Page 310 - Well Control for Completions and Interventions

302 Well Control for Completions and Interventions

Casing volume (from tail-pipe to the perforations)5 0.03713 1905 7bbls.
Total volume 153 1 7 5 160 bbls.
3. Calculate the kill fluid density and gradient needed to achieve a
200 psi overbalance at the end of the kill.
5747 1 200
Kill fluid ppgÞ 5 5 10:94-11 ppg:
ð
10; 450 3 0:052
11 ppg 3 0:052 5 0:572 psi=ft:
4. Calculate the maximum volume of fluid that can be pumped without
exceeding the formation fracture pressure (including the designated
safety margin). The method used in this example first calculates the
approximate pressure increase (downhole) with each barrel pumped.
Separate calculations for the casing and tubing are required since the
hydrostatic head increase will be different.
a. Approximate pressure increase per bbl of fluid pumped due to gas
compression.
5747 3 160
Pressure after pumping 1 bbl 5
159
5 5783 psi: ð5783 2 5747 5 36 psi increaseÞ
Note: The increase at surface after pumping 1 bbl is 31 psi due
to the lower starting (P_1) pressure 4911 psi.
b. Hydrostatic pressure increase, per bbl of kill fluid pumped.
Tubing: 1/0.0149 5 67 ft/bbl. 67 3 (0.572 0.08) 5 33 psi/bbl.
Casing: 1/0.0371 5 27 ft/bbl. 27 3 (0.572 0.08) 5 13 psi/bbl.
Approximate pressure increase (at reservoir) per bbl pumped.
Tubing: 36 (gas compression) 1 33 (hydrostatic head) 5 69 psi.
Casing: 36 (gas compression) 1 13 (hydrostatic head) 5 49 psi.
Maximum pressure at reservoir depth is fracture pressure minus the
safety margin (6950 500 5 6450 psi). The maximum permitted
pressure increase is maximum allowable pressure minus reservoir
pressure: 6450 5747 5 703-700 psi.
700/69 5 10.14-10 bbls of kill fluid in the tubing.
700/49 5 14.28-14 bbls of kill fluid in the casing.
5. Since the casing volume (from tubing end to reservoir depth) is
7 bbls, pumping the maximum calculated volume of 14 bbls would
place 7 bbls of kill fluid in tubing, exceed the allowable maximum