The Nation
July 9, 1996

Unocal to dump waste via deep-well injection

PLATONG PLATFORM, GULF OF THAILAND - Unocal Thailand hopes to dispose of
its mercury-contaminated water by re-injecting it back into disused
wells, rather than releasing it into the sea as it is currently doing.
        The waste disposal method _ known as deep-well injection _ is a
``proven technology' that has been approved by the US Environmental
Protection Agency, according to Unocal officials.
        It remains controversial with environmentalists, however, who
fear that it will contaminate the environment with toxic waste in the
long run.
        Mercury is a dangerous neurotoxin which builds up in the food
chain and causes damage to the central nervous system when ingested by
humans. Natural gas produced from wells drilled under the Gulf of
Thailand is contaminated with the substance.
        Unocal, a gas concessionaire with 87 platforms in the gulf,
already disposed of 1,459 barrels of mercury-contaminated sludge last
July by sending them into disused wells. The company received approval
for the operation from the Department of Mineral Resources (DMR) and
claims it was successful.
        Prakan Boonchuaydee, head of the Toxic Waste Management Division
at the Pollution Control Department (PCD), said he was not informed
about the matter and questioned whether it was appropriate. Unocal will
hold talks with the PCD later this week.
        Unocal has also received approval from the DMR to test the
deep-well injection method for disposing of mercury-contaminated water
which is brought up from underground along with the gas. The trial is
due to be held next month.
        But disposing of the water in this manner is likely to be more
difficult than the sludge because there is such a huge volume of it,
according to Tawatchai Siripatrachai, manager of Unocal's environmental
programmes.
        The underground reservoirs may simply be too small to hold all
the produced water, he said, or the water may chemically interact to
plug up the reservoir.
        Unocal is therefore also attempting to improve its water
treatment system. On its Platong platform, it has reduced the mercury
content of water discharged into the sea down to an average of 80 parts
per billion (ppb) with the help of a water purifying device known as a
hydrocyclone.
        Without the device, Unocal officials said, its discharged water
contains 150-200 ppb of mercury on average, although the amount
fluctuates a great deal. This is cited as the main cause of mercury
contamination in the fish around Unocal's platforms.
        The US-based petroleum firm has yet to release its complete data
on fish contamination to the public, but says it is prepared to do so.
        Prof Dr Piamsak Menasveta, a marine scientist at Chulalongkorn
University who carried out the fish surveys, says the number of fish
around the platforms with mercury levels over the standard has risen to
nearly 10 per cent.
        Unocal officials took a group of environmental journalists from
the Thai press on a tour of its waste dispsal facilities over the
weekend.
        Tawatchai said Unocal had waited in vain for many years for
Thailand to build a toxic waste treatment facility in order to dispose
of its sludge. In 1993, the company considered building its own
distillation plant to separate out the mercury - a process some
environmentalists consider safer than deep-well
injection - but decided against it for fear of ``Nimby' (``Not in my
backyard') protests by local villagers.
        He added, however, that Unocal favoured the deep-well injection
method because it results in ``zero discharge' of mercury, and not
because of Nimby concerns or because it is cheaper than other methods.
        Building the distillation plant would have cost US$800,000 (Bt20
million) plus operating costs, he said. The deep-well injection
operation last year cost $400,000-$800,000 (Bt10-20 million). Toxic
sludge is continually being produced and another 600 barrels are now
sitting in a warehouse in Songkhla, awaiting injection.
        Unocal officials downplayed fears that mercury-contaminated
waste would leak from the wells, saying it is surrounded by special
cement which will last ``at least 100 years'. It is buried so deeply and
so far from shore that it won't affect underground water supplies or
contaminate benthic fauna on the sea floor, they added.
        They also said the waste could not travel through the
underground reservoirs and emerge through other wells because the
injection site is specifically chosen to be isolated.
        In testing out the process for its produced water, Tawatchai
said, Unocal will not add chemicals to kill off any bacteria in the
water. He added that the process will not lead to leaks of hydrogen
sulfide, a dangerous gas which could be produced by sulfate-eating
bacteria in the water, because the injection process will be carried out
continuously.