Report On Sarir Oil Field: Well Intervention Workover and Stimulation Techniques (PTE-432)
Report On Sarir Oil Field: Well Intervention Workover and Stimulation Techniques (PTE-432)
Report On Sarir Oil Field: Well Intervention Workover and Stimulation Techniques (PTE-432)
BY
ANDREW VIJAI J
Submitted to
LOCATION:
The Sarir or, more specifically, the Sarir "C" field lies on the
western edge of the Calanscio Sand Sea in southern Cyrenaica
and is the largest oil field in Libya. It occurs at the southeastern
margin of the Upper Cretaceous-Tertiary Sirte basin or
embayment that contains all the major oil fields of Libya and is
the most prolific oil-producing basin in North Africa (Figure 1).
Other significant fields lying in the same basin are Amal, Gialo,
Nasser (Zelten), Defa, Augila, Hateiba, Messla, Intisar A and D,
Bu Attifel, Raguba, and Bahi.
Estimated ultimate recovery from the "C" field is 6.5 billion bbl
of oil and, from the "L" field, 1.2 billion bbl, ranking them as the
51st and 201st largest fields in the compilation of Carmalt and
St. John (1986).
HISTORY
Pre-Discovery
Discovery
The actual first recognition of the discovery of the Sarir field
makes an interesting story. For years BP had been cool to the
use of gas detectors on its rigs. It claimed, with some
justification, that they caused too many false alarms. However,
in late-1961, Baroid were brought in to set up gas detectors on
BP's Libyan wells. A demonstration was given on C-1-65, when
drilling was taking place in the "caving Cretaceous shales," for
all the rig-site geologists to witness. The gas detector gave very
high readings the moment it was switched on. This was
immediately assumed to be a typical gas detector false alarm,
but, when the whole apparatus was cleaned out and new
elements fitted, the same high readings persisted. Then, on
carefully examining the samples of "shale cavings," at the bo
tom of the plates were found loose grains of oil-stained sand.
Approximately 200 ft (61 m) of oil pay had been drilled!
Statistic Amount
Crude gravity 37° API
Wax content 19%
Sulfur content < 0.25%
Reserves 12 Gbbl (1.9 km3)
Ultimate recoverable
6.5 Gbbl (1.03×109 m3)
reserves
1.5 Gbbl (240,000,000 m3) (1983
Cummulate production
est.)
PETROLEUM SYSTEM OF SARIR FIELD
The petroleum system consist of :
SOURCE ROCK
MIGRATION
ACCUMULATION
RESERVOIR
SEAL
TRAP
MIGRATION:
Migration probably commenced in the early tertiary when
the source rock is sufficiently buried to attain maturity for oil
generation.
RESERVOIR:
The Sarir Sandstone Formation of Upper Jurassic to
Lower Cretaceous represents the main hydrocarbon
potential reservoir in the Chadar Field. The Sarir Sandstone is
distributed widely in the subsurface of the study area and it is
composed of a thick sandstone unit interbedded with shale.
SEAL:
TRAP:
Sarir is contained in a structural-stratigraphic trap,
represented by dips to the east, south, and west and the major
northeast-southwest-trending fault on its northwest flank. In
much of the central and northwest, the reservoir subcrops and
is sealed by shales that unconformably overlie it.