3 Determine overburden gradient at various depths for the following offshore well PDF

Title	3 Determine overburden gradient at various depths for the following offshore well
Author	Peter van der Burg
Course	Petroleum Engineering Principles
Institution	University of Portsmouth
Pages	2
File Size	53.4 KB
File Type	PDF
Total Downloads	19
Total Views	126

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Drilling Engineering...

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Determine overburden gradient at various depths for the following offshore well Water Depth : 100m, RKB/MSL: 20m Specific Gravity of Sea Water: 1.04gm/cc Rock Density : 1.8gm/cc from seabed to 1000ft, 2.1gm/cc from 1000ft-2500ft and 2.85 from 2500-4000 Calculate overburden gradient at seabed, 500 ft , 1000ft, 2800ft and 4000ft. Convert water depth and RKB/MSL to ft. 1m= 3.28 ft water depth= 100X3.28= 328 RKB/MSL = 20X 3.28= 65.6 ft

Convert densities from gm/cc to psi/ft using Equation Gradient (psi/ft) = 0.433 x (gm /cc). a. At seabed Water pressure = 0.433 (psi/ft) x 1.04 (gm/cc) x 328 (ft) = 147.7 psi Overburden gradient (OBG) = water pressure / depth = 147.7/ (328+65.6) = 0.375 psi/ft OBG/0.052= ppg = 0.375/0.052 =7.2 ppg b. At 500 ft below seabed Water pressure= 147.7 psi Weight of formation= 0.433 x 1.8 x 500 ft = 389.7 psi Overburden gradient (OBG) = total weight of sea water and rocks /total depth = (147.7 + 389.7)/ (328+65.6+500)= 0.601 psi/ft = 11.56 ppg c. At 1000 ft below seabed Water pressure= 147.7 psi Weight of formation= 0.433 x 1.8 x 1000 ft = 779.4 psi Overburden gradient (OBG) = total weight of sea water and rocks /total depth = (147.7 + 779.4)/ (328+65.6+1000) = 0.665 psi/ft = 12.8 ppg d. At 2800 ft below seabed Water pressure = 147.7 psi Weight of formation = 0.433 x 1.8 x1000 ft = 779.4 psi =0.433x2.1x1500ft=1363.95 psi =0.433x2.85x300=370.21psi Overburden gradient (OBG) = total weight of sea water and rocks /total depth = (147.7 + 779.4+1363.95+370.2)/ (328+65.6+ 2800) = 0.833 psi/ft = 16.02 ppg e. At 4000 ft below seabed Water pressure =147.7 psi Weight of formation (with density of 1.8 gm/cc)= 0.433 x 1.8 x1000 ft = 779.4 psi Weight of formation (with density of 2.1 gm/cc)= 0.433 x 2.1 x1500 ft = 1363.95 psi Weight of formation (with density of 2.1 gm/cc)= 0.433 x 2.85 x1500 ft = 1851.6 psi Overburden gradient (OBG) = total weight of sea water and rocks /total depth = (147.7+779.4+1363.95+1851.6)/ (328+65.6+4000) =0.942 psi/ft = 18.13 ppg...