SLB Glossary

Question 1

ECD

Answer 1

The effective density exerted by a circulating fluid against the formation that takes into account the pressure drop in the annulus above the point being considered.

Question 2

What is the normal hydrostatic pressure gradient for freshwater?

Answer 2

0.433 psi/ft

Question 3

How does permeability affect formation pressure?

Answer 3

When impermeable rocks such as shales form as sediments are compacted, their pore fluids cannot always escape and must then support the total overlying rock column, leading to anomalously high formation pressures

Question 4

What is permeability?

Answer 4

The ability of a rock to transmit fluids

Question 5

Is sandstone permeable?

Answer 5

Yes, tends to have large interconnected pores

Question 6

Is shale permeable?

Answer 6

No, tend to be finer grained with smaller, fewer or less interconnected pores.

Question 7

Is siltstone permeable?

Answer 7

No, tend to be finer grained with smaller, fewer or less interconnected pores.

Question 8

What type of rock is more desirable for reservoirs - permeable or impermeable?

Answer 8

Impermeable. Hydrocarbons cannot pass through them readily.

Question 9

Porosity

Answer 9

The percentage of pore volume or void space, or that volume within rock that can contain fluids.

Question 10

Effective porosity

Answer 10

the interconnected pore volume in a rock that contributes to fluid flow in a reservoir. It excludes isolated pores.

Question 11

Total porosity

Answer 11

the total void space in the rock whether or not it contributes to fluid flow.

Question 12

What is the porosity/permeability composition of shale?

Answer 12

Shale gas reservoirs tend to have relatively high porosity, but the alignment of platy grains such as clays makes their permeability very low.

Question 13

What is pore pressure?

Answer 13

The pressure of fluids within the pores of a reservoir, usually hydrostatic pressure, or the pressure exerted by a column of water from the formation’s depth to sea level.

Question 14

What is fracture pressure?

Answer 14

The pressure required to induce fractures in rock at a given depth.

Question 15

What does a LOT determine?

Answer 15

the maximum pressure or mud weight that may be applied to the well during drilling operations.

Question 16

When is a LOT performed?

Answer 16

usually conducted immediately after drilling below a new casing shoe.

Question 17

How is a LOT performed?

Answer 17

the well is shut in and fluid is pumped into the wellbore to gradually increase the pressure that the formation experiences. At some pressure, fluid will enter the formation, or leak off, either moving through permeable paths in the rock or by creating a space by fracturing the rock.

Question 18

What is a leak-off test?

Answer 18

Test to determine the strength or fracture pressure of the open formation

Question 19

What is another name for a leak-off test?

Answer 19

Pressure integrity test (PIT)

Question 20

In cementing, where does bottom plug land?

Answer 20

Float collar or landing collar

Question 21

Hydrostatic pressure

Answer 21

predicted pressure for a given depth, or the pressure exerted per unit area by a column of freshwater from sea level to a given depth

Question 22

What happens to formation pressure in depleted hydrocarbon reservoirs?

Answer 22

Abnormally low pressure might occur in areas where fluids have been drained

Question 23

Examples of high gravity solids

Answer 23

Barite, hematite, calcium carbonate

Question 24

Plastic viscosity

Answer 24

A fluid’s resistance to flow

Question 25

Funnel viscosity

Answer 25

Time it takes for 1 qt of mud to flow through marsh funnel

Question 26

Use of funnel viscosity?

Answer 26

this measurement of the mud viscosity is useful because it is a quick and simple test for observing trends of drilling mud. In order to use the funnel viscosity effectively, personnel must record the values frequently. Then looking at a trend of funnel viscosity, it will indicate if there is any issue with drilling mud

Question 27

What increases plastic viscosity?

Answer 27

Any increase in solid content in drilling mud such as barite, drill solid, lost circulation material, etc., will result in higher plastic viscosity.

Question 28

Correlation between MW and PV

Answer 28

Normally, the higher the mud weight, the higher plastic viscosity will be.

Question 29

Ballooning theory

Answer 29

occurs when frac stress is greater than the mud weight but less than ECD

Question 30

What happens when a well balloons?

Answer 30

With pumps off, the well stands full in the static condition. However, fracture extends and takes mud when circulation is established since ECD exceeds the fracture closure stress. When the pumps are stopped and ECD removed, the fracture closes, forcing some or all the mud back into the wellbore.

Question 31

Low gravity solids

Answer 31

Also known as drilled solids.

Question 32

Example of LGS

Answer 32

Rock cuttings

Question 33

Primary well control

Answer 33

Hydrostatic pressure

Question 34

Secondary well control

Answer 34

BOP

Question 35

Tertiary well control

Answer 35

Relief well dynamic kill pump barite, gunk or cement to plug well

Question 36

Benefits of underbalanced drilling

Answer 36

Underbalanced conditions do not allow filter cake build-up and also avoid formation damage due to the invasion of drilling mud and solids into the formation