Page 28 - Handbook Of Multiphase Flow Assurance

22 1. Introduction

TABLE 1.3 Examples of reference conditions
Temperature Pressure
Standard cubic foot of gas United 60 °F = 15.555 °C 14.73 psia = 1.002 atm = 101.560 kPa
States
Normal cubic meter of gas Europe 15 °C = 59 °F 1 atm = 101.325 kPa = 14.696 psia
Stock tank barrel 60 °F = 15.555 °C 1 atm = 14.696 psia = 0.101325 MPa
Stock tank conditions for oil in United States: 14.696 psia = 1 atm, and 60 °F = 15.555 °C.
Standard conditions for gas in Russia: 101.325 kPa = 1 atm and 20 °C = 68 °F.
Normal conditions for gas: 760 mm mercury = 1 atm and 0 °C.
US standard conditions: 1 bar = 100 kPa = 0.1 MPa and 15 °C = 59 °F.
Standard conditions NIST, United States, 101.325 kPa = 1 atm and 20 °C.
Standard conditions GOST, Russia: 760 mm mercury = 101.325 kPa and 25 °C.

bathymetry, fluid behavior and environment parameters. However, analogs may differ sig-
nificantly from the target reservoir.

Units for fluid characterization
Reference conditions for measurement of hydrocarbon properties vary regionally. It is im-
portant to define which system of units will be used in a project. Standard conditions even
vary for defining the linked units such as quantities of gas and oil used in the gas oil ratio
(GOR). Gas is measured in standard cubic feet, standard cubic meters or in normal cubic
meters. However, gas is sold by its heating value because different compositions provide
different amounts of heat when combusted
Oil can be measured and is sold by stock tank barrels, cubic meters or metric tons, with
various quality oils getting different market price. The “standard” conditions at which fluid
quantities are defined vary for liquid and for gas. Measurement of liquids by mass usually
yields the least error compared to measurement by volume. Several examples are shown be-
low in Table 1.3.
An engineer has to verify in any PVT-related fluid analysis work that the units used to
describe fluid properties match those used in the project. The reference conditions should be
defined in the Basis of Design. Mass definition of a metric ton does not vary with temperature
or pressure. The variability of the volume metrics leads to sale contracts for natural gas using
caloric or heating value of the gas obtained upon its combustion.

Introduction to flow assurance risk analysis

A flow assurance specialist's objective is to make sure that a project is designed for safe and
reliable operation in relation to flow assurance issues and that all “boxes are checked.” For
that, we first must define what those boxes are because if we can measure, we can improve.
Flow assurance becomes an analysis of thermal, hydraulic and fluid-related threats to flow
and fluid quality and mitigation of these threats with equipment, chemistry and procedure.
This analysis lends itself well to a “bowtie” risk analysis (Fig. 1.15).