In this article we have reviewed an extensive range of studies of
clay swelling and its inhibition, covering experimental methods, along
with theoretical simulation techniques.
With ever more stringent environmental legislation and the need to
exploit oil and gas reserves in more environmentally sensitive areas, the
use of WBDFs is becoming more widespread. In this respect, the
development of more effective, environmentally friendly (low toxicity
and good biodegradability) clay swelling inhibitors for usewith WBDFs
is critical, particularly where highly reactive clay formations are
encountered. Materials which readily biodegrade will be less persistent
and less likely to accumulate in ecosystems. To achieve increased
biodegradability, swelling inhibitors based upon natural molecules/
polymers will need to be investigated. This adds an extra level of
complexity to the design of new and improved inhibitors as many
biodegradable polymers are not thermally stable under drilling condi-tions. The effective concentrations of drilling fluid additive, rates of
depletion and maintenance additions required for drillingfluid stability
must also be considered in assessing any potential risks to the
environmental and commercial viability