GATE Petroleum Engineering Reservoir Engineering Syllabus

Reservoir Engineering syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Reservoir Engineering in GATE Petroleum Engineering, not a summary of it.

1. 1

   Petrophysical properties of reservoir rocks

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

2. 2

   Coring and core analysis

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

3. 3

   Reservoir fluid properties

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

4. 4

   Phase behaviour of hydrocarbon system

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

5. 5

   Flow of fluids through porous media

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

6. 6

   Water and gas coning

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

7. 7

   Reservoir pressure measurements

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

8. 8

   Reservoir drives, drive mechanics and recovery factors

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

9. 9

   Reserve estimation & techniques

   overview

   Examined as a single unit within Reservoir Engineering — no further topic split in the official outline.

Reservoir Engineering flashcards for GATE Petroleum Engineering

22 of 50 cards from the Reservoir Engineering deck — real questions with worked answers.

1. Define porosity ($\phi$) of a reservoir rock and give its defining equation.

   Porosity is the fraction of the bulk rock volume occupied by pore (void) space: $$\phi = \frac{V_p}{V_b} = \frac{V_b - V_s}{V_b}$$ where $V_p$ is pore volume, $V_b$ bulk volume, and $V_s$ grain (solid) volume. It is usually expressed as a fraction or percentage.

2. Differentiate between total (absolute) porosity and effective porosity.

   Total porosity is the ratio of all pore space (connected + isolated) to bulk volume, whereas effective porosity counts only interconnected pores that contribute to fluid flow. For reservoir flow, effective porosity is the relevant quantity; $\phi_{eff} \leq \phi_{total}$.

3. State Darcy's law for linear, horizontal, single-phase flow and define the terms.

   $$q = -\frac{k A}{\mu}\frac{dP}{dx}$$ where $q$ is volumetric flow rate, $k$ permeability, $A$ cross-sectional area, $\mu$ fluid viscosity, and $\frac{dP}{dx}$ the pressure gradient. The negative sign indicates flow from high to low pressure.

4. What is the SI/practical unit of permeability and how is 1 darcy defined?

   Permeability has units of area ($\text{m}^2$). 1 darcy is the permeability that allows a fluid of $1\ \text{cP}$ viscosity to flow at $1\ \text{cm}^3/\text{s}$ through a $1\ \text{cm}^2$ area under a gradient of $1\ \text{atm/cm}$. Numerically $1\ \text{darcy} \approx 9.869 \times 10^{-13}\ \text{m}^2 \approx 0.987\ \mu\text{m}^2$.

5. Distinguish absolute, effective, and relative permeability.

   Absolute permeability is the rock's permeability to a single saturating fluid. Effective permeability ($k_o, k_w, k_g$) is the permeability to one phase when more than one phase is present. Relative permeability is the ratio of effective to absolute permeability: $$k_{ri} = \frac{k_i}{k}, \quad 0 \leq k_{ri} \leq 1$$

6. Write the radial (steady-state) Darcy flow equation for an oil well and define each variable.

   $$q = \frac{2\pi k h (P_e - P_{wf})}{\mu \ln\!\left(\frac{r_e}{r_w}\right)}$$ where $h$ is net pay thickness, $P_e$ external boundary pressure, $P_{wf}$ flowing bottomhole pressure, $r_e$ drainage radius, and $r_w$ wellbore radius.

7. Define formation volume factor of oil, $B_o$, and give its formula.

   $B_o$ is the volume occupied at reservoir conditions by the oil (plus its dissolved gas) per unit volume of stock-tank oil: $$B_o = \frac{V_{oil\ at\ reservoir\ conditions}}{V_{oil\ at\ standard\ conditions}}$$ Units are $\text{rbbl/STB}$ and $B_o \geq 1$.

8. Define the solution gas-oil ratio $R_s$.

   $R_s$ is the volume of gas (measured at standard conditions) dissolved in one stock-tank barrel of oil at a given reservoir pressure and temperature: $$R_s = \frac{V_{gas\ dissolved,\ sc}}{V_{oil,\ sc}}\quad (\text{scf/STB})$$ It increases with pressure up to the bubble point, then stays constant.

9. What is the bubble point pressure of a reservoir oil?

   The bubble point pressure ($P_b$) is the pressure at a given temperature at which the first bubble of gas comes out of solution from the oil. Above $P_b$ the oil is undersaturated; at and below $P_b$ it is saturated and free gas exists.

10. Write the real gas law / equation of state used for reservoir gases.

    $$PV = znRT$$ where $z$ is the gas compressibility (deviation) factor accounting for non-ideal behavior, $n$ moles, $R$ universal gas constant, and $T$ absolute temperature. For ideal gas $z = 1$.

11. Give the expression for the gas formation volume factor $B_g$.

    $$B_g = \frac{V_{res}}{V_{sc}} = \frac{z T P_{sc}}{T_{sc} P}$$ In field units $B_g = 0.02827\,\frac{zT}{P}$ ($\text{ft}^3/\text{scf}$), with $T$ in $^\circ R$ and $P$ in psia. $B_g$ is much less than 1.

12. Define isothermal compressibility of a fluid and write its equation.

    $$c = -\frac{1}{V}\left(\frac{\partial V}{\partial P}\right)_T = \frac{1}{\rho}\left(\frac{\partial \rho}{\partial P}\right)_T$$ It is the fractional change in volume per unit pressure change at constant temperature. For an ideal gas $c_g = \frac{1}{P}$.

13. State the general (saturated) form of the material balance equation expansion terms qualitatively.

    Reservoir voidage from production is balanced by: expansion of oil + originally dissolved gas, expansion of the gas cap, expansion of connate water and reduction of pore volume, and any water/gas influx or injection. Schematically: production withdrawal = oil/gas expansion + gas-cap expansion + rock-and-water expansion + influx.

14. Write the rock-and-fluid (connate water) expansion compressibility term used in material balance.

    $$c_e = \frac{c_w S_{wc} + c_f}{1 - S_{wc}}$$ where $c_w$ is water compressibility, $c_f$ formation (pore) compressibility, and $S_{wc}$ connate water saturation. This effective compressibility drives undersaturated-reservoir depletion.

15. For a volumetric depletion gas reservoir, what plot is used to estimate $G$ (gas in place) and what is its equation?

    The $\frac{P}{z}$ vs cumulative production $G_p$ plot, which is linear: $$\frac{P}{z} = \frac{P_i}{z_i}\left(1 - \frac{G_p}{G}\right)$$ Extrapolating to $\frac{P}{z}=0$ gives $G$; the x-intercept equals the original gas in place.

16. Give the volumetric equation for original oil in place (OOIP) in stock-tank barrels.

    $$N = \frac{7758\,A\,h\,\phi\,(1 - S_{wc})}{B_{oi}}\ (\text{STB})$$ where $A$ is area (acres), $h$ net pay (ft), $\phi$ porosity, $S_{wc}$ connate water saturation, $B_{oi}$ initial oil FVF, and $7758$ converts acre-ft to bbl.

17. Give the volumetric equation for original gas in place (OGIP).

    $$G = \frac{43560\,A\,h\,\phi\,(1 - S_{wc})}{B_{gi}}\ (\text{scf})$$ with $A$ in acres, $h$ in ft, and $B_{gi}$ the initial gas FVF in $\text{ft}^3/\text{scf}$; $43560$ converts acre-ft to $\text{ft}^3$.

18. List the natural drive mechanisms of an oil reservoir.

    Solution (depletion/dissolved) gas drive, gas-cap drive, water drive (edge or bottom), gravity drainage, and combination (mixed) drive. Each differs in pressure decline behavior, GOR trend, and ultimate recovery.

19. Compare typical recovery factors of solution-gas drive, gas-cap drive, and water drive.

    Solution-gas drive: lowest, about $5$–$30\%$. Gas-cap drive: intermediate, about $20$–$40\%$. Water drive: highest, about $35$–$75\%$ (strong water drive). Recovery improves with mechanisms that maintain pressure.

20. How does producing GOR behave under a solution-gas (depletion) drive?

    GOR first stays near $R_{si}$, then rises sharply to a maximum as free gas becomes mobile and is preferentially produced once pressure drops below the bubble point, and finally declines as the reservoir gas is depleted. Reservoir pressure falls rapidly throughout.

21. Define irreducible (connate) water saturation $S_{wc}$.

    $S_{wc}$ is the lowest water saturation that can be achieved in the rock by displacing water with a non-wetting hydrocarbon phase; this water is held by capillary forces in small pores and as films and is effectively immobile during hydrocarbon production.

22. Define residual oil saturation $S_{or}$.

    $S_{or}$ is the oil saturation remaining and trapped (immobile) in the swept region of the reservoir after a displacement process such as waterflooding; it represents oil that cannot be recovered by that displacement due to capillary trapping.

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