PTRE461 Natural Gas Engineering Question

PTRE 461 Natural Gas Engineering

Mid-Term Exam

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 oF.

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 oF, respectively. The downstream 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.

a) What is the expected daily flow rate?

b) Is icing a potential problem?

c) 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 F. 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.