Lecture 2: Overview and Field Operations - Natural Gas Processing

A set of QUESTION_AND_ANSWER flashcards covering key concepts from Lecture 2 on natural gas sources, processing objectives, field operations, hydrate prevention, separators, dehydration, pigging, and flow regimes.

What are the two main sources of natural gas?

Associated (gas+oil) gas and non-associated gas.

What classifications describe natural gas compositions?

Lean vs. rich gas; sweet vs. sour (H2S/CO2 present).

Name common product types from natural gas processing.

Natural gas (sales gas), LNG, LPG, and NGL.

Which specifications are typically specified for natural gas?

Water content, combustion characteristics, heating value, Wobbe number, hydrocarbon dew point, cricondentherm, and RVP.

List typical purposes of gas processing plants.

Dehydration to meet specs, oil stabilization (H2S removal), helium recovery, and liquefaction for LNG or storage.

How do gas plants optimize profits related to liquids recovery?

By adjusting the fraction of liquids recovered while meeting the sales gas specifications.

Why is dehydration performed before cryogenic processing?

To prevent hydrate formation in downstream cryogenic equipment.

What is the role of MEG in hydrate prevention?

Monoethylene glycol (MEG) or methanol (MeOH) is injected at the wellhead to prevent hydrate formation.

What does GOSP stand for and what is its purpose?

Gas-Oil Separation Process; field separation to remove liquids from gas, often in stages with separators and mist extraction.

Name the three main mechanisms used in gas-oil separation (GOSP).

Momentum, gravity, and coalescence.

What are the key components of a gravity separator in GOSP?

Inlet diverter, gas separation section, liquid separation section, and mist extractor; vertical or horizontal configurations.

What is the function of a mist extractor?

Capture entrained droplets in the gas outlet to reduce liquid carryover.

What is the purpose of dehydration using a TEG contactor?

Remove water from gas to prevent hydrates and to meet the gas dew point specification.

How is glycol regenerated in a glycol dehydration system?

Wet rich glycol is regenerated in a regenerator (fractionator + reboiler) to produce dry glycol for reuse.

Why is hydrate prevention necessary in field processing?

Hydrates can plug pipelines and damage equipment; inhibitors (MeOH/MEG) are used to prevent formation.

What is the purpose of field pigging?

To clean pipelines, remove debris, calibrate flow meters, and facilitate maintenance and inspection.

Name the seven principal two-phase flow regimes in horizontal pipes.

Bubble flow, plug flow, stratified flow, stratified-wavy flow, slug flow, annular flow, spray flow.

What flow regimes are common in vertical pipes?

Bubble flow, slug flow, churn/froth flow, annular flow, and mist flow.

What is cricondentherm in hydrocarbon systems?

The maximum temperature at which two phases can exist in the hydrocarbon system (hydrocarbon dew point related concept).

What are three options if cricondentherm > LET (Lowest Expected Temperature) in pipeline design?

Two-phase pipeline flow; condensate/NGL removal; or dense-phase transport.

What are three typical objectives in processing for gas transport and condensate handling?

1) Produce a transportable gas stream; 2) Produce a saleable gas stream; 3) Maximise condensate production.

What is the Joule–Thomson (JT) effect in gas expansion?

Change in temperature when a gas expands (throttling) at constant enthalpy; the sign depends on the inversion point and gas composition.

What is the JT inversion point for methane around 100°C?

Approximately 500 atm (about 7350 psia); above this, expansion heats the gas, below it cools. mu changes sign.

What problems can hydrates cause in pipelines if not controlled?

Plugging, damage to piping, and hazardous conditions if hydrates are heated or ignited.

Which component’s content is a major factor in hydrate formation?

Propane content significantly influences hydrate formation conditions.

What is a three-phase gravity separator intended to separate?

Gas, liquid hydrocarbon, and glycol/water (glycol-containing phase) in the presence of dehydration.

What is the purpose of a glycol absorber unit schematic?

To remove water from gas by contacting with glycol; regenerated glycol is recycled to absorber.