JNTU
JNTU B.Tech III WELL LOGGING Previous Question Paper (May - 2018 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Define uses of Gamma ray API logs.
Answer
Gamma ray logs are primarily used for lithology identification, correlation between wells, and evaluating the shale volume (Vsh) in a formation. They are also essential in cased-hole environments for depth matching and identifying radioactive markers.
Explain the principle and application of SP log.
Answer
The Spontaneous Potential (SP) log records the natural electrical potential difference between a movable electrode in the borehole and a fixed surface electrode. It arises from electrochemical and electrokinetic potentials at the interface between formation water and mud filtrate. It is used to identify permeable beds, determine formation water resistivity (Rw), and delineate shale/sand boundaries.
What do you understand by focused resistivity?
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What will be cementation exponent of the formation (m) when the core analysis for a single zone with water resistivity of 0.2613 ohm-m are as follows?
| Sample | Permeability(md) | Porosity (%) | RO (Ώ-m) |
|---|---|---|---|
| Core | 7.9 | 9.2 | 34.29 |
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Explain the effect of shale and gas on the sonic derived porosity.
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Explain the process of porosity determination by Neutron log.
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What is the difference between ‘logger’s depth’ and ‘driller’s depth’?
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Can the neutron logging be performed in cased hole? Why or why not explain?
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Explain the significance of Sonic- Neutron cross plots.
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Explain the hydrocarbon estimation by logging operation.
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Part B
What do you understand by Synthetic seismograms? Explain.
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What do you understand by Bore hole compensation in sonic logging operation.
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Calculate the formation water saturation, Sw from the following well log data: Resistivity of completely saturated formation 1.8 Ω-m, True resistivity of formation, 25 Ω-m and n = 2.
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How does Shalyness-Factors influences SP log.
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Explain the terms Free point locater and Plug setting.
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Calculate the porosity in percentage of sandstone reservoir (2.65 g/cc), if the bulk density of the formation is 2.40 g/cc and saturating fluid density is 1.35 g/cc.
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Explain the principle of induction log and its application.
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The sonic log travel time in a loosely consolidated formation is 260μs/m. The matrix and fluid travel times are 130 μs/m and 618 μs/m respectively. Calculate the formation porosity using the time average equation.
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Explain the principle of density log along with its advantages.
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How over pressure zone can be detected with sonic log? Explain with the help of a figure.
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Explain the Environmental corrections that are made in the application of density log.
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Gamma-Ray log of a well which has been drilled through a siliciclastic sequence was obtained. Gamma-Ray reading of a clean sand is 20 API units and the shale baseline has a reading of 120 API units. If the Gamma Ray Shale Index of a formation is 0.25, then what is the Gamma Ray reading across this formation?
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Explain image logs in detail.
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Explain cased hole resistivity log in detail.
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Explain the principle of NMR logging.
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What do you understand by Hinge plot.
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Write a short note on hydrogen index.
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What do you understand by side wall coring? Explain in detail.
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Explain the method of determination of elastic constant of rock using any logging operations.
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