GATE-2018 (24) :Wyllie – Time average equation

GATE-2015

40. In a consolidated sandstone formation the interval transit times of the formation matrix and fluid are 70μm , 55μm and 190μm respectively. The porosity of the formation is .....

Solution:

The sonic tool measure the interval transit time(t),

porosity (Φ) =( Δt_log – Δt_mat )/ (Δt_fluid- Δt_mat) ------------------(1)

Δt_log – transit time of formation = 70 μs

Δt_mat – transit time of the matrix= 55 μs

Δt_fluid – transit time of fluid = 190 μs

above values substitute in eq(1)

Φ = (70-55) / (190-55)

Φ= 15 / 135

porosity(Φ) = 0.11