Lecture 3- Gas Engineering

7/29/2019 Lecture 3- Gas Engineering

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Lecture 3



Impact of Sour Gas & Non-hydrocarbon

components on compressibility factor:

•

Sour natural gases containing H2S and/or CO2 frequently exhibit different compressibility factorbehavior than do sweet natural gases.

• A calculation procedure to account for these

differences includes pseudo-critical temperatureadjustment factor which is a function of theconcentration of CO2 and H2S in the sour gas.

• This correction factor is then used to adjust thepseudo-critical temperature and pressureaccording to the following expressions.



ε = 120(A0.9 – A1.6) + 15(B0.5 – B4.0)

Where:

ε = adjustment factorA = sum of mole fractions of CO2 and H2S

B = mole fraction of H2S

The pseudo-critical temperature is modified toget the adjusted pseudo-critical temperature

T’pc = T pc - ε

Similarly the pseudo-critical pressure is adjusted as

P’pc = Ppc x T’pc / { Tpc +B(1-B) ε }



Problem:A natural gas mixture consists of the following

composition:

a). Calculate the apparent Mol.wt of gas, gas gravity, Pseudo-

critical temp and Pseudo-critical pressure

b). Calculate the compressibility factor for gas at 900 °F and

1200 psia.

Component Mole Fraction

CH4

C2H6

C3H8

N2

CO2

H2S



Exploration Of N.G

•

The methods used to discover natural gasreservoirs are essentially those used to

petroleum reservoirs.

•

to search for surface evidence of theunderground formations (capable of being

reservoirs)

•

seepages of gas emitted from underground.• The only way of being certain is to drill an

exploratory well



Methods used

• Geological Survey

• Seismic Survey

•

Magnetometers



Production Of N.G

Well Completion

– This process includes strengthening the well hole

(wellbore) with casing, evaluating the pressure and

temperature of the formation, and then installingthe proper equipment to ensure an efficient flow of

natural gas out of the well.



1. Conductor casing (20 to 50 ft long, installed to prevent

the top of the well from caving in and to help in the process of

circulating the drilling fluid up from the bottom of the well)

2. Surface casing (2,000 ft long, to protect freshwater

deposits near the surface of the well from being contaminated

by leaking hydrocarbons or saltwater from deeper

underground)

3. Intermediate casing (longest section of casing)

4. Liner string (used instead of intermediate casing and are

commonly run from the bottom of another type of casing to

the open well area.

5. Production casing (deepest section of casing in a well

provides a conduit from the surface of the well to the

petroleum producing formation





The Wellhead

This consists of the pieces of equipment mounted at the

opening of the well to regulate and monitor the extraction

of hydrocarbons from the underground formation.

The casing-head:

• consists of heavy fittings that provide a seal between the

casing and the surface

The Christmas tree:

• is the piece of equipment that fits atop the casing and

tubing heads, and contains tubes and valves that serve to

control the flow of hydrocarbons and other fluids out of

the well





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Lecture 3- Gas Engineering