The Higher Mining Office (WUG) published a report on the safety and accident rate at oil and gas exploration in the years 2010 through 2014.
Shale gas exploration is inherently safer than exploratory conventional gas drilling operations. Usually, “common” natural gas is highly pressurized in natural traps of permeable rocks. As a consequence, the risks are much greater comparing with unconventional gas exploration.
Shale gas accumulations occur in non-permeable rocks. Fractures must be induced in the rock in order to release and produce the gas at high flow rates. Fracture stimulation is used to establish pathways for natural gas flow to the borehole. These operations require a strict control to ensure safe delivery and minimize inherent risks that are associated with high pressures involved.
From 2010 to 31 December 2014, 68 shale gas exploration wells have been drilled (one well is in drilling). In 2014 alone 12 wells were drilled and further 5 wells started in 2013 were completed. Moreover, 10 diagnostic fracture injection tests and fracture stimulation jobs were made, including five 1000.0 to approx. 1500.0 m long fracture stimulation operations in horizontal legs.
Exploratory drilling (for both conventional and unconventional gas) involves natural risks such as blowout and hydrogen sulfide gas. Moreover, exploration, appraisal and extraction of mineable resources, including hydrocarbons, are associated with other risks, including:
- fire risk,
- explosion risk,
- breathing risks for workers,
- ground collapse,
- underground natural gas storage risks,
- gas migration,
- offshore oil and gas production risks.
Drilling and E&P companies reported the following accident rates in the years 2010 through 2014:
- in 2010 - 34 accidents,
- in 2011 - 30 accidents,
- in 2012 - 26 accidents,
- in 2013 - 25 accidents,
- in 2014 - 37 accidents (11-month data).
For comparison, 9 645 accidents (of which 79 fatal) and 2 063 accidents (of which 17 fatal) have been reported by coal and copper ore mines, respectively, in the same period of 2010 - 2014.
The most frequent causes of accidents at work reported by oil and gas industry from 2010 through 2014 were:
- delivery of operations that are not included in job description,
- operations delivered in a manner which is inconsistent with good drilling practice and instructions,
- working in unbreathable air environments,
- inadequate work focus and the routine factor.
From 2010 to 2014, the following accidents at shale gas exploration have been reported:
- one fatal accident (failing drill pipe struck a drilling crew member),
- one death for natural causes,
- one case of electric arc burns.
Like in previous years, not a single case of an environmental or health hazard occurrence was reported in 2014. Thirty five audits performed by mining supervision authorities did not reveal any irregularities that would pose a health or life risk to the drilling crew.
The most frequently reported irregularities involve operation of plant and machinery in violation of applicable regulations (decisions to suspend their operations until restored to good technical condition and missing documentation supplemented), including inadequate protection of rotating parts (the irregularities have been removed on an ongoing basis).
The irregularities found have been removed on an ongoing basis. Disciplinary measures included explanatory proceedings, instructions, warning and fines.
In 2014, accident rate at conventional gas exploration and production operations was lower than in the case of shale gas exploration. Crude oil production involved a single fatal accident at work: a service company worker died while cleaning a separator tank.
Blowout and hydrogen sulfide risks
In terms of potential blowout risks, Poland is divided into:
- low risk areas: Carpathian Mountains and the Carpathian Foredeep,
- medium risk areas: Lublin Monocline and developed fields with depleted reservoir pressures,
- very high risk areas: Fore-Sudetic Monocline and Northwest Polish Lowlands with Main Dolomite and Rotliegend formations as key risk areas.
Hydrogen sulfide risk occurs in oil and gas drilling operations conducted in the Fore-Sudetic Monocline and Polish Lowlands areas when drilling through Permian, in particular Main Dolomite, formations. In fractured Dolomite reservoirs, H2S concentrations in reservoir fluids may be as high as 18%. The risk tends to decrease gradually with the progress of production and reservoir pressure gradient reduction.
A blowout and hydrogen sulfide risk was reported in 2014. A sour gas blowout occurred while drilling a tight gas well in Wielkopolska. Hydrogen sulfide concentrations have been monitored during blowout control operations. Drilling crew and the environment were found to be safe.
Ground collapse, other serious drilling hazards or failures posing a risk to the environment and drilling crews were not reported in 2014.
source: The Higher Mining Office (WUG)