Reservoir Characterization and Estimation of Hydrocarbon Reserves of OJ-Field, Onshore Niger Delta, Nigeria4

Abstract

The reservoir characterization of OJ-Field in the eastern onshore of Niger Delta was determined using 3-D seismic
and well logs data. The main objectives are to access the potential reservoir sands with parameters that control its
hydrocarbon distribution, fluid type, identify structures necessary for hydrocarbon accumulation and estimation of
hydrocarbon reserves. Structural maps of horizons in four wells containing hydrocarbon bearing zones with tops and
bases at subsea depth range of -6723.93 to -9678.46ft were produced, showing the trapping mechanism to be mainly
fault-assisted roll-over structures. From the four reservoir sands delineated, Sand A (-6723.93 to -7143.18ft) is the
most prolific hydrocarbon bearing with 56.07MMbbl of oil and recoverable reserve of 6.46MMbbl while Sand C
(-8343.37 to -9203.15ft) is the second most prolific reservoir sand with 49.68MMbbl of oil and recoverable reserve
of 11.92MMbbl. Sand D (-8471.83 to -9678.46ft), which is the second least prolific, has 31.17MMbbl of oil,
112.74MMcf of gas and 0.94MMbbl recoverable reserve while the least prolific, Sand B (-7181.12 to -7877.56ft),
contain 26.05MMbbl of oil with recoverable reserve of 5.25MMbbl. Also, OJ-01 well was the most promising of all
the wells considered with 65.96MMbbl of oil and recoverable reserve of 5.21MMbbl compared with OJ-02 having
42.91MMbb of oil and recoverable reserve of 13.63MMbbl. OJ-04 is equally productive with 40.58MMbbl and
112.74MMcf of oil and gas respectively with recoverable reserve of 3.77MMbbl while OJ-03 is the least promising
well with 13.52MMbbl of oil that yielded recoverable reserve of 1.96MMbbl. The total net volume of the reservoirs
yielded stock tank oil in place of 162.98MMbbl and gas in place of 112.74MMcf. Only, 24.58MMbbl can be
recovered from the stock tank oil in place estimated and this is attributed to insufficient drive mechanism and high
viscosity.