Page 292 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Secondary Recovery 259

Depletim Early
stage +New -%?- Younq +Mature 4) sect. 5

-----
bModel studies ----
JcPerformoncr Materiol bolonee
Pressure-curnulolive

1
Possible
Sect. 2
Reserve f=/\] ~Mderote
clossification Proved LDW

S
- Production history
-
3 Sect.1
L
.-
I
0 2 3
TIME
Figure 5-147. Quality of reserves [274].

production from completion to depletion. Section 3 shows the range of possible
reserve estimates through the life of the property. Section 4 shows at what stage
of the life of the property each method of reserve estimate method becomes
available. The solid line indicates for what period each method is most appli-
cable. Section 5 names the depletion stage of the reservoir.
The quality of reserve estimates throughout the industry should improve now
that the SPE definitions for proved reserves are being accepted. When the
definitions for probable and possible reserves are approved, uniform factors for
risk analysis can be made [275].
SECONDARY RECOVERY

Definitions
Secondary and Tertlary Recovery

Primary recovery, as already discussed, refers to the recovery of oil and/or
gas that is recovered by either natural flow or artificial lift through a single
wellbore. Thus, primary recovery occurs as a result of the energy initially present
in the reservoir at the time of discovery. When the initial energy has been
depleted and the rate of oil recovery declines, oil production can be increased
by the injection of secondary energy into the reservoir. Secondary recovery is
the recovery of oil and/or gas that involves the introduction of artificial energy