Total produced or injected flowrate of all fluids across the well-reservoir contact with the volumes measured at the sandface temperature and pressure conditions.

Usually abbreviated as or .

The concept applies both to producing and injecting wells.

The main purpose of describing the intakes and offtakes in terms of the Total sandface flowrate is that it measures the actual flowing volumes in porous formations and as such directly relate to reservoir pressure.

For volatile oil fluid model the total sandface flowrate is related to surface flowrates of fluid components as:

q_t = q_w + q_o + q_g = B_w \, q_W + (B_o - R_s \, B_g) \, q_O + (B_g - R_v \, B_o) \, q_G

where

	water, oil and gas sandface flowrates
	water, crude oil and natural gas surface flowrates
	formation volume factors between separator and sandface pressure/temperature conditions
	Solution GOR and Vaporized oil ratio at sandface pressure/temperature conditions

It is related to Liquid production rate as:

q_t = \Big[ B_w Y_w + \big[ (B_o - R_s B_g) + (B_g - R_v B_o) \cdot GOR \big] \cdot (1-Y_w) \Big] \cdot q_L

where

	Production Water Cut
	Production Gas-Oil-Ratio

Starting with definition of Total sandface flowrate and substituting the expression of Oil surface flowrate, Gas surface flowrate, Water surface flowrate through Liquid production rate one arrives to .

It simplifies for the Black Oil model to:

q_t = B_w \, q_W + (B_o - R_s \, B_g) \, q_O + B_g  \, q_G = B_w \, q_W + B_o \, q_O + B_g ( q_G - R_s \, q_O ) = B_w \, q_W + \left( 1 + \left( \frac{GOR}{R_s} -1 \right) \cdot  \frac{R_s \, B_g}{B_o} \right) \cdot B_o\, q_O

or

q_t = B_w \, q_W + \left( 1 + \left( \frac{GOR}{R_s} -1 \right) \cdot  \frac{R_s \, B_g}{B_o} \right) \cdot B_o\, q_O = 
\left[
B_w \, Y_W + \left( 1 + \left( \frac{GOR}{R_s} -1 \right) \cdot  \frac{R_s \, B_g}{B_o} \right) \cdot B_o\, (1- Y_w)
\right] \cdot q_L

It simplifies further down to production from undersaturated reservoir as:

q_t = B_w \, q_W + B_o \, q_O = \left[ B_w Y_w + B_o (1- Y_w) \right] q_L

and even simpler for single-phase fluid (water, dead oil or dry gas) with surface flow rate and formation volume factor B as below:

q_t = q \cdot B

See Also