1. Gathering Oil From the Fields
Book 1: Chapter 2
Gathering Oil From the Fields

2. Objectives
After reading the chapter and reviewing the materials presented the students will be able to:
Understand flow lines and lease tanks
Identify gauging and testing methods
Describe lease automatic custody transfer
Explain meter proving

3. Flow Lines and Lease Tanks
An oil field may have several hundred wells, with flow lines that carry crude oil from the wells to the lease tanks.
Sometimes, the crude oil from the leases is transported away via pipelines without the use of lease tanks. In this case, automatic equipment is used in lieu of tanks for continuous measurement and sampling of the crude oil volumes transported away via pipeline.
A flow line connects the wellhead to the oil and gas separators.
From the separators, the gas is taken from the top connection to the gas system, with oil leaving through the bottom line.
If further treatment is required to remove water, heat and chemicals are used in the heater-treaters.
A tank battery may be installed by the producer for the temporary storage of crude oil.
Before being run to the pipeline, the oil is gauged (measured), the specific gravity is determined, and the amount of basic sediment and water (BS&W) content is determined.

4. Gauging and Testing
A newer method called lease automatic custody transfer (LACT), renders tanks unnecessary for gauging and checking the oil.
Conventional Method: In the conventional method, the depth of oil received in the tank is measured using a gauging tape, a metal measuring tape attached to a plumb bob and held in a frame equipped with a handle and a winding crank. The tank measurement is converted to barrels.
To check the specific gravity and BS&W content, the tank is sampled with a “thief” at two or three different levels in the tank so that a composite sample is collected that will be representative of the whole tank.
A combination hydrometer-thermometer, called thermohydrometer is used to determine the API gravity at 600 F. The price paid for the crude oil is determined in part by the API gravity at 600 F.
A centrifuge is used to separate the BS&W in the sample from the oil. The water and sediment are forced to the bottom of the centrifuge tube.
Before the outlet valve is opened to run the oil in the pipeline gathering system, the tank is gauged and the amount of oil is recorded on the run ticket. After the oil is run the closing gauge is taken. Subtracting the closing gauge volume from the opening gauge volume gives the volume of oil run from the tank. All these data are entered on the run ticket, which is then signed by both parties.

5. Lease Automatic Custody Transfer (LACT)
Automated equipment has been devised to:
Measure by meter and record the volume of oil.
Detect the presence of water in the crude oil stream and indicate the percentage.
In the case of excessive water, divert the flow into special storage to be held for treatment.
Determine and record the temperature of the oil.
Automatically correct the measured volume to standard temperature (600 F).
Determine and make a record of API specific gravity of oil transferred.
Switch well production from a full tank to an empty one and run the oil from the full tank to the pipeline gathering system.
In case of malfunction, shut in the wells and relay an alarm to a remote point.

6. Meter Proving
The station operator can prove the meter while sitting at a console in the control room.
The panel contains three counters that total the number of barrels of flow through the station’s three working meters.
The count by the meter and the prover indicator are observed. Then a simple calculation establishes the meter factor to be used as a multiplier to produce accurate quantities.

7. Summary
An oil field may have several hundred wells, with flow lines that carry crude oil from the wells to the lease tanks.
A flow line connects the wellhead to the oil and gas separators.
From the separators, the gas is taken from the top connection to the gas system, with oil leaving through the bottom line.
If further treatment is required to remove water, heat and chemicals are used in the heater-treaters.
A tank battery may be installed by the producer for the temporary storage of crude oil.
Before being run to the pipeline, the oil is gauged (measured), the specific gravity is determined, and the amount of basic sediment and water (BS&W) content is determined.
A newer method called lease automatic custody transfer (LACT), renders tanks unnecessary for gauging and checking the oil.
To check the specific gravity and BS&W content, the tank is sampled with a “thief”.
A combination hydrometer-thermometer, called thermohydrometer is used to determine the API gravity at 600 F.
A centrifuge is used to separate the BS&W in the sample from the oil. The water and sediment are forced to the bottom of the centrifuge tube.
Before the outlet valve is opened to run the oil in the pipeline gathering system, the tank is gauged and the amount of oil is recorded on the run ticket. After the oil is run the closing gauge is taken. Subtracting the closing gauge volume from the opening gauge volume gives the volume of oil run from the tank. All these data are entered on the run ticket, which is then signed by both parties.
The count by the meter and the prover indicator are observed. Then a simple calculation establishes the meter factor to be used.

8. Home Work 1. What is used to remove water from crude oil?
2. What is used for the temporary storage of crude oil?
3. What new method renders tanks unnecessary for gauging and checking the oil?