SPE - Society of Petroleum Engineers Formation Evaluation and Logging Questions and Answers

Question 1

A well is drilled with fresh mud (Rmf > Rw) into a sequence of formations.
The Spontaneous Potential (SP) log shows a strong negative deflection against a thick, permeable sandstone formation.
What is the most likely interpretation of this response?

Accepted Answer

The formation is likely a clean, permeable sandstone containing saline formation water.

Answer

The formation is a low-permeability shale.

Answer

The formation contains hydrocarbons, causing the negative deflection.

Answer

The mud filtrate and formation water have nearly identical salinities.

Question 2

While analyzing a suite of logs from a carbonate reservoir, you observe a zone where the neutron porosity log reads significantly higher than the density porosity log, both on a limestone matrix scale. The gamma ray log shows a very low reading in this interval. What is the most probable lithology?

Accepted Answer

Dolomite

Answer

Sandstone

Answer

Limestone

Answer

Anhydrite

Question 3

Archie's Law is fundamental for calculating water saturation (Sw). Which of the following parameters is NOT a direct component of the basic Archie equation (Sw^n = (a * Rw) / (Φ^m * Rt))?

Accepted Answer

Formation Temperature

Answer

Formation Water Resistivity (Rw)

Answer

Porosity (Φ)

Answer

True Formation Resistivity (Rt)

Question 4

A log analyst is evaluating a potential pay zone and needs to determine the lithology with high confidence, especially in a zone suspected to contain gas. Which logging measurement is least affected by the presence of gas and provides a strong indication of mineralogy?

Accepted Answer

Photoelectric Factor (Pe)

Answer

Neutron Porosity

Answer

Density Porosity

Answer

Sonic (Acoustic) Porosity

Question 5

In a well drilled with water-based mud, a resistivity log suite shows three curves: a shallow (SFL), a medium (ILM), and a deep (ILD) reading. In a permeable, hydrocarbon-bearing zone, what is the typical separation pattern observed among these curves?

Accepted Answer

SFL < ILM < ILD

Answer

ILD > ILM > SFL

Answer

SFL > ILM > ILD

Answer

ILD = ILM = SFL

Question 6

The bulk density (ρb) measured by a density log is a function of the matrix density (ρma), fluid density (ρf), and porosity (Φ). If a clean sandstone formation (ρma = 2.65 g/cm³) is completely saturated with fresh water (ρf = 1.00 g/cm³) and the density log reads a bulk density of 2.32 g/cm³, what is the calculated porosity?

Accepted Answer

20%

Answer

15%

Answer

25%

Answer

33%

A well is drilled with fresh mud (Rmf > Rw) into a sequence of formations.The Spontaneous Potential (SP) log shows a strong negative deflection against a thick, permeable sandstone formation.What is the most likely interpretation of this response?

A well is drilled with fresh mud (Rmf > Rw) into a sequence of formations.
The Spontaneous Potential (SP) log shows a strong negative deflection against a thick, permeable sandstone formation.
What is the most likely interpretation of this response?