(CNN) -- The flow of oil leaking from a North Sea oil platform east of Aberdeen, Scotland, has been "greatly reduced," and no oil is expected to reach land, the British Department of Energy and Climate Change and a Shell official said Monday.

An estimated 1,300 barrels of oil have escaped through the leak in a pipeline at the Gannett Alpha platform, Shell said Monday. The pipeline is now leaking about five barrels of oil daily, the company said.

It's unclear exactly when the leak began or what caused it. The leak was reported last week.

High winds and waves over the weekend broke up much of the surface sheen visible around the leak, said Glen Cayley, technical director of Shell's exploration and production activities in Europe. The oily patch on the surface covers about half a square kilometer (nearly 0.2 square miles).

"We continue to expect that the oil sheen will disperse naturally due to wave action and that it will not reach the shore," he said in a prepared statement.

The Department of Energy and Climate Change echoed that assessment in a statement issued Monday.

Scottish Environment Secretary Richard Lochhead said government officials are continuing to monitor the leaking pipe, which is located about 180 kilometers (some 110 miles) east of Aberdeen.

"As is standard practice in incidents such as this, the UK government, which has responsibility for the pipeline system, will be taking forward an investigation and I will be pressing for the Scottish government to have a full and formal role, given our responsibilities for the marine environment," Lochhead said in a statement.

The leak is small compared to the Gulf of Mexico oil spill in the United States in 2010, but is substantial for the region, the Department of Energy and Climate Change said.