Section 2. Calculation Formula

  1. Hydrostatic pressure (psi)
fluid density (ppg)×0.052×TVD (ft)\text{fluid density (ppg)} \times 0.052 \times \text{TVD (ft)}
  1. Pressure gradient (psi/ft)
fluid density (ppg)×0.052\text{fluid density (ppg)} \times 0.052
  1. Fluid density (ppg)
hydrostatic pressure (psi)÷TVD (ft)÷0.052\text{hydrostatic pressure (psi)} ÷ \text{TVD (ft)} ÷ 0.052

or

hydrostatic pressure (psi)TVD (ft)×0.052\frac {\text{hydrostatic pressure (psi)}} {\text{TVD (ft)} \times 0.052}
  1. Formation pressure (psi)
hydrostatic pressure in drillstring (psi)+SIDPP (psi)\text{hydrostatic pressure in drillstring (psi)} + \text{SIDPP (psi)}
  1. Pump output (bbl/min)
pump displacement (bbl/stroke)×pump rate (SPM)\text{pump displacement (bbl/stroke)} \times \text{pump rate (SPM)}
  1. Equivalent circulation density (ppg)
fluid density (ppg)+(annular pressure loss (psi)÷TVD (ft)÷0.052)\text{fluid density (ppg)} + (\text{annular pressure loss (psi)} ÷ \text{TVD (ft)} ÷ 0.052)

or

fluid density (ppg)+(annular pressure loss (psi)TVD (ft)×0.052)\text{fluid density (ppg)} + \left( \frac {\text{annular pressure loss (psi)}} {\text{TVD (ft)} \times 0.052} \right)
  1. Fluid density (ppg) with trip margin (psi) included
fluid density (ppg)+(trip margin (psi)÷TVD (ft)÷0.052)\text{fluid density (ppg)} + (\text{trip margin (psi)} ÷ \text{TVD (ft)} ÷ 0.052)

or

fluid density (ppg)+(trip margin (psi)TVD (ft)×0.052)\text{fluid density (ppg)} + \left( \frac {\text{trip margin (psi)}} {\text{TVD (ft)} \times 0.052} \right)
  1. New pump pressure (psi) with new pump rate (SPM) (approximate)
current pump pressure (psi)×(new pump rate (SPM)current pump rate (SPM))2\text{current pump pressure (psi)} \times \left( \frac {\text{new pump rate (SPM)}} {\text{current pump rate (SPM)}} \right) ^2
  1. New pump pressure (psi) with new fluid density (ppg) (approximate)
current pump pressure (psi)×(new fluid density (ppg)current fluid density (ppg))\text{current pump pressure (psi)} \times \left( \frac {\text{new fluid density (ppg)}} {\text{current fluid density (ppg)}} \right)
  1. Maximum allowable fluid density (ppg)
LOT fluid density (ppg)+(surface LOT pressure (psi)÷casing shoe TVD (ft)÷0.052)\text{LOT fluid density (ppg)} + (\text{surface LOT pressure (psi)} ÷ \text{casing shoe TVD (ft)} ÷ 0.052)

or

LOT fluid density (ppg)+(surface LOT pressure (psi)casing shoe TVD (ft)×0.052)\text{LOT fluid density (ppg)} + \left( \frac {\text{surface LOT pressure (psi)}} {\text{casing shoe TVD (ft)} \times 0.052} \right)
  1. MAASP (psi)
(maximum allowable fluid density (ppg)−current fluid density (ppg))×casing shoe TVD (ft)×0.052(\text{maximum allowable fluid density (ppg)} - \text{current fluid density (ppg)}) \times \text{casing shoe TVD (ft)} \times 0.052
  1. Kill fluid density (ppg)
current fluid density (ppg)+(SIDPP (psi)÷TVD (ft)÷0.052)\text{current fluid density (ppg)} + (\text{SIDPP (psi)} ÷ \text{TVD (ft)} ÷ 0.052)

or

current fluid density (ppg)+(SIDPP (psi)TVD (ft)×0.052)\text{current fluid density (ppg)} + \left( \frac {\text{SIDPP (psi)}} {\text{TVD (ft)} \times 0.052} \right)
  1. Initial circulating pressure (psi)
circulating pressure at kill rate (psi)+SIDPP (psi)\text{circulating pressure at kill rate (psi)} + \text{SIDPP (psi)}
  1. Final circulating pressure (psi)
(kill fluid density (ppg)current fluid density (ppg))×circulating pressure at kill rate (psi)\left( \frac {\text{kill fluid density (ppg)}} {\text{current fluid density (ppg)}} \right) \times \text{circulating pressure at kill rate (psi)}
  1. Gas migration rate (ft/hr)
rate of increase in surface pressure (psi/hr)÷fluid density (ppg)÷0.052\text{rate of increase in surface pressure (psi/hr)} ÷ \text{fluid density (ppg)} ÷ 0.052

or

rate of increase in surface pressure (psi/hr)fluid density (ppg)×0.052\frac {\text{rate of increase in surface pressure (psi/hr)}} {\text{fluid density (ppg)} \times 0.052}
  1. Gas laws
P1×V1=P2×V2P_{1} \times V_{1} = P_{2} \times V_{2}
P1=P2×V2V1P_{1} = \frac {P_{2} \times V_{2}} {V_{1}}
P2=P1×V1V2P_{2} = \frac {P_{1} \times V_{1}} {V_{2}}
V1=P2×V2P1V_{1} = \frac {P_{2} \times V_{2}} {P_{1}}
V2=P1×V1P2V_{2} = \frac {P_{1} \times V_{1}} {P_{2}}
  1. Pressure drop per foot tripping dry pipe (psi/ft)
fluid density (ppg)×0.052×metal displacement (bbl/ft)riser or casing capacity (bbl/ft)−metal displacement (bbl/ft)\frac {\text{fluid density (ppg)} \times 0.052 \times \text{metal displacement (bbl/ft)}} {\text{riser or casing capacity (bbl/ft)} - \text{metal displacement (bbl/ft)}}
  1. Pressure drop per foot tripping wet pipe (psi/ft)
fluid density (ppg)×0.052×closed end displacement (bbl/ft)riser or casing capacity (bbl/ft)−closed end displacement (bbl/ft)\frac {\text{fluid density (ppg)} \times 0.052 \times \text{closed end displacement (bbl/ft)}} {\text{riser or casing capacity (bbl/ft)} - \text{closed end displacement (bbl/ft)}}
  1. Level drop pulling remaining collars out of well dry (ft)
length of collars (ft)×metal displacement (bbl/ft)riser or casing capacity (bbl/ft)\frac {\text{length of collars (ft)} \times \text{metal displacement (bbl/ft)}} {\text{riser or casing capacity (bbl/ft)}}
  1. Level drop pulling remaining collars out of well wet (ft)
length of collars (ft)×closed end displacement (bbl/ft)riser or casing capacity (bbl/ft)\frac {\text{length of collars (ft)} \times \text{closed end displacement (bbl/ft)}} {\text{riser or casing capacity (bbl/ft)}}
  1. Length of tubulars to pull dry before overbalance is lost (ft)
overbalance (psi)×(riser or casing capacity (bbl/ft)−metal displacement (bbl/ft))fluid gradient (psi/ft)×metal displacement (bbl/ft)\frac {\text{overbalance (psi)} \times \left( \text{riser or casing capacity (bbl/ft)} - \text{metal displacement (bbl/ft)} \right)} {\text{fluid gradient (psi/ft)} \times \text{metal displacement (bbl/ft)}}

or

overbalance (psi)×(riser or casing capacity (bbl/ft)−metal displacement (bbl/ft))fluid density (ppg)×0.052×metal displacement (bbl/ft)\frac {\text{overbalance (psi)} \times \left( \text{riser or casing capacity (bbl/ft)} - \text{metal displacement (bbl/ft)} \right)} {\text{fluid density (ppg)} \times 0.052 \times \text{metal displacement (bbl/ft)}}
  1. Length of tubulars to pull wet before overbalance is lost (ft)
overbalance (psi)×(riser or casing capacity (bbl/ft)−closed end displacement (bbl/ft))fluid gradient (psi/ft)×closed end displacement (bbl/ft)\frac {\text{overbalance (psi)} \times \left( \text{riser or casing capacity (bbl/ft)} - \text{closed end displacement (bbl/ft)} \right)} {\text{fluid gradient (psi/ft)} \times \text{closed end displacement (bbl/ft)}}

or

overbalance (psi)×(riser or casing capacity (bbl/ft)−closed end displacement (bbl/ft))fluid density (ppg)×0.052×closed end displacement (bbl/ft)\frac {\text{overbalance (psi)} \times \left( \text{riser or casing capacity (bbl/ft)} - \text{closed end displacement (bbl/ft)} \right)} {\text{fluid density (ppg)} \times 0.052 \times \text{closed end displacement (bbl/ft)}}
  1. Volume to bleed due to gas migration in a vertical well (bbl)
working pressure to bleed (psi)×(annular capacity (bbl/ft)pressure gradient (psi/ft))\text{working pressure to bleed (psi)} \times \left( \frac {\text{annular capacity (bbl/ft)}} {\text{pressure gradient (psi/ft)}} \right)

or

working pressure to bleed (psi)×(annular capacity (bbl/ft)fluid density (ppg)×0.052)\text{working pressure to bleed (psi)} \times \left( \frac {\text{annular capacity (bbl/ft)}} {\text{fluid density (ppg)} \times 0.052} \right)
  1. Slug volume (bbl) for a given length of dry pipe
length of dry pipe (ft)×pipe capacity (bbl/ft)×current fluid density (ppg)slug density (ppg)−current fluid density (ppg)\frac {\text{length of dry pipe (ft)} \times \text{pipe capacity (bbl/ft)} \times \text{current fluid density (ppg)}} {\text{slug density (ppg)} - \text{current fluid density (ppg)}}
  1. Pit gain due to slug U-tubing (bbl)
slug volume (bbl)×(slug density (ppg)current fluid density (ppg)−1)\text{slug volume (bbl)} \times \left( \frac {\text{slug density (ppg)}} {\text{current fluid density (ppg)}} - 1 \right)
  1. Riser margin (ppg)
(air gap (ft)+water depth (ft))×fluid density (ppg)−(water depth (ft)×water density (ppg))TVD (ft)−air gap (ft)−water depth (ft)\frac {\left(\text{air gap (ft)} + \text{water depth (ft)}\right) \times \text{fluid density (ppg)} - \left(\text{water depth (ft)} \times \text{water density (ppg)}\right)} {\text{TVD (ft)} - \text{air gap (ft)} - \text{water depth (ft)}}
  1. Hydrostatic pressure loss if casing float fails (psi)
fluid density (ppg)×0.052×casing capacity (bbl/ft)×unfilled casing height (ft)casing capacity (bbl/ft)+annular capacity (bbl/ft)\frac {\text{fluid density (ppg)} \times 0.052 \times \text{casing capacity (bbl/ft)} \times \text{unfilled casing height (ft)}} {\text{casing capacity (bbl/ft)} + \text{annular capacity (bbl/ft)}}