1. What is difference between OIIP/Resource and Reserves?

2. What are different types of flow geometries? (Radial, Linear,

hemispherical and spherical) What is the type of flow geometry in case
of channel reservoirs? (Radial around well bore and linear as we go
away from well bore)
3. What is difference between Brown field and Green field?
4. What are basic types of depositional environments? (Fluvial, Marine,
Transitional, Deltaic)
5. When you call field as “Matured Field”?
6. Draw relative permeability curve for oil-wet reservoir?
7. What is difference between Free water level (FWL) and OWC? Are they
same or different?
8. What is the favorable mobility ratio for waterflooding? (M>>>1)
9. If the porosity of two reservoirs are 5% and 20%, which one would have
larger transition zone height and Why?(low porosity reservoir, 5%)
10.If a same reservoir, first case having a gas and second case having oil.
Would both have same height of transition zone or not? Why or why
not?
11.When should we start EOR in the life of the field?
12.If the Swc (irreducible water saturation) is 20%, what is the movable oil
saturation? (less than 80%)
13.For 2 phase reservoir, If relative permeability of water is 0.4 at particular
saturation what will be relative permeability of oil at same saturation?
(“Kro+Krw” never equals to 1) Further, what is the difference between
relative permeability and effective permeability of a phase??
14.According to API classification of reserves what does 1P, 2P and 3P
signifies? What does P1, P2 and P3 stands for?

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15.If porosity of a conventional reservoir is 8% what would be the
approximate value of its perm 1000 mD, 100md, 10mD or 0.1mD?
16.What is the work of reservoir engineer? What are the task it performs?
(What you will be doing as reservoir engineer?)
17.What are the things you can determine from well test analysis?
(Permeability, Skin, Initial Pressure, Presence of Flow boundary i.e.
fracture, channel, closed boundary or parallel sealing faults)
18.What do you mean by miscibility? What is First-Contact Miscibility (FCM)
and Multi-Contact Miscibility (MCM)? (A little bit difficult one)
19.Which drive mechanism would give maximum recovery for gas reservoir
and why? (depletion)
20.Why it is recommended to produce oil from reservoir at pressure just
below the bubble point pressure?
21.What are different types of traps? (Structural, Stratigraphic,
Hydrodynamic)
22.What are the basic components required for hydrocarbon reservoir?
(Source Rock, Reservoir Rock, Cap Rock- Seal)
23.If reservoir fluid has Bo= 1.95, describe the oil? (It’s API range, type of
oil, oil compressibility, etc.) The question you asked when we came for
training.
24.What are the different methods used to determine permeability? (PTA,
Core Analysis)
25.5000 Bbls of oil occupies 4000 Bbl at surface and yields 20,000 SCF of
gas. What is Bo and Rs?
26.If Sp Gr of Oil is 1.0 , what will be its value in API?
27.What is mobility ratio? What do you mean by favourable mobility ratio?

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28.What happens when unfavourable mobility ratio exists between
displacing and displaced phase?
29.Is Recovery factor dependent on mobility ratio? How can we alter
unfavourable mobility ratio to favourable?
30.What is Amott Harvey Wettability Index? How will the performance of
an oil wet reservoir reflect?
31.What is IOR and EOR?
32.What are the means to reduce ROS to waterflood?
33.Classify the petroleum reservoir systems based on the P-T diagram.
34. What is the difference between absolute and effective porosity?
35.What are the factors which plays important role during the primary
production?
36.What is retrograde condensation?What can be done to stop the loss due
to retrograde condensation process in the reservoir?
37.At what pressure the viscosity of oil is minimum and why?
38.If Solution Gas (Rs)or Formation volume Factor (FVF) curve of typical oil
is provided then how will you identify the saturation pressure from the
data. In an under-saturated reservoir initial reservoir pressure should be
more or less than Saturation/Bubble point pressure?
39.Why solution gas is constant above Saturation/Bubble point pressure?
40.What is the difference between oil Formation Volume Factor and
Shrinkage factor?
41.When pressure is lowered, why does oil Formation Volume Factor
increases till bubble point and subsequently decreases?
42.What are the secondary recovery mechanisms and which kind of fluids
are injected? What is the difference between secondary & tertiary
recovery methods?

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 43.In which kind of reservoir, retrograde condensation takes place?
44.Why Gas Deviation Factor (GDF) is used in reservoir engineering
calculations? What is the range of GDF and what is the value of GDF for
ideal gases?
45.What is saturation/bubble point pressure (Pb)?
46.What will be the producing GOR behavior in an under saturated oil
reservoir when reservoir pressure goes below Bubble Point pressure?
And why ? What is the basic use of oil and gas FVF? What is application
of two-phase oil FVF ?

Porosity and Permeability Concepts

1. What are the factors controlling porosity?
(Depth, lithology,grain size distribution)
2. What is the difference between absolute porosity and effective porosity?
3. What is the porosity for cubicle packing of uniform spheres. Which
arrangement of uniform spheres has the most compact packing? (Ans.
47.6 %, Rhombohedral packing : 25.96 %)
4. What is the difference between primary porosity and secondary
porosity?
5. Which kind of grain size distribution is likely to have more porosity, well
sorted uniform size or poorly sorted?
6. What is the difference between rock compressibility and pore
compressibility?
7. Define Darcy’s law. What is 1 Darcy permeability?
8. What is the average permeability of beds in series and beds in parallel?
9. What all factors can affect permeability measurements in laboratory?
10. What is Klinkenberg effect?. How can liquid permeability be estimated
from air permeability?

B. Capillary pressure, Wettability and Relative permeability

18. What is the difference between imbibition and drainage process?

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1. What all factors govern the shape of capillary pressure curve? (Ans. Size
and distribution of pore throats, fluids and solids involved and history of
saturation process)
2. What are the different commonly used methods for measuring capillary
pressure in laboratory? (Ans. Desaturation or displacement process,
Centrifuge method, Dynamic capillary pressure method and mercury
injection method)
3. What is Leverette’s ‘J’ function and what is it used for?
4. What are the different types of wettability that reservoir rocks have?
5. What is the difference between absolute permeability, effective
permeability and relative permeability?
6. Draw and explain different elements of oil-water or gas-oil relative
permeability?
7. What is relative permeability hysteresis?
8. What are factors affecting the shape of relative permeability curve?
(Ans. Pore size distribution, wettability and saturation history)
9. What are the different methods of measuring relative permeability in
laboratory? (Ans. 1. Steady state flow process 2. Unsteady state process
3 capillary pressure method)

C. Fundamentals of behaviour of hydrocarbon fluids

28. Draw and explain the phase diagram of a multi-component hydrocarbon

system.
1. What is retrograde condensation?
2. What is the difference between a wet gas and a retrograde gas
condensate reservoir?
3. What are disadvantages of producing gas condensate field on depletion?
How can these loses be minimised?
4. What is the difference between a high shrinkage and a low shrinkage oil
reservoir? Draw the phase envelope to illustrate the difference?
5. What is gas deviation factor or Z-factor of natural gases?
6. What are pseudo-critical and pseudo-reduced properties for mixtures of
natural gases?

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7. What are the different methods of obtaining representative reservoir
fluid sample?
8. When is re-combination sampling preferred?
9. What are different PVT studies carried out for normal black oil system?
10. What other PVT studies are done for gas-condensate systems?
11. Why is multi-stage separation done?
12. What is the difference between flash liberation and differential
liberation process?
13. What is formation volume factor. Show its relationship with pressure?
14. How does viscosity of undersaturated oil changes with pressure?
15. What are different uses of PVT data in reservoir engineering studies?
16. In absence of laboratory data how can the properties of oil and gas be
estimated? What all basic data is required for PVT correlations?
17. In FVF and pressure relationship, when pressure decreases from initial,
the FVF increases upto bubble point and then subsequently declines
with pressure. Why?

D. Reservoir drive mechanism, MBE and displacement processes

46. What are the different drive mechanisms?
1. Which drive mechanism is most efficient and which is least efficient?
2. What all information can be derived from MB calculations? What basic
data is required for MBE?
3. What are drive indices?
4. How can GIIP be estimated graphically from pressure data of a
volumetric dry gas reservoir?
5. How can you establish whether a gas field is having aquifer support or
not by P/Z vs Gp plot for dry gas reservoir.
6. What are the typical characteristics of solution gas drive reservoir? Why
does produced GOR trend initially decreases, increases subsequently
and again declines?
7. What are the typical characteristics of water drive reservoir?
8. Which kind of reservoirs are rate sensitive? Is depletion type reservoir
rate sensitive ?

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9. What is a fractional flow curve ?
10. What is mobility ratio? How does it affect breakthrough ?
11. What is the shape of fw vs Sw curve for less than unity mobility ratio
displacement process? How does shape of fractional flow curve changes
with mobility ratio?
12. Why recovery of gas is less in a water drive reservoir than in a depletion
drive reservoir?

E. Enhanced Oil Recovery

59. What is EOR? What are the different types of EOR methods being used?
1. What are the basic screening criterions for identifying appropriate EOR
techniques?
2. What is the difference between enhanced oil recovery process and
artificial lift method?
3. What is the difference between a miscible displacement and immiscible
displacement?
4. What is the role of polymer flooding in reservoirs? What advantages it
offers over waterflooding?
5. What is the purpose of Surfactant EOR processes?
6. What is viscous fingering? How can it be minimised?
7. What is the difference between a cyclic steam process (huff-n-puff) and
steam flooding?
8. What is the concept that works behind Polymer flooding process?
9. What is the concept that works behind Thermal processes?
10. What is the concept that works behind Surfactant flooding?
11. Name the fields and EOR methods under application in ONGC?

F. Production Engineering
71. What are the different artificial lift methods commonly used?
12. What is the difference between intermittent gas lift and a continuous
gas lift? In what type of wells these lifts are used?
13. When is Gas lift preferred over SRP?

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14. What is productivity index of a well?
15. What is Vogels IPR? How is it useful?
16. What are reasons for deviation of IPR from linearity at high rates?
17. How can you estimate the optimum production rate of well with a given
tubing size?
18. What are the different correlations available for multi-phase flow
calculations?
19. Why are surface chokes applied?
20. What are the advantages of horizontal wells over vertical wells. Where
are they most suited? What are multi-laterals?

21. What do you mean by gas/water coning. How can it be minimised?

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22. What all information can be obtained from pressure transient tests?
23. What are the causes of formation damage?
24. How can sand production in a well be controlled?
25. What is hydraulic fracturing and when is it done?
26. What is acid fracturing?
27. Two wells of same skin factor (positive), but different permeability say
100 md and 1000 md are identified. Which one will you choose for
stimulation job if you have to do only one stimulation ?
28. What are the reasons for a producing oil/gas well getting ceased?
29. When is artificial lift required in the producing life of a field?
30. What type of artificial lift will you prefer in depletion drive reservoir
particularly when reservoir pressure has declined below saturation
pressure and wells are flowing with high GOR?
31. What are the different flow regimes in a vertical multiphase (liquid &
gas) flow? What factor governs the flow regimes?
32. What is stimulation? What type of stimulation technique one would
prefer in a naturally occurring very low permeability reservoir?
33. What techniques are used for separation of oil & water ?
34. Why is multi bean study carried out ? What Important parameters
determined from these studies ? What is AOFP ?
G. Drilling and Cementation
35. What are the functions of mud?
36. What are the types of casing strings?
37. What is a blow-out? – What are the symptoms of blow-out ?
38. What is mud filtrate ? How does it affect the productivity of the well ?

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39. How can it be avoided? If not, how can it be restored ?
40. Why is casing required in completing a well?
41. Why is cementation carried out? What is primary and secondary
cementation?
42. What type of log is used to find the quality of cementation?
43. What are the types of well profiles while drilling?
44. Why are surface, intermediate and conductor casings used?
45. What are the functions of drilling mud ? What are types of drilling mud ?
46. What is the difference between open hole and cased hole completion?
47. Which are the factors that control penetration rate of bit?
48. What is conventional and sidewall coring?
49. What is DST and what information does it give?
50. Why is Barite (Barium Sulphate) used in drilling fluid
51. What are the producing Assets of ONGC? Which is the largest producing
field of ONGC? What is the annual oil production of ONGC? Name some
producing fields of the various Assets of ONGC.
52. What is NPV, discount factor, IRR, Pay out period?

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