Basic Hydraulic Fracturing Calculations

Today we will take a look at the basic calculations that you might need to perform during hydraulic fracturing operations to find rates, pressure, and volumes.

Calculating Frac Gradient

Frac Gradient = (ISIP + hydrostatic pressure)/TVD

TVD – True vertical depth

ISIP – Instantaneous shut-in Pressure = Final injection pressure – Pressure drop due to friction

ISIP is taken right after pumps are shut down

The frac gradient is used to calculate the pressure needed to break the formation and initiate the fracture.

Related: What is Proppant in Oil and Gas?

>

Calculating Wellhead Pressure (WHP)

WHP = BHFP – hydrostatic pressure + friction pressure

Bottom Hole Fracturing Pressure (BHFP) = Frac Gradient x Depth (TVD)=ISIP + Hydrostatic pressure

Bottom Hole Pressure (BHP) = Hydrostatic pressure +WHP

Hydrostatic Pressure = fluid density x 0.00981 x Depth (TVD)

Friction Pressure = Friction gradient x Depth (TMD) + Perforation Friction +Near wellbore Friction

TMD – Total measured depth

Related: What is Hydraulic Fracturing?

Calculating Flush Volumes

Flush Volume = Perf Depth x Tubing Internal Capacity

Flush volume is usually equal to the full wellbore volume of fluid that is pumped to displace all the proppant.

Overflush means that more than the wellbore volume is pumped.

Calculating Sand and Slurry Rates

Slurry Rate = Clean Rate x (1 +(Proppant concentration/SG))

Slurry rate is the total rate combined of fluid, chemicals, and proppant

Clean Rate – the pumping rate before the proppant is added

Dirty Rate – the total slurry pumping rate with proppant

Proppant Concentration = ((Slurry Rate – Clean Rate)/Clean Rate) x SG (Proppant)

Proppant concentration is the sand concentration in the fracturing fluid

Sand Pumped = (Dirty Rate – Clean Rate) x SG of Sand

The specific gravity of sand is 2650 kg/m3

N2 Downhole Rate (m3/min) = N2 Rate (scm/min)/N2 Volume Factor (scm/min)

Horse Power Calculations

Pumping Power (kW)=(Pump rate (m3/min) x WHP (kPa))/60

Pumping Power (HP) =Pumping Power (kW) x 1.341

HP – Horse Power

Read next: Top 10 Chemicals Used In Hydraulic Fracturing Process

References:

http://www.fekete.com/SAN/TheoryAndEquations/WellTestTheoryEquations/ISIP.htm

Related Articles

Latest Articles