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Exercise 2 [3096] Calculation of effective vertical stress change An offshore sh

ID: 286589 • Letter: E

Question

Exercise 2 [3096] Calculation of effective vertical stress change An offshore shallow unconventional reservoir has a layer of sand at the top of the formation, which is overlaid by a layer of water of 10m thickness, as indicated in Figure 2. Calculate the change in effective vertical stress at a point A located at a depth of 6m from the top of the formation, as indicated in Figure 2, if the thickness of the water layer in the system increases by 8m. How can you explain your result? Final water level 8m Initial water level 10m Pnater= 1000kg/m Layer of sand 6m Psand 2100kg/m Figure 2. Schematic diagram of the system considered in Exercise 2.

Explanation / Answer

unit weight of water, w = 9.8 kN/m3

Total Stress at point A = 9.8x8 + 1000x9.8x10 + 2100x 9.8 x 6

=221558.4  kN/m3