Page 187 - Hydrocarbon

174 Deterministic Methods

and since measured prior to any production having taken place it was the volume
initially in place.
GIIP is the equivalent expression for gas initially in place.
HCIIP is the hydrocarbons initially in place – a general term covering STOIIP
and GIIP.
Ultimate recovery (UR) and reserves are linked to the volumes initially in place
by the RF, or fraction of the in-place volume which will be produced. Before
production starts, reserves and UR are the same.
GRV is the gross rock volume of the hydrocarbon-bearing interval and is the
product of the area (A) containing hydrocarbons and the interval thickness (H ),
hence
3
3
GRV ¼ AH ðft Þ or ðacre ftÞ or ðm Þ
The area can be measured from a map. Figure 7.1 clarifies some of the reservoir
definitions used in reserves estimation:
H is the isochore thickness of the total interval (gross thickness), regardless of
lithology

Net sand is the height of the lithologic column with reservoir quality, that is the
column that can potentially store hydrocarbons
Net oil sand (NOS) is the length of the net sand column that is oil bearing

The other parameters used in the calculation of STOIIP and GIIP have been
discussed in Section 6.4, Chapter 6. The formation volume factors (B o and B g ) were
introduced in Section 6.2, Chapter 6. We can therefore proceed to the ‘quick and

well 1 well 2

net sand
net oil sand
OWC
H = gross interval
thickness
GR
Res

H GR Res
OWC

H

Figure 7.1 De¢nitions used for volumetric estimates.