Question

Fig. 1.31-Unit block of porous medium of Problem 1.2

Answer 1

Length of rock = l = L Length (effective length) of hole = L_e = L (Therefore hole is made stright) Side of the square = d Diameter of hole = d Area of cross section of rock = A A = A_Total - A_hole A = d^2 - pi d^2/4 = (4 - pi/4) d^2 Cross section of hole 'a' = pi d^2/4 Formation resistivity of the block (F) F = R_0/R_w [R_0 = Resistivity of fully water saturated rock R_w = saturating water resistivity R_0 = r_0 A/L r_0 = R_w L/a e R_0 (R_w L_e/a) A/L = > R_0/R_w = F = L_e/L times A/a = A/a (i) (Therefore L_e = L) F = (4 - pi/4) d^2/pi/4 d^2 = 4 - pi/pi = 4/pi - 1 F TildeFullEqual 1.27388 - 1 (Taking pi = 3.14) F TildeFullEqual 0.27388 (Formation Resistivity) Porosity phi = a/A Formation Resistivity F = A/a from (i)