Abstract:
Oil and Gas production always ties with drawing out of
naturally-occurring radionuclides deposited beneath the earth,
which are referred to as “NORM”. Understanding the prevailing
background levels of these elements in the sub-surface reservoir
rock formations will be beneficial to all stakeholders, more
importantly to regulatory authorities of the country.
The drill cutting samples from 5 m sampling intervals of natural
gas reservoir sand section in the depth range 3025m to 3095m from
deep water exploratory well “CLPL- Dorado 91 H/1z” drilled in
the Mannar basin offshore Sri Lanka were tested in the laboratory
using high-resolution Gamma-ray detectors.
Test results revealed that the activity concentration of 40K,
210Pb,226Ra and 232Th levels and the calculated outdoor annual
effective dose rate varies between considerably lower range
when compared with the global standard limits.
NORM concentration ranges of the sedimentary rocks within
the tested section were recorded on the lower side, when the test
results compared with the International Atomic Energy Agency
published data on NORM concentration ranges of the sedimentary
rocks found elsewhere in the world. Study results proved that there
is no harmful public exposure of NORM by disposing these drill
cuttings to environment or storing at any site location as it is.
Also, it can be predicted that there will be very low level of
NORM contaminations occur, if Dorado reservoir taken in to the
production stage and well operations conducted with proper solid
control mechanisms in future.
