Petroleum Production Engineering Fundamentals

Introduction

This short article will provide basic information about petroleum production engineering and the process that have been involved. Complete oil and gas production system consists of reservoir, well, flow line, separators pump and transportation pipeline. Figure below will clearly shows the process of the petroleum production from reservoir to the transportation pipeline.

The reservoir supplies well bore with crude oil or gas, the well will provide a path to the production fluid to flow from the bottom hole to surface and offers a means to control the fluid production rate, and the flow line leads the produced fluid to separators. The separators will separate the water and gas from the crude oil. Pumps and compressors will use to transport oil and gas through pipeline to the shore for refinery.

AGA 7 Calculation

AGA 7 takes a flowing volume, rate or flowing conditions and calculates base volume, base volume flow rate or volume correction factor. It requires flowing and base pressure, temperature and compressibility. Compressibility is calculated by your favourite equation of state, such as AGA 8.The algorithm for the calculation is extremely straightforward. It is really just the application of the real gas law to the measured volume.

For Flowing Volume:

Pf * Vf = Zf * n * R * Tf

so Vf = Zf * n * R * Tf / Pf

For Base Volume:

Pb * Vb = Zb * n * R * Tb
so Vb = Zb * n * R * Tb / Pb

Dividing the equations, we get

Vb/Vf = (Zb * n * R * Tb / Pb )/( Zf * n * R * Tf / Pf)
so Vb= Vf *(Zb * n * R * Tb * Pf) / ( Zf * n * R * Tf * Pb)

Changing the pressure and temperature doesn't change the number of moles, and R is a constant, so:

Vb= Vf *(Zb * Tb * Pf) / ( Zf * Tf * Pb)

S is defined as Zb / Zf
Fpm is defined as Pf / 101.56 kPa, or Pf / 14.73 PSIF
pb is defined as 101.56 kPa / Pb, or 14.73 PSI / Pb
Ftm is defined as 288.7056 Deg Kelvin / Tf, or 519.67 Deg. Rankin / Tf
Ftb is defined as Tb / 288.7056 Deg Kelvin, or Tb / 519.67 Deg. Rankin


So Fpm * Fpb = Pf / Pb
and Ftm * Ftb = Tb / Tf
So Vb = Vf * Fpm * Fpb* Ftm * Ftb * S

Calculate Fpm = Pf / 101.56 kPa (US base conditions, defined by AGA 7 spec)
Calculate Fpb = 101.56/Pb
Calculate Ftm = (15.55556 + 273.15)/Tf Deg. K (US base conditions, defined by AGA 7 spec)
Calculate Ftb = Tb / (15.55556 + 273.15) Deg. K (US base conditions, defined by AGA 7 spec)
Calculate S = Zb / Zf = Fpv2
Calculate BMV (base multiplier value) = Fpm * Fpb * Ftm * Ftb * S

Apply meter factor to BMV (Note: this is often done to the actual volume prior to using AGA 7.)

Calculate base volume Vb = Vf * BMV / 1000 (Converts M3 to E3M3, or Ft3 to MSCF)

Source: http://www.squinch.org/