Page 160 - Geology of Carbonate Reservoirs

REVIEW QUESTIONS 141

SUGGESTIONS FOR FURTHER READING

Extensive discussions of carbonate depositional environments from the strandline
to the basin are presented in the AAPG Memoir 33, Carbonate Depositional Envi-

ronments (Scholle et al., 1983 ) . Individual papers are well illustrated with photos
and diagrams, most of which are in color and extensive citations from the research
literature are included. Good descriptions of carbonate depositional facies and
vertical successions from a variety of environments and geographic locations are
presented in Walker and James (1992) , Facies Models: Response to Sea Level Change .
A standard reference on depositional facies is by Reading (1996) , Sedimentary
Environments: Processes Facies, and Stratigraphy, 3rd edition. Cool Water Carbon-

ates (James and Clarke, 1997 ) contains a variety of papers to illustrate the range of
characteristics in temperate and cool - water carbonates. The most recent, compre-
hensive textbook on carbonate sedimentology is Carbonate Sedimentology by
Tucker and Wright (1990) . They provide detailed discussions on carbonate deposi-
tional environments, diagenesis, and geological trends in carbonate sedimentation
through time. Wilson ’ s 1975 book, Carbonate Facies in Geologic History , is an excel-
lent review of carbonate depositional systems by geological age around the globe.
Carbonate depositional systems are examined in sequence - stratigraphic context in
Carbonate Sequence Stratigraphy (Loucks and Sarg, 1993 ).

REVIEW QUESTIONS

5.1. In purely depositional reservoirs, there are four pore types found in detrital

carbonates. What are they?

5.2. Beach – barrier island successions consist of lower shoreface, middle shoreface,
and upper shoreface segments. What physical oceanographic processes deter-
mine the depth at which the lower shoreface segment grades into the shallow
subtidal environment?

5.3. What are some distinctive sedimentary structures in dunes that make them
relatively easy to distinguish from beach successions?
5.4. We know that OOIP = 7758 Ahφ (1 − S w )/ B oi . Use a reservoir model based on
the Pleistocene outcrops near Isla Cancun in Yucat á n where dunes are about

30 m in average height, 100 m in average width, and extend about 7 km along
the eastern rim of the island (Ward, 1975, 1997 ). Consider only a small segment
of the total complex in which the hypothetical reservoir is 6 m (20 feet) thick
above the oil – water contact. The reservoir is 4 miles long and 330 feet wide,
or about 160 acres in map area. Average porosity is 15%, and S w = 30%.
Assume B oi is 1.0.
(a) What is the estimated OOIP of our 160 - acre fi eld?

(b) In most reservoirs, the amount of recoverable oil is about 30% OOIP.
Using an oil price of $ 75/barrel, what is the estimated dollar value of the
oil in place?
(c) If we develop the field on 40 - acre spacing, what is the average dollar value

of each well?