Formation Evaluation and Log Interpretation - Petroleum Formation Evaluation - Petroleum Engineering Previous Year Questions

1

2016 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2016

Using the gamma ray log given in the figure, the shalliness index for point S is ______%.

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2

2016 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2016

A section of a clean sandstone reservoir was logged and found to have a porosity of 10%. The cementation (m) and saturation (n) exponents are equal to 2. The constant 'a' in Archie's saturation equation is 1. The formation water resistivity is 0.036 ohm-meter and the formation resistivity is 10 ohm-meter.
The water saturation in the reservoir is_____%.

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3

2017 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2017

The sonic log travel time in a loosely consolidated formation is 260 μs/m. The matrix and fluid travel times are 130 μs/m and 618 μs/m, respectively. A correction factor of 1.0 may be used in a Wyllie time average equation for simplification. The calculated formation porosity using the Wyllie time average equation is ______%. (write answer with two decimal places)

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4

2018 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2018

A cylindrical sandstone core, 7.5 cm long and 3.5 cm diameter has grain density of 3 g/cm³. If the mass of the dry core is 200 g, the porosity of the core is __________%. (rounded-off to two decimal places)

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5

2018 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2018

Which one of the following options represents the typical sequence of applying cut-offs for pay zone identification in a conventional reservoir?

A

porosity, saturation, shale

B

porosity, permeability, saturation

C

shale, porosity, saturation

D

shale, porosity, permeability

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6

2018 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2018

A dry core was subjected to the mercury injection test in the laboratory. Following are the related details:
Average formation porosity = 0.2
Formation volume factor, B_o = 1.2 reservoir-bbl/STB
Oil API° = 32, Specific gravity of water = 1.1
Hydrostatic gradient = 0.433 psi/ft
(σ_OW cos θ)_res = 26 dyne/cm, where σ_OW is the oil-water interfacial tension and θ is the contact angle
(σ_AM cos θ)_lab = 367 dyne/cm, where σ_AM is air- mercury interfacial tension and θ is the contact angle
Average drainage area = 80 acres
(1 acre-ft = 7758 bbl)
The Table shows the laboratory data for capillary pressure at different mercury saturations.

Pc (psia)	Mercury saturation (SHg)
10	0.0075
17	0.25
30	0.50
108	0.70
2000	0.85

\( P_c = \frac{2\sigma \cos \theta}{r} \) and the average water saturation (S_w) for the productive column is 0.25. The Original Oil in Place (OOIP) in the productive column where S_w ≤ 0.5 is _________ MMSTB. (rounded-off to one decimal place)

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7

2018 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2018

A well is drilled with water based mud. The water saturation in the completely flushed zone (no formation fluid residual) is given by,
\( S_{xo} = \left( \frac{a}{\phi^2} \times \frac{R_{mf}}{R_{xo}} \right)^{1/2} \),
where, R_mf and R_xo are the mud filtrate resistivity and flushed zone resistivity, respectively. Use, a = 1.0 and R_xo = 25 R_mf.
The calculated porosity (φ) of the formation is ______. (in fraction rounded-off to two decimal places)

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8

2020 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2020

Which one of the following options best represents the correct order of increasing thermal conductivity of the subsurface formations?

A

Coal < Shale < Dolomite < Evaporite

B

Evaporite < Shale < Coal < Dolomite

C

Coal < Shale < Evaporite < Dolomite

D

Shale < Coal < Evaporite < Dolomite

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9

2020 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2020

The following primary and secondary porosity types are prevalent in the subsurface formations:
1. Interparticle
2. Intraparticle
3. Fracture
4. Solution
5. Bedding plane voids
6. Channel
Which one of the following options represents the correct combination?

A

Primary (1, 2, 3); Secondary (4, 5, 6)

B

Primary (1, 2, 5); Secondary (3, 4, 6)

C

Primary (1, 3, 6); Secondary (2, 4, 5)

D

Primary (2, 4, 6); Secondary (1, 3, 5)

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10

2020 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2020

Given the following data of a shale gas formation:

W_TOC (weight fraction of total organic carbon (TOC)) = 0.10
S_wT (total water saturation) = 0.25
ρ_TOC (density of TOC) = 1.10 g/cm³
ρ_m (density of matrix) = 2.65 g/cm³
ρ_g (density of gas) = 0.35 g/cm³
ρ_w (density of water) = 1.00 g/cm³
ρ_B (formation bulk density) = 2.00 g/cm³

Consider that only water and gas are present in the formation and the following equations apply,

ρ_B = (ρ_m×(1-φ_T)+ρ_f×φ_T) / (1-W_TOC×(1-ρ_m/ρ_TOC)) , ρ_B = (ρ_TOC×V_TOC/W_TOC) + φ_T × ρ_f

Where, ρ_f is the fluid density, φ_T is the total porosity, and V_TOC is the volume fraction of TOC.

The volume fraction of TOC (rounded off to two decimal places) is ______.

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11

2021 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2021

Match the following rock types (GROUP I) with their respective chemical compositions (GROUP II) from the given options.

GROUP I	GROUP II
(P) Sandstone	(I) A non-clastic carbonate rock consisting mainly of the mineral calcite.
(Q) Limestone	(II) A non-clastic chemical rock composed of mineral halite.
(R) Shale	(III) A siliciclastic rock formed mainly of sand.
(S) Rock salt	(IV) A fissile rock with a laminated structure, formed by consolidation of clay or mud.

A

P – III, Q – II, R – IV, S – I

B

P – II, Q – III, R – I, S – IV

C

P – III, Q – I, R – IV, S – II

D

P – III, Q – I, R – II, S – IV

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12

2022 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2022

The Timur chart for estimating the permeability is the plot between

A

Porosity and Water Saturation

B

True Resistivity and Water Saturation

C

Porosity and Irreducible Water Saturation

D

Porosity and True Resistivity

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13

2022 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2022

Which of the following Logging tool combinations are required to estimate the Hydrocarbon Initial in Place (HCIP)?

A

Resistivity Log, Neutron Log and Gamma Ray Log

B

Sonic Log, Neutron Log and Gamma Ray Log

C

Resistivity Log, Density Log and Gamma Ray Log

D

Neutron Log, Density Log and Sonic Log

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14

2022 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2022

The log data obtained for a particular well section are shown in the following figures. Identify the CORRECT interpretations for different zones.

A

Zone 1 – shale                                    Zone 2 – clean sand with oil
Zone 3 – clean sand with gas                 Zone 4 – clean sand with water

B

Zone 1 – clean sand with gas                    Zone 2 – clean sand with oil
Zone 3 – clean sand with water               Zone 4 – shale

C

Zone 1 – shale                                                      Zone 2 – clean sand with gas
Zone 3 – clean sand with oil                            Zone 4 – clean sand with water

D

Zone 1 – clean sand with water                Zone 2 – clean sand with oil
Zone 3 – clean sand with gas                            Zone 4 – shale

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15

2022 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2022

In a sandstone reservoir, the density log reads 2.11 g/cc and sonic log reads 90 μs/ft. The other parameters are given below:
Matrix density (ρ_ma) = 2.68 g/cc
Fluid density (ρ_fl) = 1.0 g/cc
Compressional wave travel time in matrix (Δt_ma) = 54 μs/ft
Compressional wave travel time in fluid (Δt_fl) = 189 μs/ft
The calculated secondary porosity of the reservoir is ______ % (rounded off to the nearest integer).

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16

2022 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2022

The hydrogen index (HI) of a potential source rock is 500. If 400 g of the same rock produces 6000 mg of hydrocarbons during a thermal pyrolysis at the maximum temperature, the calculated total organic content (TOC) of the rock is __________ weight % (rounded off to one decimal place).

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17

2024 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2024

A core sample from a well-consolidated sand has a length of 10 cm, diameter of 4 cm, and a resistance (r) of 100 Ω at \(T_2 = 200 \ ^\circ F\) when completely saturated with brine. The resistivity \(R_w(T_1)\) of brine is 0.5 Ω·m at \(T_1 = 75 \ ^\circ F\). The cementation factor, m = 2 and the tortuosity factor, a = 1.
Use \(R_w(T_2) = R_w(T_1) \frac{(T_1+6.77)}{(T_2+6.77)}\), where \(T_1\) and \(T_2\) are in °F.
The porosity (in fraction) of the core sample using generalized Humble’s formula at 200 °F is ______ (round off to two decimal places).

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18

2025 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2025

Which of the following logging tool(s) underestimate(s) porosity in a gas-bearing formation?

A

Neutron log

B

Nuclear Magnetic Resonance (NMR) log

C

Sonic log

D

Density log

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19

2025 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2025

The formation resistivity factor (\( F \)) is related to the formation porosity (\( \phi \)) in a water-bearing carbonate formation by the following correlation
\[ F = 0.9\phi^{-2} \]
where \( \phi \) is in fraction. The resistivity of the invaded zone of the formation obtained by the Microspherically Focused Log (MSFL) is 4.5 \( \Omega\cdot m \), and the resistivity of the mud-filtrate is 0.05 \( \Omega\cdot m \).
The formation porosity is ______% (rounded off to one decimal place).

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20

2025 · Petroleum Engineering · Petroleum Formation Evaluation · Formation Evaluation and Log Interpretation

Petroleum Engineering (PE) 2025

The laboratory analysis data obtained from the core is as follows:
Weight of clean dry core in air = 30 g
Weight of core completely saturated with oil = 32 g
Weight of saturated core completely immersed in oil = 24 g
If the density of oil used for saturation of core during the experiment is 0.88 g/cc, then the effective porosity of the core is ______ % (rounded off to two decimal places).

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