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NTL 92-4

Notice to Lessees and Operators of Onshore Federal and Indian
Oil and Gas Leases Within the Jurisdiction
of the New Mexico State Office
(NTL 92-4 New Mexico)

Non-Mechanical Temperature/Gravity Compensation on Lease Automatic Custody Transfer (LACT) Units

I. Background.

Onshore Oil & Gas Order No.4 (Order No.4) established minimum standards for oil measurement. The Order requires that all LACT units be equipped with an "automatic temperature\gravity compensator." These compensators mechanically correct the metered volume for changes in temperature from 60 degrees F. and are set for a range of oil gravities.

Operators have installed electronic temperature averagers (ETA's) on LACT units believing they were in compliance with the Order. The ETA's are not automatic temperature/gravity compensators in the pure sense. The metered volume is mathematically corrected for temperature changes rather than mechanically. However, the result is the same.

II. Purpose: Establish standards for the approved use of ETA's.

III. Authority: Title 43 CFR part 3162.7-1

IV. Definitions:

CTL means the API factor used to correct oil volume for the effect of temperature.

Round trip or Run means the volume displacement of the ball moving in both direction of a bi-directional prover or the preset volume measured by a master meter.

V. Equipment Requirements:

A. Accuracy minimum specifications:

  • Record temperature once per bbl.
  • Temperature probe accuracy, +/- 0.5 degree F. over operating range.
  • Record counts of data points, +/- 1% of input counts
  • Average temperature recorded, nearest 0.1 degrees F.

B. Fail-safe minimum features:

  • Retain data collected for 35 days or sales period whichever is greater in the event power loss.
  • LACT Shut-down in the event of computer or meter failure
  • LACT Shut-down in the event of ATC power failure

VI. Proving Requirements:

The proving requirements are the same for ETA as for ATC/ATG compensated LACT outlined in order No. 4, except as specified below.

A. The flowing temperature of the meter and prover must be recorded for each round trip (run) on the proving sheet. However, the CTL factor need not be used in the meter factor calculation if the prover and meter temperature difference is within +/- 0.5 degree F. The CTL factor must be used, if the prover and meter have greater than +/- 0.5 degree F. difference.

B. The temperature recorder must be tested for accuracy at operating temperature during each proving. The temperature recorder must be tested annually at the following three points:

  • Lowest operating temperature or ice bath
  • Operating temperature
  • Highest operating temperature

A certified thermometer is to be used for both tests. If the temperature recorder is in error by more than +/- 0.5 degrees, the ETA must be repaired or recalibrated and a meter adjustment made.

VII. Data Retention:

In addition to the standard sales data, the following information must be retained for a period of 6 years and supplied to the authorized officer upon request. The data may be retained on electronic or paper medium.

A. Sales information:

  • Dates and times of data points
  • Sums of data points
  • Counts of data points
  • API gravity and BS&W
  • Beginning and ending meter readings
  • Beginning and ending dates and times

B. Proving Information:

  • Calibration report
  • Meter Adjustment reports


All equipment in place on the date of this NTL must meet the standards of this notice.

APPROVED:Date: 12-24-91Larry L. Woodard
New Mexico State Director