Difference between revisions of "Gas Flowing Material Balance"

Revision as of 08:39, 11 December 2017

Brief

Gas Flowing Material Balance is the advanced engineering technique to determine the Reservoirs GIIP and recovery as well as Well's EUR and JD.

Gas Flowing Material Balance is applied on the Well level given readily available well flowing data: production rate and tubing head pressure.

The interpretation technique is fitting the data points with the straight line to estimate GIIP and JD.

Math & Physics

Combining the gas pseudo state flow equation and the Gas Material Balance equation to get Gas Flowing Material Balance equation:

P_{\bar{P}}= P_{P_{wf}} + q_g b_{pss}

^[1]

where

b_{pss} = \frac{1422 \times 10^3\ T_R}{kh\ J_D}

Material balance pseudo-time:

t_{ca} = \frac{\mu_{gi} c_{gi}}{q_g}\int\limits_{0}^{t}\frac{q_g}{\bar{\mu_g} \bar{c_g}}dt

Discussion

well vs reservoir

Workflow

Calculate the red line:
1. Given the GIIP
2. Calculate $\frac{P}{z}=\frac{P_i}{z_i} \left (1- \frac{G_p}{GIIP}\right )$
Calculate the orange curve:
1. Given the flowing wellhead pressures, calculate the flowing bottomhole pressures, $P_{wf}$
2. Convert the flowing pressures to pseudopressures, $P_{P_{wf}}$
3. Given the JD, calculate the $b_{pss}$
4. Calculate the pseudopressure, $P_{\bar{P}}$
5. Convert the pseudopressure to pressure, $\bar{P}$
6. Calculate the $\frac{\bar{P}}{z}$
Calculate the gray JD curve:
1. Calculate the gas productivity index, $J=\frac{q_g}{P_{\bar{P}}-P_{P_{wf}}}$
2. Calculate the JD, $J_D=\frac{1422 \times 10^3\ T_R}{kh} J$
Change the red line to match the orange curve
1. Change the GIIP
2. Change the $\frac{P}{z}$
Change the flat JD gray line to match the changing JD gray line
Save the Gas Flowing Material Balance model
Move to the next well

bsss

Calculate initial pseudopressure, $P_{Pi}$ Calculate material balance pseudo-time, $t_{ca}$ Plot $\frac{P_{P_i}-P_{P_{wf}}}{q}$ versus $t_{ca}$ . The intercept gives $b_{pss}$ and $J_D$ . Calculate the average reservoir pseudopressure from Gas Flowing Material Balance equation, $P_{\bar{P}}$