Changes

'''''Example''''': Assume a leak-off test conducted in a 10,000-ft wellbore containing 11.5-ppg mud with a leak-off pressure of 1040 psi. The formation fracture pressure is estimated as

'''''Example''''': Assume a leak-off test conducted in a 10,000-ft wellbore containing 11.5-ppg mud with a leak-off pressure of 1040 psi. The formation fracture pressure is estimated as

:<math>\mbox{MW} = 1040/(0.052 \times 10{,}000 = 2.0 \mbox{ ppg}\end{align*}  $$</tex-math></disp-formula>

:<math>\mbox{MW} = 1040/(0.052 \times 10{,}000 = 2.0 \mbox{ ppg}</math>

The formation fracture pressure is equivalent to an 11.5 + 2.0 = 13.5 ppg mud weight, or<disp-formula><tex-math notation="TeX">$$\begin{align*}\mbox{FFP} = 0.052 \times 13.5 \times 10{,}000 = 7020 \mbox{ psi}</math>

The formation fracture pressure is equivalent to an 11.5 + 2.0 = 13.5 ppg mud weight, or

 

:<math>\mbox{FFP} = 0.052 \times 13.5 \times 10{,}000 = 7020 \mbox{ psi}</math>

Therefore, loss of circulation may be a problem in this wellbore if mud weights exceed about 13.5 ppg. This procedure is sufficiently accurate for quick field calculations, but it slightly overestimates the formation fracture pressures because the effective compressibility of the drilling fluid and frictional pressure losses are not accounted for.

Therefore, loss of circulation may be a problem in this wellbore if mud weights exceed about 13.5 ppg. This procedure is sufficiently accurate for quick field calculations, but it slightly overestimates the formation fracture pressures because the effective compressibility of the drilling fluid and frictional pressure losses are not accounted for.