A multifaceted approach to oil and gas wells workover on the last stage of field development is considered. One of methods aimed to oil and gas well recovery is a coiled tubing technology that is recently widely being used during the well workover. Existing technologies of well workover by means of coiled tubing unit usage become often complicated because of the pipe sticking and further twist-off due to limited technical capacities of the coiled tubing unit that leads to irretrievable consequences during emergency works. On this basis, a necessity of technical accident risks estimation on the stage of well workover design aimed to reduce labor, material and financial resources is justified.
On the base of well workover experience analysis the authors determined a probability of coiled tube twist-off during squeeze cementing works with the help of coiled tubing unit. This method permits to estimate and to compare different danger risks within the same indicators and gives a possibility to determine numerically a frequency of negative events; this will permit to reduce significantly risks of the accident initiation and in general will improve the well workover quality. Taking into account the specificity of the well workover and the possible coiled tube sticking and further twist-off, the authors suggested a technology of coiled tubes removal with the help of the coiled tubing unit. This method permits to make emergency works in a well without such operations as well killing and replacement of the coiled tubing unit by a mobile hoist that represents quite a difficult task (sometimes unreal) during the tubes twist-off elimination operations in conditions of abnormal low formation pressures and high formation permeability.
An addition to the
structure of the current workover classification, that characterizes a workover
according to its type and method of realized works in a well, is justified.
With the help of the proposed information block, the companies specializing in
well workovers will be able to justify a workover period and consequently its
cost that is the most important indicator in current conditions of the
contractors tendering process.
References
1. Vaganov Yu.V., To the issue of methodological support of wells overhaul at the present-day stage of fields development (In Russ.), Izvestiya vuzov. Neft' i gaz, 2014, no. 6, pp. 19–22.
2. Kustyshev A.V., Vaganov Yu.V., Dolgushin V.A., Arrangement of wells overhaul repair operation under present-day conditions of oil and gas fields development (In Russ.), Izvestiya vuzov. Neft' i gaz, 2015, no. 6, pp. 19–25.
3. Kustyshev A.V., Slozhnye remonty gazovykh skvazhin na mestorozhdeniyakh Zapadnoy Sibiri (Complex gas well servicing in Western Siberia), Moscow: Gazprom EKSPO Publ., 2010, 255 p.
4. Molchanov A.G., Vaynshtok S.M., Nekrasov V.I., Chernobrovkin V.I., Podzemnyy remont i burenie skvazhin s primeneniem gibkikh trub (Well servicing and drilling with coiled tubing), Moscow: Publ. of Akademii gornykh nauk, 1999, 224 p.
5. Vaganov Yu.V., Methodology of well workover realization under presentday conditions of Cenomanian reservoir development (In Russ.), Izvestiya vuzov. Neft' i gaz, 2016, no. 1, pp. 34–38.
6. Kustyshev A.V., Vaganov Yu.V., Zhuravlev V.V., Risk assessment for oil and gas wells workover (In Russ.), Bezopasnost' truda v promyshlennosti, 2013, no. 9, pp. 76–82.
7. Vaganov Yu.V., Kustyshev A.V., Leont'ev D.S., Gagarina O.V., Fishing operations in oil and gas wells using coiled tubing (In Russ.), Vremya koltyubinga, 2015, no. 2, pp. 46–52.
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