The drilling of horizontal wells in the last 6 years has significantly improved the economics of oil and gas production from depleted reservoirs or tight sands. This paper illustrates the application of an alcohol ethoxylate into a drill-in fluid designed to minimise formation damage in low permeability sandstones while drilling horizontal sections as long as 1,617 metres (5,306 ft) at depths approaching 6,580 metres (21,600 ft) and to facilitate formation cleanup.

The chemistry of alcohol ethoxylates/alkoxylates are described and the more popular names used within the industry will be discussed. Laboratory results are presented which illustrate colloidal phenomena not previously reported with these systems, the routes taken for successful application into a drill-in fluid and how complex these particular colloidal systems are from a physical chemical viewpoint, along with the inevitable "learning curve" required to fully optimise these systems.

Generalised case histories from the UK Southern North Sea will be described, along with field observations which back up the colloidal phenomena seen in the laboratory.

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