The following pressure measurements are made for a gas or oil reservoir.
Depth, m Pressure, MPa Fluid and density, kg/m3
2690 15.12 Gas, 410
2720 15.33 Oil, 820
2850 16.41 Water, 1040
a) Find the depth of the FWL and FOL.
𝑃𝑜 − 𝑃𝑔 + ⍴𝑔 𝑔𝑍𝑔 − ⍴𝑜 𝑔𝑍𝑜
𝑍𝐹𝑂𝐿 =
(⍴𝑔 − ⍴𝑜 )𝑔
(15.33 − 15.12)𝑋106 + ((410𝑋2690) − (820𝑋2720))(9.81)
𝑍𝐹𝑂𝐿 =
(410 − 820)(9.81)
= 2697.79𝑚
𝑃𝑤 − 𝑃𝑜 + ⍴𝑜 𝑔𝑍𝑜 − ⍴𝑤 𝑔𝑍𝑤
𝑍𝐹𝑊𝐿 =
(⍴𝑜 − ⍴𝑤 )𝑔
(16.41 − 15.33)𝑋106 + ((820𝑋2720) − (1040𝑋2850))(9.81)
𝑍𝐹𝑊𝐿 =
(820 − 1040)(9.81)
= 2834.13𝑚
b) Is the reservoir over-pressured, normal pressured or under-pressured?
The reservoir is under-pressured because
1040𝑘𝑔 9.81𝑚
𝑃𝑤 = 𝑃𝐴 + ⍴𝑤 𝑔ℎ = 101000 + 𝑋 𝑋 2850𝑚 = 29.18𝑀𝑃𝑎
𝑚3 𝑠2
➔ Which is higher than the actual water reservoir pressure of 16.41MPa.
Depth, m Pressure, MPa Fluid and density, kg/m3
2690 15.12 Gas, 410
2720 15.33 Oil, 820
2850 16.41 Water, 1040
a) Find the depth of the FWL and FOL.
𝑃𝑜 − 𝑃𝑔 + ⍴𝑔 𝑔𝑍𝑔 − ⍴𝑜 𝑔𝑍𝑜
𝑍𝐹𝑂𝐿 =
(⍴𝑔 − ⍴𝑜 )𝑔
(15.33 − 15.12)𝑋106 + ((410𝑋2690) − (820𝑋2720))(9.81)
𝑍𝐹𝑂𝐿 =
(410 − 820)(9.81)
= 2697.79𝑚
𝑃𝑤 − 𝑃𝑜 + ⍴𝑜 𝑔𝑍𝑜 − ⍴𝑤 𝑔𝑍𝑤
𝑍𝐹𝑊𝐿 =
(⍴𝑜 − ⍴𝑤 )𝑔
(16.41 − 15.33)𝑋106 + ((820𝑋2720) − (1040𝑋2850))(9.81)
𝑍𝐹𝑊𝐿 =
(820 − 1040)(9.81)
= 2834.13𝑚
b) Is the reservoir over-pressured, normal pressured or under-pressured?
The reservoir is under-pressured because
1040𝑘𝑔 9.81𝑚
𝑃𝑤 = 𝑃𝐴 + ⍴𝑤 𝑔ℎ = 101000 + 𝑋 𝑋 2850𝑚 = 29.18𝑀𝑃𝑎
𝑚3 𝑠2
➔ Which is higher than the actual water reservoir pressure of 16.41MPa.
