Porosity and Permeability in Bioturbated Sediments - Trace Fossils as Indicators of Sedimentary Environments - page 826

10

A

B

1

0.1

1 cm

Arithmetic mean

Geometric mean
Harmonic mean

0.01

0 0.1 0.2 0.3 0.4

% Bioturbation

0.5 0.6 0.7 0.8 0.9 1

FIGURE 10 The predictable permeability relationships that may be present in bioturbated flow
media (Lysing Formation, Norway). (A) Graph showing three possible solutions to estimating
the bulk permeability (geometric, arithmetic, and harmonic means). The red star indicates the actual
bulk permeability of a sampled plug (B), which is plotted according to its degree of bioturbation and
measured permeability. Here, it appears that the burrows are conforming most closely to the har-
monic mean, suggesting that, in spite of the high levels of bioturbation, some flow complexities
are present.

bioturbation. As with most other biogenic flow media, the resulting flow
network is an overall intricate, locally interconnected horizontal and vertical
burrow system. In this example, bulk-permeability measurements also show
that k h is higher than k v ( Fig. 10 ) and that permeability distributions are aniso-
tropic. This is likely the result of increased horizontal burrowing associated
with shelfal trace-fossil assemblages or may be related to the small
(2.54 cm) scale of the permeability measurement.

4.3.2.2 Terang-Sirasun (Miocene), East Java Sea
Pemberton and Gingras (2005) provided an example of non-SCD from the
Terang-Sirasun gas field of the East Java Sea. Terang-Sirasun resides in the
Kangean block approximately 140 km north of Bali ( Matzke et al., 1992 ).
The field comprises reserves residing in the Lower Paciran Sandstone Member
(Late Miocene), the Upper Paciran Sandstone Member (Late Miocene), and the
Paciran Limestone Member (Pliocene). Noble and Henk (1998) showed that the
Paciran Limestone Member is a deep-marine pelagic carbonate deposit.
The lower lithofacies are mainly grainstones, wackestones, and packstones,
and the upper lithofacies predominately comprise marls. The upper marl litho-
facies of the Paciran Limestone contains abundant, gas-charged Zoophycos . The
Zoophycos are backfilled with hollow globeriginid tests ( Fig. 9 ), and the trace-
fossil permeability is substantially higher than the matrix. The ichnogenus is
deeply penetrative; so, the burrows are interconnected and the permeability
is isotropic.