The answers are:

a$)=3000$ ppm

b$)=$Rm$=0\mathrm{.}08$ ohm$*$m

c$)=$Rmf$=1\mathrm{.}33$ ohm$*$m at $90$ F$.$

$=$Rmf$=0\mathrm{.}59$ ohm$*$m at $180$ F$.$

e$)=$Rmc$=0\mathrm{.}66$ ohm$*$m at $180$ F$.$

c$.$ Estimate the resistivities of the mud filtrate at $90$ and $180F.$

d$.$ Can you justify the statistical approximation for predominantly NaCl muds: $R_{mf}=0\mathrm{.}75R_m?$

e$.$ Estimate the resistivity of the mudcake at $180F.$

f$.$ Can you justify the statistical approximation for predominately NaCl muds: $R_{mc}=1\mathrm{.}5R_m?$

Determine the values of $R_m,R_{mf},$ and $R_{mc}$ at $10,000ft$ if mud weight $=16lb\frac{m}{g}al,$ mud resistivity $=0\mathrm{.}42*m$ at $75F,$ and geothermal gradient $=1\mathrm{.}1\frac{F}{100}ft.$

$4\mathrm{.}5$ At the time of logging$,$ the resistivity of a $10lb\frac{m}{g}al$ drilling mud is measured with an instrument on the surface. A value of $1\mathrm{.}52-$meter is obtained at a temperature of $90F.$

a$.$ What is the apparent salinity of the mud?

b$.$ What is the estimated mud resistivity at a depth of $8,600ft$ in the hole where the formation temperature is $180F?$