Intro to Stimulation: Calculation Definitions

Question 1

Absolute Permeability

Answer 1

the D’arcy’s Law permeability

Question 2

Absolute Volume Factore

Answer 2

typically refers to the units of gallons per pound (liters per kilogram). This is the absolute volume that a solid will take up in water.

Question 3

Barrel

Answer 3

Oil field barrel is 42 gallons.

Question 4

BHTP

Answer 4

Bottom Hole Treating Pressure; the amount of pressure required at the perforations to cause fracture extension. Many times this value is reported as the “frac gradient.” The gradient is calculated by dividing the BHTP by the depth to the center of the perforations.

Question 5

bbl/min

Answer 5

refers to the pump rate or Barrels per Minute (use bpm instead of bbl/min).

Question 6

bpm

Answer 6

refers to the pump rate of Barrels per Minute

Question 7

Closure Pressure

Answer 7

the fluid pressure required to reopen an exiting fracture. This pressure is equal to, and counteracts, the stress in the rock perpendicular to the fracture plane. This stress is the minimum principal in-situ stress and is often called the closure stress.

Question 8

Clean Volume

Answer 8

refers to the volume of the treating fluid without taking into account proppant.

Question 9

D’arcy’s Law

Answer 9

applies to linear flow, such as flow through a sand plug in casing:

Question 10

Density

Answer 10

the mass per unit volume of a given body. Water density is 8.33 lb per gallon at 70°F.

Question 11

Dirty Volume

Answer 11

the “clean” volume plus the volume of the proppant.

Question 12

Effective Permeability

Answer 12

the permeability to one fluid in a multi-fluid system and is a function of the fluid saturation.

Question 13

Flash Point

Answer 13

the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to spark or flame.

Question 14

Frace Gradient

Answer 14

(Hydrostatic pressure at perforation mid point + ISIP) divided by depth of perforation mid point.

Question 15

ISIP

Answer 15

P_ISIP; the instantaneous shut in pressure. It can be determined during a pump-in test. The pumps are brought on line at a rate that will cause the formation to fracture (“break down”). Fluid is pumped into the formation for a short time then pumping is stopped. Reflects the amount of pressure recorded immediately after shutting the pumps down. Values can be hard to determine if the bottom hole slurry rate is not zero and/or water hammer is introduced. Graphical methods are used to determine an ISIP when water hammer is present by extrapolating back along a straight line section to the intersection of the first oscillation of the water hammer.

Question 16

HHP

Answer 16

Hydraulic Horsepower; a unit of measurement for the amount of work that is or can be done by hydraulic equipment. Can be calculated by (pressure X rate)/40.8.

Question 17

Mgal

Answer 17

the M is the Roman numeral for one-thousand. Therefore, this refers to Thousands of Gallons. Used in concentration statements.

Question 18

Net Pressure

Answer 18

the difference in ISIP pressure and closure pressure.

Question 19

Permeability

Answer 19

a function of the geometry, configuration, and scalar dimensions of the voids or pores and is not as such a physical property derived from a dynamic system.

Question 20

P_h

Answer 20

Hydrostatic Pressure, the pressure exerted at the bottom of a fluid column.

Question 21

P_w

Answer 21

Wellhead Pressure; the gauge measured treating pressure at the surface.

Question 22

ΔP_frict

Answer 22

the pressure loss due to friction in the pipe. Movement of fluid past a stationary object causes this friction, which in this case is the pipe wall.

Question 23

P_perf

Answer 23

Perforation Frictions; the friction loss caused by fluid flow through a perforation or group of perforations.

Question 24

Porosity

Answer 24

a fractional or percentage value referring to the void spaces inside a rock or the part of the rock that is not rock.

Question 25

Relative Permeability

Answer 25

the ratio of the effective permeability to the absolute permeability of the porous medium.

Question 26

Slurry Volume

Answer 26

the total volume of fluid, additives, and proppants. This reflects the total volume of fluid that is pumped. Also referred to as Dirty Volume

Question 27

Specific Gravity

Answer 27

a unit-less ratio relationship between a substance and a base substance. For liquids, the base is water. For gases, air is the base substance.

Question 28

Temperature Gradient

Answer 28

defines a linear relationship of temperature to depth.