Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs

Project and Seminar Material for Petroleum Engineering

Project and Seminar Material for Petroleum Engineering


Abstract


Conventional methods used in determining initial gas-in-place and reserves for a dry gas reservoir entails the use of P/z vs cumulative production data. In a normally pressured gas reservoir, the only important production mechanism is the compressibility of the gas. Many reservoir engineering calculations take advantage of this fact to simplify analysis. However, in deep geopressured gas reservoirs, the compressibility of the gas is much smaller and does not totally dominate production performance. Using simplified approaches may lead to serious errors in these cases. In geopressured systems, the compressibility of the rock and water may be just as large as the gas.

Excluding these sources of energy from performance calculations would result in very pessimistic predictions of production versus pressure. Some investigators have postulated that water will be released from shales as the reservoir compacts during depletion. This would result in an internal water drive similar to aquifer influx. Because the reservoir rock is usually highly compressible and under-compacted, the decrease in pore volume during depletion may be very non-linear. Along with the rock compressibility, the absolute permeability may also decrease with declining pressure.

Several material balance models have been proposed to calculate the initial gas-in-place for abnormally-pressured gas reservoir. The present study is concerned with analyzing the different material balance models used to estimate IGIP for abnormally pressured reservoirs, review the bases and assumptions on which these models have been developed, as well as discuss the strength and weakness of every model. In addition, the study comprises comparative analysis of calculations of the IGIP by these material balance models for some reservoir case studies in the Gulf Coast. A sensitivity analysis is also done on some of the input parameters in these material balance models to determine their effect on estimating the original gas-in-place. Moreover, the present investigation reveals that most of the material balance models analyzed in this study are sensitive to the value of the initial reservoir pressure and the early data. Unfortunately, this is the time when reliable estimate for the IGIP is vital for economic decision regarding the development of such gas reservoirs. However, accurate estimation of the IGIP plays an important role in the evaluation, analysis, prediction of future performance, and making economic decision regarding the development of gas reservoirs.


Chapter One


Introduction

Gas reservoirs with abnormally-high pressures have been encountered all over the world. For these reservoirs, a straight line plot of P/z versus Gp for the early production data and extrapolation to zero reservoir pressure projects incorrect initial gas-in-place (IGIP). The P/z plot is based on the assumption that gas compressibility is the “sole” reservoir driving mechanism. In overpressured gas reservoirs however, grain expansion, formation water expansion and water influx from shale or small associated aquifer, in addition to gas expansion contribute significantly to gas production.

In normally pressured reservoirs, the pore volume change with pressure is considered minimal, and thus the pore volume (formation) compressibility retains a very small constant value. However, in an overpressured gas reservoir, the natural compaction is incomplete, as a large portion of the overburden remains supported by high internal pore pressure. As this pressure is released, through fluid production, the pore space may reduce significantly. Thus, under overpressured conditions, cf is relatively large and may have significant variation with pressure. This becomes important to the material-balance equation, as the pore compressibility is a significant energy term in overpressured reservoirs. In normally pressured gas reservoirs, the energy of the formation is usually negligible compared to the energy of the gas.

Overpressures are subsurface fluid pressures that are greater than the pressures expected under normal hydrostatic conditions. Overpressured reservoirs are abundant in sedimentary basins throughout the world. In the United States, abnormally-pressured gas reservoirs are concentrated in the Gulf Coast, Anardako Basin, Delaware Basin and Rocky Mountain Area. In the Middle East, overpressured gas reservoirs are found in Iraq, Iran and Saudi Arabia. These reservoirs commonly produce light oils and gases and require special evaluation techniques. Prior knowledge of the possibility of encountering overpressures at particular subsurface depths is important when exploring for oil and gas. This is because the presence of higher-than-normal pressure increases the complexity and cost of drilling, well-completions and production operations. Additionally, the effect of overpressures on reservoir behavior must be recognized when predicting performance.

Initial reservoir pressure gradients are normally 0.465 psi/ft of depth, which is the hydrostatic gradient of typical brine. In many producing areas, particularly along the Gulf Coast, reservoirs exist with pressure gradients far in excess of this normal. Gradients of almost 1.0 psi/ft of depth have been observed. Any gradient in excess of 0.465 is abnormal, but the effects of abnormal pressure on reservoir engineering calculations are often ignored unless a gradient of 0.65 psi/ft or more exists. A significant amount of gas exists in abnormally-pressured reservoirs. In the offshore Gulf Coast alone, over 300 gas reservoirs have been discovered with initial gradients in excess of 0.65 psi/ft at depths greater than 10,000 ft [Bernard (1985)].


Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs


Project Material Download

3,000 Naira


The complete material will be sent to you in just 2 steps.

Quick & Simple…


Step One Purchase

Make payment of ₦3,000: through USSD Transfer, Bank Mobile App, ATM Transfer, or POS Transfer to:

Access Bank PlcAccount No.: 0811003731
Name: Samphina Academy
Account Type: Current

Or Click Here to pay with Debit Card

FOR CLIENTS OUTSIDE NIGERIA:
Click Here to pay with Debit Card ($15)
GHANA – Make Payment of 60 GHS to MTN MoMo, 0553978005, Douglas Osabutey 

  PAY WITH CRYPTOCURRENCY


Step Two Purchase

Send the following details through Text Message or WhatsApp Messenger | +234-8143831497

  • Payment Details 
  • Email Address 
  • Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs

The complete material will be sent to your email address after receiving your payment information | T & C Apply


  Contact Our Help Desk


You may also like:

⚠️ Need a different topic? Perform a quick search



Get A Complete Business Plan For Any Business In Nigeria

Business Plan for Businesses in Nigeria

  Business Plans in Nigeria


Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs


Disclaimer

This research material “Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs” is for research purposes and should be used as a guide in developing your research project / seminar work. For no reason should you copy word for word (verbatim) as samphina.com.ng will not be liable for any who copied the material.

The aim of providing this material is to reduce the stress of moving from one school library to another all in the name of searching for research materials. This service is legal because, all institutions permit their students to read previous projects, books, articles or papers while developing their own works. According to Austin Kleon “All creative work builds on what came before”.

samphina.com.ng is only providing this material “Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs” as a reference for your research. The paper should be used as a guide or framework for your own paper. The contents of this paper should be able to help you in generating new ideas and thoughts for your own research. Use it as a guidance purpose only.


How to defend your research work


This is a general guide on how to defend your research work:

1. Prepare For Questions:

If you are preparing for questions that may be asked during your defense, then your answers will flow smoothly and effectively. This will prove your knowledge on the subject e.g “Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs“, and strengthening your argument. Ask friends and family, read your work for them to listen to your presentation, and write down questions. You may be lucky the panel will ask you those you have already prepared on.

2. Strong Summary:

Summarizing your chapters will help keep your audience focused because it is easy for a mind to drift, so providing summaries will ensure your panel will follow along, even if they lose focus for a brief moment. Visual aides, such as graphs and power-point presentations can be very helpful. If you are going to use these, make sure you will practice your presentation with them.

3. Be Confident in Your Research Work:

Not knowing your topic “Comparative Analysis Of Reserves Determination Techniques In Overpressured Gas Reservoirs” inside out will cause you to struggle and ultimately fail with your defense. You need to know the subject from every angle to ensure you are fully prepared for any question that may come your way.

4. Conclusion:

Reinforce your findings to conclude your defense. The finale of your presentation should focus on proving the work that has been done. You may need to recap on what has changed and remained unchanged, if is necessary.

5 . Listen:

Before you get defensive or recite a particular answer, make sure you truly understand the question being asked. Being a good listener is an important quality, because providing an inaccurate or off-topic answer will also weaken the validity of your paper.

Samphina Academy

Samphina Academy is an Online Educational Resource Center that is aimed at providing students with quality information and materials to aid them in succeeding in their academic pursuit.