Module 1- Log Analysis Findamentals

Question 1

What 3 things do we need to find out in a well log?

Answer 1

Rock Type, Rock Properties, Fluids

Question 2

What is a well log?

Answer 2

A continuous record of measurements made in bore hole to detect variations of some physical properties of the subsurface rocks.

Question 3

What are the 5 properties of the rock that logging is trying to determine?

Answer 3

Porosity
Permeability
Bedding Orientation
Fractures
Temperature

Question 4

What are the 4 fluid properties logging is trying to determine?

Answer 4

Type
Saturation
Salinity
Pressure

Question 5

What information can be determined from drill cuttings?

Answer 5

rock type
HC indications
Porosity type

Question 6

What information can be determined from mud logs?

Answer 6

drilling rate
mud properties
gas analysis

Question 7

What information can be determined from pressure transient tests?

Answer 7

reservoir pressure
permeability and skin
fluid recovery

Question 8

What information can be determined from cores?

Answer 8

porosity
permeability
lithology
residual fluid saturations

Question 9

What information can be determined from well logs?

Answer 9

Porosity
lithology
water saturation
net pay thickness

Question 10

What information can be determined from Seismic data?

Answer 10

structure
gross and net thickness
porosity

Question 11

What is the only logging method that is considered to have definitive results?

Answer 11

Cores!

Question 12

Open hole logging tools are also called?

Answer 12

Sondes

Question 13

what are triple-combo & platform Express tools?

Answer 13

Modern wireline logging tools that run resistivity and porosity tools at the same time.

Triple combo-90ft
platform express- 38ft

Question 14

The triple-combo & platform express tools each contain what?

Answer 14

Resistivity Log

Two porosity logs

Question 15

What are passive measurements?

Answer 15

may be made of naturally occurring phenomena like radioactivity

Question 16

What are active measurements?

Answer 16

may be induced, as is the case with an induction resistivity log, for example.

Question 17

What are the 3 broad categories of open hole logs?

Answer 17

Natural detection
Porosity
Resistivity

Question 18

What are the 2 natural detection logs?

Answer 18

Spontaneous Potential

Gamma Ray

Question 19

What does Spontaneous Potential measure?

Answer 19

Measures natural electric potential generated in the rock, showing porous and permeable beds.

SHALE OR NON-SHALE INDICATOR

Question 20

what do Gamma Ray logs measure?

Answer 20

measures natural radiation from unstable elements (uranium, thorium, potassium)

Question 21

What would a good gamma ray lithology log read?

Answer 21

identifies shale clearly by HIGH gamma ray readings.

identifies Sandstone & carbonates by LOW gamma ray readings.

Question 22

What are the 3 logs used to calculate porosity?

Answer 22

Neutron (emits neutrons)
Density (emits gamma rays)
Sonic (emits sound waves)

Question 23

What does a neutron log measure?

Answer 23

Hydrogen concentration in the formation

Question 24

What does a density log measure?

Answer 24

measures the weakening of gamma rays and calculates bulk density of the formation

Question 25

What does a sonic log measure?

Answer 25

transit time of sound waves through formation

Question 26

Define resistivity

Answer 26

ability of a material to resist electrical conduction. Inverse of conductivity. Measured in Ohm-m.

Question 27

What are the 2 resistivity logs?

Answer 27

Induction log

Laterolog

Question 28

What does an induction lot measure?

Answer 28

measures resistivity indirectly by measuring conductivity

Question 29

What does a laterolog(focused log) measure?

Answer 29

measures resistivity of formation by passing a current between two electrodes.

Question 30

T or F: The induction and Laterolog are commonly run together?

Answer 30

TRUE

Question 31

What do the following abbreviation stand for? (terminologies used in a borehole environments/well logging)

dh
di/dj
Rmf
Rxo
Sxo
Rw
Rt
Sw

Answer 31

dh- hole diameter
di/dj- invasion diameters
Rmf- mud filtrate resistivity
Rxo- flushed zone resistivity
Sxo- flushed zone saturation
Rw- formation water resistivity
Rt- uninvaded zone resistivity
Sw- water saturation

Question 32

What are 6 things that open hole well logs are used for?

Answer 32

1. Detect hydrocarbons
2. Determine lithology
3. Evaluate zones
4. Correlation zones
5. Determine dip, faults and other geologic structures
6. identifies sedimentary environments of deposition

Question 33

Explain methods used in both open hole and cased hole well logs.

Answer 33

Open hole logging tools are attached to a wire-line and run to the bottom of the hole. The tool is slowly pulled upwards and the tool response is sent through the wireline to the truck where it is recorded.

Alternatively, the logging sensor may be embedded in the drill string and is LWD.

Question 34

What is high-tension conveyance & wireline deployment and why is it used?

Answer 34

condition associated with deep, highly deviated well paths that are managed by using systems that pair high-stregth cable with specialized surface equipment.

conveyance of most logging tools on drill-pipe, coiled tubing or wireline tractors is also available