- From a standing start in 2009, natural gas production from the Marcellus Shale in Bradford County Pennsylvania (PA) now exceeds 2.2 billion cubic feet (bcf) per day from 728 wells (to end June 2013).
- To put this in perspective, the UK consumes about 8 bcf per day and so 4 Bradford counties (about 3000 wells) could make the UK self- sufficient.
- The catches are that Bradford County is a production sweet spot – you have to find the sweet spots before you can produce them. And to keep production going, over a hundred new wells need to be drilled every year.
- 6 charts below the fold show the production history, average well productivity and decline rates from Bradford County.
Figure 1 This chart shows the production stack for 728 Marcellus shale gas wells, Bradford Co. PA. XL would only let me plot about 150 data series and so the wells are aggregated into production from groups of 5 wells. The black line shows the number of producing wells, right hand scale. Data from the Pennsylvania Department of Environmental Protection (DOEP). Click on all charts to get a larger version that will open in a new browser window.
My next post will be titled “Shale gas myths and realities” and for that post I want to try and quantify the type of impact that shale developments may have on communities in Europe. One of the most important factors is the number of wells and that depends upon well productivity. I went looking for data and came across the Pennsylvania Department of Environmental Protection shale gas portal. This provides production figures for all counties aggregated into 6 month periods.
A lot of drilling activity in Bradford County suggested this was a production sweet spot and I began looking at this data simply to get a handle on typical flow rates. I ended up looking at over 700 wells which was a more extensive analysis than I originally planned.
All geologists and petroleum engineers already know that shale plays experience high decline rates compared with conventional reservoirs. This is important for the man on street to know because once you go down the shale route, you are making a commitment to drill more and more wells every year to keep production going. Decline is a phenomenon that affects all wells (conventional and unconventional) which results in production falling from one year to the next.
Figure 2 Chart showing only wells that were brought into production Jul-Dec 2009 and Jan-Jun 2010. Decline rates shown as % numbers relative to the production from the preceding year. Decline for 2013 is calculated by doubling the production recorded Jan to Jun and comparing that with 2012 (applies also to Figures 3 and 4). This will tend to underestimate the decline. On all charts, years are shown in duplicate, the first date is for Jan to Jun and the second for Jul to Dec. That is apart from 2009/2 and 2010/1 where the data are aggregated for 12 months by DOEP (not a calendar year).
Figure 2 shows only the wells drilled and brought on stream Jul-Dec 2009 and Jan-Jun 2010. All the wells drilled subsequently (Figure 1) are not plotted and this provides a clear picture of the aggregate decline in these first shale wells drilled in Bradford County. Production in 2011 fell by 42% compared with the year before. Year 2 (2012) showed a 31% decline and year 3 (the first 6 months of 2013) a 22% decline. Had the drillers not kept drilling, production in Bradford County would now be 100 million cubic feet per day as opposed to the 2.2 billion cubic feet per day at end June 2013. The intensity of drilling required to deliver the 2.2 billion cubic feet per day “miracle” is shown in Figure 7. And so it is clear, to keep shale production going you have to drill – lots and lots of wells.
Figure 3 is the equivalent to Figure 2 but for wells brought on line in the second half of 2010. Note how for a similar number of wells the aggregate production is 350 million cubic feet per day compared with 250 million cubic feet per day shown in Figure 2. And the first year decline is a lower 33%. The industry seems to be learning.
Figure 4 Same as previous two figures but for wells brought on stream the first half of 2011. Productivity once again is up and first year declines are down (see Figure 6.)
Figure 5 Summing the data shown in Figures 2, 3 and 4 produces this broad picture of how shale gas production has evolved in Bradford county, showing wells brought on stream up to June 2011. The picture is easily completed but it is time consuming to compile the data.
Figure 6 This figure shows the average well performance and how it has evolved over a very short 18 month period. The improved performance with time in Bradford County is quite clear.
Figure 6 is important because it shows how the industry is learning to drill shale better. There can be two factors at work here. The first is identifying better areas to drill. The second is drilling wells better, i.e. better well engineering to enhance flow rates. Watching how this type of chart evolves with time will provide clear indications to the long-term future of the shale gas industry. Once new wells begin to under perform old wells production will be overwhelmed by declines.
Figure 7 The drilling history in Bradford County PA.
In conclusion, European citizens seem concerned about every aspect of the infrastructure required to deliver the energy that is essential to provide them with the basic needs such as food, heat, light, work, health care, welfare, pensions, etc. It is time for citizens to start weighing the risks of infrastructure against the benefits of having heat and light, 24 hours per day, 7 days a week (24/7). There is no easy way, only difficult choices to be made. My next post will try to layout the risks and benefits of shale gas development in Europe.
Note that this technical post contains information that is of value to energy companies, investment companies, investors, policy makers, politicians, environmental regulators etc. It has taken over 2 days to compile this data. In future I will be providing a number of these data driven posts (1 to 2 per month) and feel that it is only fair that those who benefit pay for the service. Otherwise the service will inevitably end.
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