APPENDIX B

Calculations for Determining the Amount
of Drill-Water Intrusion

Use the following equations to determine the amount of drill-water intrusion in a sample:

,

where

P_S = integrated peak area of PFT in sample (in arbitrary units),

P_B = integrated peak area of PFT in blank (in arbitrary units),

a = slope derived from the calibration curve (in arbitrary units per gram),

C_DW = concentration of PFT in drilling fluid (in grams per liter),

W = weight of sample (in grams), and

F_I = fraction of the total headspace gas injected

,

where

V_inj = volume of sample injected (in liters),

V_vial = volume of vial (in liters),

_bulk = sample density (in grams per liter), and

W = weight of sample (in grams).

Example:

P_S = 995 arbitrary units

P_B = 566 arbitrary units

a = 1.1 × 10¹³ arbitrary units/g PFT

C_DW = 1 mg/L

W = 2.74 g

F_I = 0.3

V_inj = 5.0 mL

V_via = 20 mL

_bulk = 1.5 g/cm³

= 5.17 × 10^-8 L/g