A Lease Automatic Custody Transfers unit is a piece of oil field equipment that is intended to accurately measure oil when it changes custody from one company to another. It can be used to calculate royalties or act as a 'cash register' between a company selling the oil and a company buying the oil.
- Abbreviated as LACT
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Each LACT Unit is different and is typically designed for each application depending on process conditions, gravities and individual companies' specifications and shipping method. However, certain components are common in all LACT units. From inlet to outlet, the components are listed below.
A cut probe or oil water detector determines the amount of water in the line. Depending on the specification of the customer, the amount of water may vary from 1 to 5 percent water. Before the oil enters the cut probe, it goes through a static mixer to ensure a homogeneous mixture.
Downstream of the cut probe, a reject valve determines where the oil goes. Should the amount of water exceed the predetermined specification, the valve will divert the flow and not allow the fluid to pass through the meter. From here, the oil may enter a reject tank or back into the LACT tank for further treatment.
Prior to metering, the oil must be sampled to determine the meter factor. An isokinetic sampler takes sample of the production stream. Prior to sampling, the oil is again mixed to ensure a homogeneous mixture. After sampling, the oil is stored in a sample container where the cut is read to determine the average cut during metering.
After the cut passes through the reject valve, it then goes through the meter. There are two different types of meters curently in use. They are a positive displacement or Coriolis Meter.