Q913 re1 w1 lec 2

1,252 views

Published on

Published in: Education, Business, Technology
0 Comments
5 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
1,252
On SlideShare
0
From Embeds
0
Number of Embeds
6
Actions
Shares
0
Downloads
309
Comments
0
Likes
5
Embeds 0
No embeds

No notes for slide

Q913 re1 w1 lec 2

  1. 1. Reservoir Engineering 1 Course (1st Ed.)
  2. 2. 1. Petroleum Engineering & Its Importance 2. Petroleum Formation 3. Petroleum Extraction A. Drilling B. Production 4. Consumption of Oil 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 2
  3. 3. 1. Reservoir Fluid Behaviors 2. Petroleum Reservoirs A. Oil B. Gas 3. Gas Behavior 4. Gas Properties: Z Factor 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 3
  4. 4. Multiphase Behavior Naturally occurring hydrocarbon systems found in petroleum reservoirs are mixtures of organic compounds that exhibit multiphase behavior over wide ranges of pressures and temperatures. These hydrocarbon accumulations may occur in the gaseous state, the liquid state, the solid state, or in various combinations of gas, liquid, and solid. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 5
  5. 5. Petroleum Engineers Task These differences in phase behavior, coupled with the physical properties of reservoir rock that determine the relative ease with which gas and liquid are transmitted or retained, result in many diverse types of hydrocarbon reservoirs with complex behaviors. Frequently, petroleum engineers have the task to study the behavior and characteristics of a petroleum reservoir and to determine the course of future development and production that would maximize the profit. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 6
  6. 6. Classification of Reservoirs and Reservoir Fluids Petroleum reservoirs are broadly classified as oil or gas reservoirs. These broad classifications are further subdivided depending on: The composition of the reservoir hydrocarbon mixture Initial reservoir pressure and temperature Pressure and temperature of the surface production The conditions under which these phases exist are a matter of considerable practical importance. The experimental or the mathematical determinations of these conditions are conveniently expressed in different types of diagrams commonly called phase diagrams. One such diagram is called the pressuretemperature diagram. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 7
  7. 7. Typical P-T Diagram for a Multicomponent System 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 8
  8. 8. Pressure-Temperature Diagram Although a different hydrocarbon system would have a different phase diagram, the general configuration is similar. These multicomponent pressure-temperature diagrams are essentially used to: Classify reservoirs Classify the naturally occurring hydrocarbon systems Describe the phase behavior of the reservoir fluid To fully understand the significance of the pressuretemperature diagrams, it is necessary to identify and define the following key points on these diagrams: Cricondentherm (Tct), Cricondenbar (pcb), Critical point, Phase envelope (two-phase region), Quality lines, Bubblepoint curve, Dew-point curve 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 9
  9. 9. Oil Reservoirs Depending upon initial reservoir pressure pi, oil reservoirs can be subclassified into the following categories: Undersaturated oil reservoir. If the initial reservoir pressure pi, is greater than the bubble-point pressure Pb of the reservoir fluid Saturated oil reservoir. When pi is equal to the bubblepoint pressure of the reservoir fluid Gas-cap reservoir or two-phase reservoir. If pi is below the bubble point pressure of the reservoir fluid The appropriate quality line gives the ratio of the gas-cap volume to reservoir oil volume. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 11
  10. 10. Crude Oils Crude oils cover a wide range in physical properties and chemical compositions, and it is often important to be able to group them into broad categories of related oils. In general, crude oils are commonly classified into the following types: Ordinary black oil Low-shrinkage crude oil High-shrinkage (volatile) crude oil Near-critical crude oil The above classifications are essentially based upon the properties exhibited by the crude oil, including physical properties, composition, gas-oil ratio, appearance, and pressure-temperature phase diagrams. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 12
  11. 11. Ordinary Black Oil A typical p-T diagram for an ordinary black Liquid-shrinkage curve for black oil oil 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 13
  12. 12. Low-Shrinkage Oil A typical phase diagram for a low-shrinkage Oil-shrinkage curve for low-shrinkage oil oil 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 14
  13. 13. Volatile Crude Oil A typical p-T diagram for a volatile crude oil 2013 H. AlamiNia A typical liquid-shrinkage curve for a volatile Reservoir Engineering 1 Course: (Lec2) Petroleum crude oil Reservoirs 15
  14. 14. Near-Critical Crude Oil A schematic phase diagram for the nearA typical liquid-shrinkage curve for the nearcritical crude 2013 H. AlamiNia critical crude oil Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs oil 16
  15. 15. Liquid Shrinkage for Crude Oil Systems 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 17
  16. 16. Gas Reservoirs In general, if the reservoir temperature is above the critical temperature of the hydrocarbon system, the reservoir is classified as a natural gas reservoir. On the basis of their phase diagrams and the prevailing reservoir conditions, natural gases can be classified into four categories: Retrograde gas-condensate Near-critical gas-condensate Wet gas Dry gas 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 19
  17. 17. Retrograde Gas-Condensate A typical phase diagram of a retrograde A typical liquid dropout curve (liquid system shrinkage volume curve 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs for a condensate20 system)
  18. 18. Near-Critical Gas-Condensate A typical phase diagram for a near-critical Liquid-shrinkage curve for a near-critical gasgas condensate system 2013 H. AlamiNia condensate reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs Reservoir 21
  19. 19. Wet Gas Phase diagram for a wet gas 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 22
  20. 20. Dry Gas Phase diagram for a dry gas 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 23
  21. 21. Compositions of Various Reservoir Fluid Types 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 24
  22. 22. Reservoir Fluid Properties To understand and predict the volumetric behavior of oil and gas reservoirs as a function of pressure, knowledge of the physical properties of reservoir fluids must be gained. These fluid properties are usually determined by laboratory experiments performed on samples of actual reservoir fluids. In the absence of experimentally measured properties, it is necessary for the petroleum engineer to determine the properties from empirically derived correlations. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 27
  23. 23. Natural Gas Constituents A gas is defined as a homogeneous fluid of low viscosity and density that has no definite volume but expands to completely fill the vessel in which it is placed. Generally, the natural gas is a mixture of hydrocarbon and nonhydrocarbon gases. The hydrocarbon gases that are normally found in a natural gas are methanes, ethanes, propanes, butanes, pentanes, and small amounts of hexanes and heavier. The nonhydrocarbon gases (i.e., impurities) include carbon dioxide, hydrogen sulfide, and nitrogen. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 28
  24. 24. Properties of Natural Gases Knowledge of PVT relationships and other physical and chemical properties of gases is essential for solving problems in natural gas reservoir engineering. These properties include:  Apparent molecular weight, Ma  Specific gravity, γg  Compressibility factor, z  Density, ρg  Specific volume, v  Isothermal gas compressibility coefficient, cg  Gas formation volume factor, Bg  Gas expansion factor, Eg  Viscosity, μg The above gas properties may be obtained from direct laboratory measurements or by prediction from generalized mathematical expressions. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 29
  25. 25. Behavior of Ideal Gases The gas density at any P and T: Specific Volume Apparent Molecular Weight Specific Gravity Standard Volume 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 30
  26. 26. Ideal Gases vs. Real Gases In dealing with gases at a very low pressure, the ideal gas relationship is a convenient and generally satisfactory tool. At higher pressures, the use of the ideal gas equation-of-state may lead to errors as great as 500%, as compared to errors of 2–3% at atmospheric pressure. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 31
  27. 27. Behavior of Real Gases Basically, the magnitude of deviations of real gases from the conditions of the ideal gas law increases with increasing pressure and temperature and varies widely with the composition of the gas. The reason for this is that the perfect gas law was derived under the assumption that the volume of molecules is insignificant and that no molecular attraction or repulsion exists between them. Numerous equations-of-state have been developed in the attempt to correlate the pressure-volume-temperature variables for real gases with experimental data. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 32
  28. 28. Gas Compressibility Factor Definition In order to express a more exact relationship between the variables p, V, and T, a correction factor called the gas compressibility factor, gas deviation factor, or simply the z-factor, must be introduced to account for the departure of gases from ideality. The equation has the form of pV = znRT Where the gas compressibility factor z is a dimensionless quantity and is defined as the ratio of the actual volume of n-moles of gas at T and p to the ideal volume of the same number of moles at the same T and p: 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 34
  29. 29. Pseudo-Reduced Properties Calculation Studies of the gas compressibility factors for natural gases of various compositions have shown that compressibility factors can be generalized with sufficient accuracies for most engineering purposes when they are expressed in terms of the following two dimensionless properties: Pseudo-reduced pressure and Pseudo-reduced temperature These dimensionless terms are defined by the following expressions:  2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 35
  30. 30. Standing and Katz Compressibility Factors Chart 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 36
  31. 31. Pseudo-Critical Properties Calculation In cases where the composition of a natural gas is not available, the pseudo-critical properties, i.e., Ppc and Tpc, can be predicted solely from the specific gravity of the gas. Standing (1977) expressed this graphical correlation in the following mathematical forms: Case 1: Natural Gas Systems Case 2: Gas-Condensate Systems 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 37
  32. 32. Pseudo-Critical Properties of Natural Gases Brown et al. (1948) presented a graphical method for a convenient approximation of the pseudo-critical pressure and pseudo-critical temperature of gases when only the specific gravity of the gas is available. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 38
  33. 33. Nonhydrocarbon Components of Natural Gases Natural gases frequently contain materials other than hydrocarbon components, such as nitrogen, carbon dioxide, and hydrogen sulfide. Hydrocarbon gases are classified as sweet or sour depending on the hydrogen sulfide content. Both sweet and sour gases may contain nitrogen, carbon dioxide, or both. A hydrocarbon gas is termed a sour gas if it contains one grain of H2S per 100 cubic feet. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 39
  34. 34. Effect of Nonhydrocarbon Components on the Z-Factor The common occurrence of small percentages of nitrogen and carbon dioxide is, in part, considered in the correlations previously cited. Concentrations of up to 5 percent of these nonhydrocarbon components will not seriously affect accuracy. Errors in compressibility factor calculations as large as 10 percent may occur in higher concentrations of nonhydrocarbon components in gas mixtures. 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 40
  35. 35. Nonhydrocarbon Adjustment Methods There are two methods that were developed to adjust the pseudo-critical properties of the gases to account for the presence of the nonhydrocarbon components. These two methods are the: Wichert-Aziz correction method Carr-Kobayashi-Burrows correction method 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 41
  36. 36. Direct Calculation of Compressibility Factors After four decades of existence, the Standing-Katz z-factor chart is still widely used as a practical source of natural gas compressibility factors. As a result, there has been an apparent need for a simple mathematical description of that chart. Several empirical correlations for calculating z-factors have been developed over the years including: Hall-Yarborough Dranchuk-Abu-Kassem Dranchuk-Purvis-Robinson 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 42
  37. 37. 1. Ahmed, T. (2006). Reservoir engineering handbook (Gulf Professional Publishing). Ch1,2 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 43
  38. 38. 1. Gas Properties: A. Isothermal gas compressibility (Cg) B. Gas formation volume factor (Bg) 2. Crude Oil Properties: A. B. C. D. E. Density Solution gas Bubble-point pressure Oil formation volume factor (Bo) Total formation volume factor (Bt) 2013 H. AlamiNia Reservoir Engineering 1 Course: (Lec2) Petroleum Reservoirs 44

×