I have been reading through a presentation on a new fracing technique that uses LP gas instead of water. With the EPA trying to outlaw conventional frac techniques I could see where this new technology could really take off. here is a link to the
Pressure (P) - psi
Pressure (psi) = Force (lb) / Area in Square Inch (in ^{2})
Pressure Gradient (G) - psi/ft
Mud Gradient ( Psi/ft ) = Mud weight ( PPG) x 0.052
Hydrostatic Pressure (HP) - psi
Hydrostatic Pressure (HP) = Mud weight (PPG) x 0.052 x TVD (ft)
You may have seen this triangle before but I need to emphasize on this because it will let you see all relationship of the hydrostatic pressure.
If you want to solve for MW or TVD, fill in the known information in these equations below;
Bottom Hole Pressure (BHP) - psi
Under static condition
Bottom Hole Pressure (BHP) = Hydrostatic Pressure (HP) + Surface Pressure (SP)
Under dynamic condition, use the following equation.
Bottom Hole Pressure (BHP) = Hydrostatic Pressure (HP) + Surface Pressure (SP) + Frictional Pressure (FrP)
Note: Frictional pressure acts opposite way of flow direction.
Formation Pressure (FP) - psi
After get Shut In Drill Pipe Pressure, you can calculate the formation pressure from this following relationship;
Formation Pressure (FP) = Hydrostatic Pressure (HP) + Shut-In Drill Pipe Pressure (SIDPP)
Equivalent Circulating Density (ECD) , ppg
Equivalent Circulating Density (ECD) ,ppg = (annular pressure loss, psi) ÷ 0.052 ÷ true vertical depth (TVD), ft + (current mud weight, ppg)
Leak-off Test Equivalent Mud Weight (LOT), ppg
Leak off test (ppg) = (Leak off test pressure in psi) ÷ 0.052 ÷ (Casing Shoe TVD in ft) + (Mud Weight used for LOT in ppg)
Maximum Initial Shut-In Casing Pressure (MISICP), psi
This calculation is based on shoe fracture which is equal to Leak Off Test Pressure.
MISICP (psi) = [LOT (ppg) – Current Mud Weight (ppg)] x 0.052 x Shoe TVD (ft)
Kill Mud Weight to Balance Formation (KMW), ppg
KWM (ppg) = [Shut In Drill Pipe Pressure (SIDP), psi ÷ (0.052x True Vertical Depth (TVD) of the well, ft)] + Original Mud Weight (ppg)
Slow Circulation Rate (SCR), psi
SCR (psi) = Initial Circulating Pressure (psi) – Shut In Drill Pipe Pressure (psi)
Annulus Capacity Factor (ACF),bbl/ft
Final Circulating Pressure (FCP), psi
Surface To Bit Strokes, strokes
Circulating Time, mins
Capacity Factor (CF), bbl/ft
Opened End Pipe Displacement, bbl/ft
Closed end pipe displacement, bbl/ft
Height of Influx, ft
Approximate gas migration rate, ft/hr
Sacks of Barite Required For Weight-up, sx
Volume Gain From Slug, bbl
Triplex Pump Output (volume), bbl/stroke
Pump Output, bbl/min
New Pump Pressure With New Pump Strokes, psi
Boyle’s Law - Gas Pressure and Volume Relationship
Mud Increment for Volumetric Method (MI), bbl
Lube Increment for Lubricate and Bleed Method (LI), bbl
Bottle Capacity Required, gal
Volume of Usable Fluid, gal
>
GasFrac_Investor_Presentation_June_2010.pdf.
Obvious benefits of LP fracs from the investor presentation include:
- LPG fracturing is a sustainable process for oil & gas operators by using products they produce to produce more hydrocarbons
- LPG fracturing eliminates the use of millions of gallons of potable water per well.
- LPG reduces the need to flare production to clean up the traditional fracturing fluids,eliminating thousands of tons of C02 emissions generating carbon credits that have a substantial dollar value
- Eliminates the disposal of millions of gallons of non potable frac water
- Eliminates the need for biocide chemicals that are required in fracturing
The list of possible benefits goes on-but I am wondering what the downside to fracing well with LPG might be. Depending on EPA rulings, this could turn into big business overnight.
I look forward to comments on this discussion
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