DECLINE RATES IN THE BAKKEN SHALE

摘要

For decades the oil industry has applied a simple rule estimating a constant"decline"rate in conventional oil wells.Typically production in an oil field declines at an annual rate of around 8% to 10%,absent further investment.This allows field production to be counted on for two decades or more.Shale oil development,however,has turned the rule of thumb on its head,with decline rates as much as 50% in the first year.In order to maintain oil shale production the industry must constantly drill new wells.This has led many analysts to reason that shale oil has become a balance wheel for the world oil market: low oil prices reduce the incentive to drill and within a few months reduced supply restores higher prices.Since 2014 this has been the observed paradigm,with shale oil waxing and waning as the market changed.Review of North Dakota Bakken shale oil wells,however,reveals a more complex story than that initially imagined.As noted,shale oil production declines rapidly in the first year,but the rate of decline appears to taper off after the first few months.Moreover,there is extraordinary variation in each well’s production pattern.Some wells produce for only a few months with output dropping fast,others act more like conventional production.Below is a graph of the average well production of Bakken Shale.