PTRE 461 Natural Gas Engineering
1. (20 points) If a natural gas has a specific gravity of 0.75 and contains 20% of H2S, 0% of N2, and 10% of CO2 (in molar percent), calculate its pseudo-critical pressure in psia and pseudo-critical temperature in ℉.
2. (30 points) For the following given data, estimate upstream pressure at choke:
Down stream pressure: 400 psia Choke size: 48 1/64 inch Flowline ID: 2 in Gas production rate: 14000 Mscf/d Gas specific gravity: 0.70 1 for air Gas specific heat ratio: 1.3 Upstream temperature: 120 ℉ Choke discharge coefficient: 1.05 Assuming gas viscosity is 0.02 cp and z-factor is 0.9.
3. (30 points) A 0.70 specific gravity natural gas flows from a 2-in pipe through a 1.0-in orifice-type choke. The discharge coefficient of choke is 1.03. The upstream pressure and temperature are 120 psia and 70 ℉, respectively. The down stream pressure is 90 psia (measured 2 ft from the nozzle). The gas specific heat ratio is 1.25. Assuming gas viscosity is 0.02 cp and z-factor is 0.9.
- What is the expected daily flow rate?
- Is icing a potential problem?
- What is the expected pressure at the nozzle outlet?
4. (20 points) A gas well produces 0.7 specific gravity natural gas. The average reservoir pressure is 2,800 psia. Reservoir temperature is 150 ℉. The well was tested at two flow rates:
Test point 1, flow rate: 1100 Mscf/d bottom hole pressure: 1700 psia Test point 2, flow rate: 1500 Mscf/d bottom hole pressure: 1000 psia
Use backpressure model with pressure squared approach to estimate the gas rate at a flowing bottomhole pressure of 800 psia.
