PEGN 102 Final Exam Studying

Question 1

What are two parameters needed to estimate the amount of oil in a reservoir?

Answer 1

Could be any # of things from res. Geometry (area, height – ones from class) porosity, Bo, water saturation (or oil saturation)

Question 2

Name the 3 geologic things necessary in order to have a petroleum reservoir.

Answer 2

Reservoir rock, source rock, trapping mech.

Question 3

Name two methods of reservoir evaluation?

Answer 3

Core sampling, cutting sampling, seismic, well logging –cased and openhole, LWD (logging well drilling), well test analysis, drill stem tests

Question 4

Who was a pioneer(s) of well logging in the oilfield industry?

Answer 4

Schlumberger, Marcel and Conrad

Question 5

What advantage does a PDC drill bit have over a rotary bit?

Answer 5

Made of sintered diamond pieces in polycrystalline diamond compacts as opposed to tungsten carbide/steel, lasts much longer, usually faster ROP, lower cost/foot effective drilling cost, no moving parts,

Question 6

Why is oil or gas migration important in exploration?

Answer 6

Can lead to discovery of an oil reservoir, by helping understand where the oil came from and its path from the source rock during paleo times.

Question 7

A “bright spot” on a seismic survey tells you what?

Answer 7

There maybe gas or other hydrocarbons

Question 8

Draw and label a vertical oil well with at least three cemented casing strings with perfs.

Answer 8

Just need perfs drawn in the Marcellus shale

Question 9

What is the uncontrolled influx of a fluid into a wellbore called?

Answer 9

KICK

Question 10

When talking about drill pipe, what is the difference between nominal weight per foot and actual weight per foot?

Answer 10

Nominal=just weight of pipe or tube, actual=weight of pipe (tube) + connections (tool joints)

Question 11

What are two examples of reservoir seals?

Answer 11

Top seals, lateral seals, fault seals, impermeable formation (salt shale)

Question 12

What is the difference between porosity and permeability?

Answer 12

Porosity-percentage of “pore space”. Relates grain density to bulk density.

Permeability- a measure of the ability of a material (such as rocks) to transmit fluids.

Porosity is not directional, permeability is.

Question 13

What is a major problem with using cuttings as a method of well sampling?

Answer 13

Cannot determine depth from where sample came from, difficult to interpret, dependent on skill of interpreter,

Question 14

Give your best definition of well logging?

Answer 14

The practice of making a detailed record (a well log) of the geologic formations penetrated by a borehole

Determination of seismic properties of rocks in boreholes by determining the velocities and the coefficients of reflection, transmittance, and absorption of elastic waves. (this may be a partial credit question)

Question 15

Give two purposes of casing strings, or liners.

Answer 15

Protects fresh water aquifers, anchors well control equipment, protects wells from transition zones (low and high pressured zones), protects holes from poor formations such as salts and sloughing shales

Question 16

Give an example of sedimentary facies.

Answer 16

Many options, both from list in slides and others. Must meet definition of facies

Question 17

What is a liner?

Answer 17

A casing string that does not extend to the top of the wellbore, but instead is anchored or suspended from inside the bottom of the previous casing string. There is no difference between the casing joints themselves. The advantage to the well designer of a liner is a substantial savings in steel, and therefore capital costs

Question 18

Give 1 example of a mobile land rotary drive drilling rig

Answer 18

Jackknife, portable mast, coil tubing

Question 19

What is a difference between an annular preventer and a pipe ram?

Answer 19

An annular preventer will be extruded (inflated?) hydraulically to close off irregular shapes, including the entire borehole. A pipe ram will seal around the pipe, but only a specific size, unless it is a variable bore pipe ram. Pipe rams are normally higher pressure rated than annular preventers.

Question 20

What is a purpose of surface casing?

Answer 20

Used to protect fresh water aquifers, support BOP etc….

Question 21

What is a difference between a structural trap and a stratigraphic trap?

Answer 21

Hydrocarbon traps that form in geologic structures such as folds and faults are called structural traps. Hydrocarbon traps that result from changes in rock type or pinch-outs, unconformities, or other sedimentary features such as reefs or buildups are called stratigraphic traps.

Question 22

Draw an anticline (something like this, most important to show the fold)

Answer 22

Question 23

Why would a whale appreciate the oil industry?

Answer 23

The oil industry was much cheaper that whale oil and destroyed the market for whale oil. No reason to hunt whales for their oil.

Question 24

What type of offshore drilling rig would you use in 5,000’ of water?

Answer 24

Drillship or semi-sub

Question 25

Why use drilling mud instead of just plain water?

Answer 25

Drilling mud can be made much denser (higher specific gravity) than water. This is needed to match the hydrostatic pressure of the formation to prevent formation fluids from entering the wellbore and protect the well. Drilling mud has better solids carrying capacity than water. Drilling mud will form a filter cake, water will leak off into a formation.