gohfer variable sensitivity

8/10/2019 GOHFER Variable Sensitivity

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BASE MATCH OF SIMULATED DATA

Actual Data – Dashed Lines

Simulated Data – Solid Lines

35# HPG w/ 20/40 Badger Sand



PRESSURE COMPARISON - WIDTH EXPONENT = 2.8

Less pressure gain because of higher flow capacity in fracture.

Lower pressure drop down the fracture makes the final ISIP lower

than the base case. (appropriate for gelled treatments)





FRACTURE GEOMETRY COMPARISON – DECREASE IN WIDTH EXPONENT

Base Fracture Geometry

The created fracture geometry has less width because of the lower net pressure, and

generates longer length as the fluid can move more easily.



PRESSURE COMPARISON - WIDTH EXPONENT = 3.2

Increased pressure drop down the fracture makes the

pressure trend upward through the job and results in a

higher ISIP. (appropriate for slickwater treatments)





FRACTURE GEOMETRY COMPARISON – INCREASE IN WIDTH EXPONENT


The higher net pressure increases the fracture width and reduces length.



PRESSURE COMPARISON – TORTUOSITY = 100

Increase in observed treating pressure due to high near wellbore

pressure loss. Tortuosity erodes linearly with the mass of proppant

pumped. Early time treating pressure is more affected. ISIP has nochange as the tortuosity pressure drop disappears on shut-in.





FRACTURE GEOMETRY COMPARISON – INCREASE IN TORTUOSITY


No impact on fracture geometry



PRESSURE COMPARISON – CD = 0.5

Lower perforation entry coefficients (less efficient perforations)

leads to early increase in observed treating pressure. Addition of

proppant through perfs will increase coefficient. No change in ISIP.A much lower CD will generate a more rapid and almost exponential

decrease in treating pressure.





FRACTURE GEOMETRY COMPARISON – DECREASE IN COEFFICIENT OF

DISCHARGE





PRESSURE COMPARISON – CD = 0.9

Higher perforation entry coefficients (more efficient perforations)

leads to early decrease in observed treating pressure. Addition of

proppant through perfs will increase coefficient. No change in ISIP.





FRACTURE GEOMETRY COMPARISON – INCREASE IN COEFFICIENT OF

DISCHARGE





PRESSURE COMPARISON – MODULUS STIFFNESS = 0.001

Increase in the rate of modulus change when the rock yields non-

linearly results in an increase in the slope of the treating

pressure with time, once CFOP is exceeded. .





FRACTURE GEOMETRY COMPARISON – INCREASE IN MODULUS STIFFNESS


Higher modulus leads to higher stress and fracture pressure. Fracture may grow out of

zone resulting in lower average width and proppant concentration.



PRESSURE COMPARISON – MODULUS STIFFNESS = -0.001

Decrease in the rate of modulus change when the rock yields

non-linearly results in an decrease in the slope of the treating

pressure with time, once CFOP is exceeded.





FRACTURE GEOMETRY COMPARISON – DECREASE IN MODULUS

STIFFNESS


Lower modulus leads to lower stress and fracture pressure. Fracture width grows larger

and possibly shorter resulting in higher average proppant concentration.



PRESSURE COMPARISON – CXSP = 4 (DEFAULT - 2)

Higher pipe friction associated with the addition of proppant in

the pipe leads to increase in observed treating pressure. No

change in ISIP.





FRACTURE GEOMETRY COMPARISON – INCREASE IN SAND EXPONENT





PRESSURE COMPARISON – PHOLD = 1.7 (DEFAULT – 1.2)

Increase in proppant holdup proppant results in additional proppant

being held-up by interference with the fracture walls. Proppant is

traveling at a slower velocity compared to the fluid. Increase in

observed treating pressure but no screenout in this case.





FRACTURE GEOMETRY COMPARISON – INCREASE IN PHOLD


Higher PHOLD results in shorter fracture and higher average proppant concentration due to

more proppant being deposited near the wellbore.



PRESSURE COMPARISON – PHOLD = 2.2

Additional increase in proppant holdup proppant results in

earlier pressure increase and premature screenout (all

perforations blocked with proppant).





FRACTURE GEOMETRY COMPARISON – LARGER INCREASE IN PHOLD


Larger increase in PHOLD results in shorter fracture and higher average proppant

concentration due to more proppant being deposited near the wellbore and a screenout.



PRESSURE COMPARISON – PHOLD V/H FACTOR = 1.5

Increase in PHOLD vertical to horizontal anisotropy (V/H)

increases the proppant holdup vertically across layers resulting

in early pressure increase and premature screenout.





FRACTURE GEOMETRY COMPARISON – INCREASE IN PHOLD V/H FACTOR


Increase in PHOLD V/H Factor results in shorter fracture and higher average proppant

concentration due to more proppant being deposited (and distributed vertically) near the

wellbore and a screenout.



PRESSURE COMPARISON – PZS V/H FACTOR = 1.2

Increase in PZS vertical to horizontal anisotropy increases the net

fluid pressure over the PZS to grow vertically compared to

horizontally. May result in increased observed treating pressure

due to higher fracture pressure.





FRACTURE GEOMETRY COMPARISON – INCREASE IN PZS V/H FACTOR


Increase in PZS V/H Factor may result in longer more contained fracture. Negligible affect

on this example.

gohfer variable sensitivity

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