Page 141 - Well Logging and Formation Evaluation

Equity Determinations 131

• GBV: from the height of the total hydrocarbon-bearing column
• NPV: from the sum of the net footage times the porosity
• HCPV 1: from the sum of the net footage times the porosity times
(1 - S w), S w derived by Archie
• BOE 1: as per HCPV 1 but multiplying any gas footage by the gas factor
before summing
• HCPV 2: as per HCPV 1 except using the J function instead of Archie
• BOE 2: as per HCPV 2 but multiplying any gas footage by the gas factor
before summing

Let the well on your side of the boundary be denoted by A, and the one
on the other side by B. Determine the following parameters:

( ))
EQ GBV) = GBV A) ( GBV A) + GBV B ,
(
(
(
where GBV(A) is the GBV proxy determined from well A, etc.
EQ NPV) = NPV A) ( NPV A) + NPV B))
(
(
(
(
EQ HCPV 1 = HCPV A) ( HCPV A) + HCPV B))
)
(
(
(
(
1
1
1
)
EQ BOE 1 = BOE A) ( BOE A) + BOE B))
(
(
(
(
1
1
1
EQ HCPV 2 = HCPV A) ( HCPV A) + HCPV B))
)
(
(
(
(
2
2
2
EQ BOE 2 = BOE A) ( BOE A) + BOE B)).
)
(
(
(
(
2
2
2
Note that if it has been decided to use more than one well on either side
of the boundary, the equations can easily be extended, using relative
weighting factors as appropriate. For example, if two wells are chosen for
your side (A and B) but only one is available from the other side (C), and
you feel that well A is likely to be twice as important as well B, you could
calculate:
)
())
()
(
EQ BOE 1 = ( BOE A + 05.* BOE B
1
1
()).
()
( BOE A + 05.* BOE B + BOE C
()
1
1
1
We are not interested in the absolute value of EQ(BOE 1), only its rel-
ative size compared with other proxies for equity (e.g., EQ(BOE 2)) and
how it varies subject to input petrophysical parameters. Which of these is