategies, and economic feasibility. While OGIP provides a baseline, it's the recoverable reserves, a fraction of the original gas in place, that ultimately determines a project's success.


Test Your Knowledge

Quiz: Understanding Original Gas in Place (OGIP)

Instructions: Choose the best answer for each question.

1. What does OGIP stand for? a) Original Gas In Place b) Oil Gas In Production c) Oil and Gas Industry Partners d) Original Gas Industry Production

Answer

a) Original Gas In Place

2. Which of these is NOT a factor influencing recoverable reserves? a) Reservoir permeability b) Production technology c) The color of the reservoir rock d) Economic factors

Answer

c) The color of the reservoir rock

3. OGIP represents: a) The total volume of gas that can be extracted from a reservoir. b) The amount of gas that is currently being produced. c) The total volume of gas originally present in a reservoir at standard conditions. d) The maximum amount of gas that can be extracted from a reservoir using current technology.

Answer

c) The total volume of gas originally present in a reservoir at standard conditions.

4. Why is OGIP an important concept in oil and gas exploration? a) It helps determine the best location to build a gas station. b) It helps estimate the potential profits from a project. c) It helps determine the best type of gas to extract. d) It helps determine the best time to start drilling.

Answer

b) It helps estimate the potential profits from a project.

5. Which of these is a step involved in estimating OGIP? a) Determining the reservoir's porosity. b) Analyzing the gas's flavor. c) Determining the reservoir's aesthetic appeal. d) Analyzing the gas's ability to conduct electricity.

Answer

a) Determining the reservoir's porosity.

Exercise: OGIP Calculation

Scenario:

You are an exploration geologist working on a new gas field. You have gathered the following information:

  • Reservoir volume: 10 million cubic meters
  • Porosity: 20%
  • Gas Saturation: 75%
  • Gas Specific Gravity: 0.6
  • Reservoir Temperature: 100°C
  • Reservoir Pressure: 300 bar

Task:

Using the information provided, estimate the OGIP of this gas field.

Assumptions:

  • Standard conditions are 15°C and 1 atm.
  • Use the following formula: OGIP = (Reservoir Volume x Porosity x Gas Saturation x Gas Specific Gravity x Reservoir Pressure) / (Standard Pressure x (1 + (Reservoir Temperature - Standard Temperature) x Gas Expansion Coefficient))

Note: You will need to find the gas expansion coefficient for the specific gas. You can research this online or use a reference book.

Exercice Correction

Calculations:

* Convert reservoir pressure to atm: 300 bar * 1 atm / 1.01325 bar = 296.07 atm
* Convert reservoir temperature to Kelvin: 100°C + 273.15 = 373.15 K
* Convert standard temperature to Kelvin: 15°C + 273.15 = 288.15 K
* Assume the gas expansion coefficient is 0.0035/K (This is a typical value for natural gas, but you should always consult specific data for the gas in question).

* OGIP = (10,000,000 m³ x 0.2 x 0.75 x 0.6 x 296.07 atm) / (1 atm x (1 + (373.15 K - 288.15 K) x 0.0035/K)) 
* OGIP ≈ 3,280,000,000 m³ of gas at standard conditions.

**Therefore, the estimated OGIP of this gas field is approximately 3,280,000,000 cubic meters of gas at standard conditions.**


Books

  • "Petroleum Engineering: Principles and Practices" by Tarek Ahmed: A comprehensive textbook covering various aspects of petroleum engineering, including reservoir characterization and production.
  • "Reservoir Engineering Handbook" by John D. Lee: A detailed reference guide for reservoir engineers, offering insights into reservoir simulation, production optimization, and OGIP estimation.
  • "Elements of Petroleum Reservoir Engineering" by R.C. Earlougher Jr.: This classic text explains the principles of reservoir engineering, including the material balance equation and its applications in OGIP calculations.

Articles

  • "Original Gas in Place: Definition, Calculation, and Applications" by John Smith (hypothetical article): Search for articles with this keyword combination in reputable journals like the Journal of Petroleum Technology, SPE Reservoir Evaluation & Engineering, and Petroleum Geoscience.
  • "Estimating Original Gas in Place: A Case Study" by Jane Doe (hypothetical article): Look for case studies that illustrate the application of OGIP estimation techniques in specific reservoir scenarios.

Online Resources

  • SPE (Society of Petroleum Engineers): Their website (https://www.spe.org) features a vast library of technical papers, articles, and presentations related to petroleum engineering, including topics like OGIP.
  • OGJ (Oil & Gas Journal): This industry publication provides articles, news, and analysis on various aspects of oil and gas exploration and production, including OGIP estimation.
  • Schlumberger: This company's website (https://www.slb.com/resources/technical-articles) features a collection of technical articles covering a wide range of petroleum engineering topics, including OGIP and reservoir characterization.

Search Tips

  • Use specific keywords: Combine keywords like "original gas in place", "OGIP", "reservoir characterization", "material balance equation", "gas volume estimation", etc.
  • Include specific reservoir types: Add keywords like "shale gas", "tight gas", "conventional gas", or "unconventional gas" to focus your search on specific reservoir settings.
  • Limit your search to academic resources: Try using the following search operators: "site:.edu" or "site:.org" to find resources from universities, organizations, or professional societies.
Similar Terms
Budgeting & Financial Control
Communication & Reporting
Oil & Gas Processing
Project Planning & Scheduling
Human Resources Management
Safety Training & Awareness
Regulatory Compliance
Oil & Gas Specific Terms
Most Viewed

Comments


No Comments
POST COMMENT
captcha
Back