Page 20 - PVT Property Correlations

Chapter 1

Introduction

The accuracy of many petroleum engineering calculations (e.g., material bal-
ance calculations, reserves estimation, well test analysis, advanced produc-
tion data analysis, nodal analysis, surface network modeling, surface
separation, and numerical reservoir simulations) largely depends on the accu-
racy of pressure, volume, and temperature (PVT) data. In an ideal situation,
PVT data are determined from laboratory experiments performed on repre-
sentative fluid samples collected from wellhead, surface separators, or well-
bore. PVT reports give the results of PVT experiments usually conducted at
reservoir temperature. Other routine measurements are usually taken as part
of monitoring programs in oil- and gas-field operations. These include fre-
quent measurement of API gravity of stock-tank oil, dead oil viscosity at
atmospheric temperature or at different temperatures, specific gravity of sep-
arator gas, and composition of separator gas. In some cases, bubble point
and dew point pressure can be estimated from production data. In addition,
downhole density of reservoir fluids can be estimated from measurements of
pressure versus depth (repeat formation tester measurements, RFT).
Common hydrocarbon PVT properties that appear in many calculations
in reservoir and production engineering include saturation pressure (bubble
point pressure for oils and dew point pressure for gases); solution gas oil
ratio; vaporized oil gas ratio; formation volume factors for oil and gas; oil
and gas density; oil and gas viscosity; single- and two-phase z-factor for
gases; and oil and gas isothermal compressibility. The generation of repre-
sentative values for these properties is the focus of this book.
Other PVT properties that are used in specific applications are reviewed
in other texts (McCain, 1990; Whitson and Brule, 2000; Ahmed, 2016;
Caroll, 2009; Mullins et al., 2007). These include water PVT properties, sur-
face tension, minimum miscibility pressure, K values, hydrate formation
pressure and temperature, asphaltene onset pressure and temperature, and
wax appearance temperature.

IMPORTANCE OF ACCURATE PVT PROPERTIES
PVT properties are required for most reservoir, production, and surface-
processing calculations. Inaccurate estimation of PVT properties can lead to
significant errors in calculation results. Spivey and Pursell (1998) studied the

PVT Property Correlations. DOI: https://doi.org/10.1016/B978-0-12-812572-4.00001-1
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