Reservoir simulator benchmark tests

Brief

Before running any 3D reservoir simulator for a full scale field history matching or forecasts it is a good practice to make sure that the simulator is performing well on a simple benchmark tests with the well known analytical solutions.

By running those cases you could get ahead of the learning curve and gain confidence in your simulation results.

Calculating well potential

Analytical equations are available to calculate the flow rate potential for unstimulated and stimulated wells. Steady state and pseudo steady state flow regimes are considered.

Simulation Test Runs

1. Vertical well in a square drainage area pseudo steady state flow
2. Vertical well in a square drainage area steady state flow
3. Fracture vertical well in a square drainage area pseudo steady state flow
4. Fractured vertical well in a square drainage area steady state flow
5. Horizontal well in a square drainage area pseudo steady state flow
6. Horizontal well in a square drainage area steady state flow
7. Horizontal well with orthogonal fractures in a rectangular drainage area pseudo steady state flow
8. Horizontal well with orthogonal fractures in a rectangular drainage area steady state flow

Gas Recovery

12% more recovery with the enhanced production over 20 years. Why?

Because of the pressure! The lower the reservoir pressure the more gas is produced before the water hits the perfs. It’s just physics!

Math and Physics

According to the Boyle's law (1662):

$PV = constant$

where P is pressure, V is volume.

In our case

$PV = constant = P_1V_1 = P_2V_2=P_{res}V_{res}$

The gas produced volume of the "Slow case"

$V_1 = \frac{P_{res}V_{res}}{P_1}$

The gas produced volume of the "Fast case"

$V_2 = \frac{P_{res}V_{res}}{P_2}$

And V₂ > V₁ because P₂ < P₁. The lower the P₂ gets over P₁ the higher the incremental recovery will be.

Summary

Produce gas reservoirs fast to increases recoveries.

If you have an aquifer you have to produce fast.

If you don’t have an aquifer…, so you don’t have water to complain.

Video

Watch our video explaining the gas reservoir production using the Can Of Beans (Gas) as an example

Model overview

• Cylindrical grid (10x10x30)
• re=500m, rw=0.1m, h=30m
• kx=ky=5mD, kz/kx=0.1, phi=0.2
• Pi=300bar, hres=3000m
• Gas and water PVT model
• SGgas=0.58
• Aquifer at the bottom (CT infinite extent)
• qgas_slow = 100 000 m3/d
• qgas_fast = 200 000 m3/d

3D reservoir simulation software

• ECLIPSE
• tNavigator
• CMG
• Waiwera

See also

• Petroleum Engineering
• Hydraulic fracturing
• 29+ reasons why you can not increase the production

References

By Mikhail Tuzovskiy on 20230807172714