see e.g.

"Chester 06 (Figure 29) is more encouraging. It shows a steep initial production followed by a plateau then a fairly steep decline and virtually no production tail. This field is significantly unlike the Dover 33 (superimposed dashed curve) even though it had about 92% of the Dover 33 total production. The initial production ratio (Chester 06/Dover 33) is close to 0.95 and the production curve does not show a pronounced double maximum, suggesting that the engineers either did not encounter heterogeneity problems or solved by drilling 3 wells here. Estimated secondary recov- ery: 456,000 barrels." (http://webcache.googleusercontent.com/search?q=cache:CykVxvD... )

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Note added at 9 mins (2015-11-24 13:07:21 GMT)
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"Naar huidig inzicht is er nog ongeveer 1.400 miljard kubieke meter winbaar gas. De afname van de gasproductie in Nederland zal geleidelijk plaatsvinden met een ‘productiestaart’ die waarschijnlijk nog vele decennia zal duren. Er kan dan ook nu geen moment worden genoemd waarop het gas op is. Wel kan opgemerkt worden dat diverse toekomstscenario's erop wijzen dat mogelijk rond 2025 Nederland netto-importeur van gas wordt." (https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web... )

You might want to stick "production tail" in scare quotes.

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Note added at 14 mins (2015-11-24 13:12:30 GMT)
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see also: http://seekingalpha.com/article/687501-the-long-tail-of-natu...