Liquidation of Oil Prospecting Wells
Over-all Investigation and Technology Development for Liquidation of At-Conservation Oil Prospecting Wells in the Area of Inundation and Underflooding by the Caspian Sea in Mangystau Oblast of the Republic of Kazakhstan
Tech Area / Field
- ENV-RED/Remediation and Decontamination/Environment
- ENV-WPC/Water Pollution and Control/Environment
8 Project completed
Senior Project Manager
Rudneva V Ya
National Nuclear Center of the Republic of Kazakstan / Institute of Nuclear Physics, Kazakstan, Almaty
- Mangystau-Monitoring Ltd., Kazakstan, Aktau
- Natural Resources Canada / CETC-Devon, Canada, AB, Devon\nGrand Valley State University, USA, MI, Allendale
Project summaryObjective of the Project is to perform over-all environmental and technical works on assessment of technical conditions of underflooded and inundated wells, investigation of their influence on environment and development of rehabilitation measures for their liquidation including inpidual plans for conservation and liquidation of specific inundated wells in Mangystau oblast of the Republic of Kazakhstan.
In total on the territory of Kazakhstan there are more than 10 thousand oil-and-gas wells drilled by organizations of the former USSR [1-9]. Due to the deficit of budget financing most of the wells were temporarily conserved.
Temporary conservation was performed at different stages of oil deposits research and development. Temporarily conserved wells include: a) wells laid up at the stage of drilling; b) productive wells laid up for future commercial oil extraction; c) productive wells in the state of emergency.
The greatest hazard is presented by the wells in the state of emergency where liberation of gases including hydrogen sulfide and other petroleum products is observed.
Some productive wells are also unsafe, especially those being under pressure and conserved in anticipation of further extraction, the conservation period of which has expired long ago (exceeds 15-20 years). In many of such wells boring casing is worn out due to exposure to corrosive agents and at any moment the wells can cause immense emergency damaging of the environment. A special danger is presented by the wells in the area of the Caspian Sea flooding. Conservation and abandonment of oil field facilities and some oil wells were performed without due isolation from the impact of the corrosive sea water and glacial processes. At present, the technical condition of previously conserved wells requires their liquidation [1-9].
On fluctuations of the water level in the Caspian Sea. Waters in most of the North-East Caspian Sea are shallow and the depth is not stable. Significant long-term fluctuations of the average sea level have been observed. The level of the Caspian Sea dropped by almost three meters in the period of 1875 – 1977, but increased by 2.4 m in the period of 1977-1994. Average annual level dropped almost by 0.2 m per year in 1995 and 1996, but remained virtually the same in 1997 – 1999.
Depending on location of a well, on season and wave force there occurs ground washing around the wellhead (pedestal) of the previously conserved wells; as a result a casing string, with a concrete “mushroom” fixed on it, strips. The main damage to collars, pedestals and markers is caused by winter ice shearing and ice-hummocks formation. A string head and control equipment corrode actively in water and this process leads to oil, gas and water discharge/release due to leakage of casing pipes and a wellhead. Oil field facilities in operation (Kalamkas, Karazhanbas, Arman, Tenguiz, etc.) located in a coastal zone of the Caspian Sea and poorly protected from total flooding by frequently washed out dams constructed of local materials represent a danger as well and remain potentially hazardous in spite of permanent control of the dams condition. As we know from practice, these objects are also possible sources of the environment pollution and can cause major disasters. It is difficult to predict the effects of such disasters for biocenosis of the Caspian Sea.
According to available data, there are at present 38 oil fields and 39 oil-and-gas structures in the zone of flooding caused by the Caspian Sea; among them 9 oil fields and 15 structures are located in Mangystau oblast (according to information presented by Mangystau Territorial Oblast Department of Environmental Protection and Mangystau Oblast Authorities for Environmental Resources and Nature Use Regulation).
By present about 400 wells are located in the zones of flooding and underflooding by the Caspian Sea in Atyrau and Mangystau oblasts of Western Kazakhstan; 160 of them are in possession of oil field users and 240 wells are beyond the contract territories.
According to the data available by June 2003, three oil wells in Atyrau oblast leaked causing formation of oil patches/spots up to a kilometer lengthwise and 20-30 meters widthwise. In spite of the concerns declared and understanding of the urgent need in finding a radical solution of this problem, very few wells are under liquidation at present. A Kazakhstani newspaper “Novoye Pokoleniye” from 21.04.2004 reported the facts of oil leakage and described environmental problems with underflooded wells: By present in Mangystau oblast no one emergency well (flooded or underflooded) has been eliminated.
Territorial natural resources authorities hold tenders with the purpose to reveal such wells and work out measures/procedures aimed at their liquidation. One of the most dramatic problems in the course of flowing-out well liquidation is the depth of water which varies from 0 (in this case a profound layer of silt creates problems) to three meters. Such water depth complicates the application of traditional equipment designed for well liquidation.
Most of the wells subjected to liquidation were previously located on dry land. The liquidation technology did not ensure oil spillage prevention in case of well flooding. Quality of materials used in well liquidations does not correspond to the requirements to offshore wells. A significant amount of wells is damaged by corrosion, ice drifts and corrosive materials present in the boreholes (those are mainly harmful sulfide compounds, hydrogen sulfide H2S) and carbon dioxide.
Oil spillages affect dramatically the state of the Caspian Sea environment. As it was mentioned, different authors argue different volumes of oil escaping from leaky wells. In spite of difference in assessments, it is obvious that the wells in the zone of flooding represent a serious threat to the Caspian Sea environment. One of the results of harmful effects is degradation of vegetation and other forms of life reflected in the reports of state authorities for nature preservation and of non-governmental environmental institutions that have analyzed the situation.
Well abandonment in the zone of flooding is accompanied by the following problems [10, 11]:
- There is no any Regulation on abandonment of such wells that takes into consideration the specifics of works and hostility of the environment of the well after expiration of a certain period of time. Kazakhstan does not have any experience in such works.
- Wells can be covered with a water layer of various depth.
- Utilization of conventional drilling rigs, methods of their transportation and mounting-dismantling presents certain difficulties.
- Most wells were drilled 20-25 years ago and it is very difficult to evaluate their present technical condition due to unavailability of complete data.
- Technologies of well abandonment did not take into consideration measures on prevention of oil spillage into water.
- Corrosion of the above-ground part of collars of wells by sea water.
- Possible deformation of a collar by ice drifts.
- Difficulties of access to the well collar.
- Difficulties in finding the necessary information on the well in archives.
Highly professional personnel of the Institute of Nuclear Physics and the Company “Mangystau-Monitoring” Ltd. will allow to solve the above mentioned problems. At the INP NNC RK with the assistance of international organizations such as IAEA, ISTC, and others there is used advanced equipment and methods for determination of radionuclide and element composition in environmental objects. Instrumental and radiochemical methods certified and attested by State standardization authorities Gosstandard of RK have been developed and are successfully applied in environmental studies. The Company “Mangystau-Monitoring” disposes a staff of highly professional and skilled specialists experienced in abandonment of wells and sources of pollution along the Caspian Sea coastline. The Institute of Nuclear Physics and the Company “Mangystau-Monitoring” keep State licenses for engineering and ecologic research at the territory of the Republic of Kazakhstan and for abandonment of underflooded and inundated oil wells. INP NNC RK includes not only main laboratories, but also the Aktau representative office (Aktau, Magystay oblast), and the Aksay affiliate (Aksay, Western Kazakhstan oblast) in charge of operational control, field works and experiments. The Institute of Nuclear Physics has established a system of quality management corresponding to the requirements of the international standard ISO9000.
In the implementation of the planned works participate highly professional specialists – physicists, geophysiscists, chemists, engineers and technical personnel with significant experience in the field of nuclear physical, elemental and radionuclide methods of analysis, programmers specialized in creating and analyzing databases, modeling, geology and geophysics.
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