jordan_Outsourcing_book_temp.qxd 12/11/2009 13:10 Page 60
Well Blowout Rates in California Oil and Gas District 4 – Update and Trends
Figure 2: Oil and Gas Fields in District 4 Relative to Population Density
N
063 12 18 30 kilometres
0 24 8 12 20 miles
Persons per km
2
(mi
2
) Steam-injection wells
0–1 (0–2)
per km
2
(mi
2
)
1–4 (3–10) 0–0.1 (0–0.3)
4–15 (11–40) 0.1–1 (0.3–2.6)
16–62 (41–160) 1–9 (2.6–23)
62–247 (161–640)
9–81 (23–210)
247–988 (641–2,560)
>81 (210)
989–6,865 (2,561–17,785)
Source: Jordan and Benson, 2009.
6
storage wells in the EU prior to 2000 measured the blowout rates from activities, namely well construction, active wells and fluid volume. Well
these wells as one per 50,000 well-years.
9,10
These rates agree to within construction includes drilling, reworking and plugging  and
less than an order of magnitude, suggesting that operational well blowout abandoning. Slightly more than one-third of blowouts occurred during
rates are relatively constant from onshore to offshore environments and these activities. About one-fifth of blowouts occurred during
from primary production to enhanced recovery to gas storage. well servicing and one-third from wells in operation. The number
of well servicing operations is not available, so active wells is a proxy
Annual Blowout Update basis for this category of blowout.
The blowout data set assembled for the 1991–2005 study was updated
by interrogating the same data sources for the 2006–2008 period: the Fluid volume is also included in Figure 4. Fluid volume is the total
annual reports, digital database and paper records of the California amount of fluid injected and produced, including injected steam at
Division of Oil, Gas and Geothermal Resources, along with the wellhead conditions and produced water. Divided by the number of
Bakersfield Californian archive. No blowouts were described in the first active wells, fluid volume is somewhat of a proxy for wellhead
source, two blowouts were listed in the second, six blowouts had pressure, which has been posited as a primary parameter regarding
records in the third and no blowouts were described in the fourth. The well blowout rates.
6
two blowouts in the second source were a subset of those from
the third source. Figure 3 updates the annual number of blowouts As shown in Figure 4, field activity in District 4 did not decrease during
with the 2006–2008 data. This shows that the annual number of the study period. Therefore, the downward trend in the number of
blowouts in the District stabilised at the quadrennial average at the end blowouts is due to some factor other than changes in activity within
of the 1991–2005 study period. the District.
District-wide Annual Blowout Trend Specific Blowout Rate Trends
The annual number of blowouts in the District declined dramatically The annual and quadrennial average number of steam injection
during the 1991–2005 period. As noted in the District 4 study, this well blowouts and blowouts during well construction is shown in
could not be explained by changes in production activity in the District Figures 5 and 6, respectively. The number of steam injection well
during the period.
6
Figure 4 demonstrates this by superimposing the blowouts started decreasing in the late 1990s, and reduced to
annual number of blowouts on the trend in different well-field zero from 2001 to 2005. The number of blowouts during well
EXPLORATION & PRODUCTION – VOLUME 7 ISSUE 2
60
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