Practical Concerns In Metering Fluids From Production Operations
Authors: Templeton W.J. 
Published: December 2007

Accurate measurement of oil and gas is of vital concern. Measurement of these vapor and liquid streams by mass, volumetric, and energy techniques are reviewed to better provide an understanding of the type of measurement recommended for use in each case. Improved accuracy in primary measuring devices, auxiliary equipment, and sampling are reviewed from a practical aspect, whereby measurement accuracy and ultimately dollars can be realized. The accuracy obtained in measurement directly affects the cash register and the bottom line of your financial sheet. The practical concerns presented in the metering of fluids will improve the accuracy of your oil and gas measurement.

Introduction

As producers, there are two principal products that we are interested in measuring, namely, oil and gas. Along with the principal products that are measured are contaminants that we do not want to buy-such as water, BS, carbon dioxide, hydrogen sulfide, nitrogen, oxygen, and water vapor. It is necessary to measure the contaminants so that we do not buy them, but deduct the contaminant volume from the total measurement.

Subjects covered in this presentation will be the types of measurement determinations used in production operations, such as (1) volumetric, (2) mass, and (3) energy. With each type of measurement, the practical aspects of the primary measuring devices practical aspects of the primary measuring devices such as orifice, positive displacement, turbine, static, pressure and temperature recorders, and auxiliary equipment such as samplers, calorimeters, densitometers, and contaminant measurement will be reviewed.

PRACTICAL CONCERNS IN METERING PRACTICAL CONCERNS IN METERING What are the three types of measurement and when and how are they used?

Volumetric Measurement

Volumetric measurement is the method of determining a volume of either a liquid or gas and giving the units of measurement in define quantities at standard conditions such as cubic feet, gallons, or barrels, or corresponding metric units. Volumetric measurement is used when the physical properties of the fluid being measured are known and, properties of the fluid being measured are known and, therefore, the volumes being measured can be corrected to standard conditions. Physical properties referred to are the coefficient of expansion properties referred to are the coefficient of expansion and compressibility of liquids and super compressibility of gases.

Volumetric measurement is performed by general industry meters, such as orifice, positive displacement, and turbine meters. The equations for determining volumes are as follows.

Gas Measurement by Orifice

Q =

. . . . . . . . . . . . . . . . . . . . . . (1)

where Q = quantity rate of flow at base conditions, cu ft/hour Fb = basic orifice factorhw = differential pressure across the orifice, inches water Pf = absolute static pressure, psia

Other factors are explained in Ref. 1.

Turbine or PD Meters for Gas Measurement

Q = (Dial Diff) (C) (C) (MF),............(2)t p

where

Q = quantity of flow at base conditions Dial Diff = difference between ending and beginning meter dial readings Ct = correction for temperature to correct volume readings to standard conditions

C = 460 + 60 Ft 460 + (Flowing Temp degrees F)