Page 79 - Introduction to Petroleum Engineering

APPLICATIONS OF FLUID PROPERTIES 63

Reduce Remove All gas Reduce
pressure gas out pressure

Gas
Gas Gas
V A = V sat Oil V B < V sat Oil V B < V sat Oil

V B < V sat Oil
Piston V E < V B < V sat Oil

Step A Step B Step C Step D Step E
P A = P sat P B < P sat P B < P sat P B < P sat P E < P B < P sat
FIGURE 3.9 Differential liberation.

Gas (1) Gas (2) Stock tank gas

Input
stream First stage Second stage Third stage
P 1 , T 1
P 2 , T 2 P ST , T ST

Liquid (1) Liquid (2)
Stock tank oil

FIGURE 3.10 Multistage flash.

3.8 APPLICATIONS OF FLUID PROPERTIES

Petroleum engineers use fluid properties in a variety of applications, including
volumetric estimation of oil and gas in place, material balances, well testing, and
reservoir modeling. For volumetric estimates, they use FVF. For material balances,
they use a combination of FVF, GOR, and fluid compressibilities. For well testing
and reservoir modeling, they use fluid viscosities in addition to the fluid properties
needed for the other applications.
Over the past 40 or 50 years, engineers have developed software for modeling of
reservoirs with the five types of hydrocarbon fluids described previously. These
models predict changes in reservoir pressures as fluids are produced from or injected
to the wells. Model predictions are compared to field observations, yielding insight
to guide future operations.