«Proceedings of Gubkin University»

Mechanism of loss of annulus integrity during development of gas fields and operation of underground gas storage

UDC: 622.276
DOI: 10.33285/2073-9028-2023-2(311)-43-55

Authors:

¹ Institute of Oil and Gas Problems of the Russian Academy of Sciences, Moscow, Russian Federation

Keywords: bottom-hole zone of a well, underground gas storages, destructive stresses in the rock, depressurization of the annulus, spring centralizer

Annotation:

The paper presents the results of mathematical modeling and numerical analysis of the mechanism of destructive stress concentration in the near-wellbore zones of wells during the development of oil and gas fields and the operation of underground gas storages (UGS) and the resulting loss of integrity of the well annulus. The relevance of the study is substantiated by the existence of the problem of losses of produced hydrocarbons through the annulus of wells during field deve-lopment, gas storage in UGS facilities, as well as the problem of penetration of toxic liquids used in hydraulic fracturing of productive formations into water-saturated formations. It is shown that under the influence of shear stresses, the most likely destruction of the connection between the cement sheath and the walls of the well, since this connection is weakened by the existence of clay cake residues on the walls of the well. The destruction of this connection is accompanied by displacement of the rock along the wellbore relative to the casing string and depressurization of the annulus of the well. As a result of the studies, it was found that with a significant change in reservoir pressure in the bottomhole zones of wells or in the reservoir as a whole, destructive shear stresses concentrate in the near-wellbore zones of the wells near the roof of the productive reservoir. The maximum value of developing shear stres-ses is commensurate with the amplitude of changes in reservoir pressure, which during the operation of hydraulic fracturing is measured by ~30–50 MPa, ~15–18 MPa at the stage of gas injection into UGS, values of the order of ~10–20 MPa and more during field development depletion, which is typical for the development of gas fields. To prevent the expansion of the area of depressurization along the wellbore, a method is recommended, which consists in the fact that at the stage of well construction in the roof near the productive formation, its wellbore is expanded, and a spring centralizer with a nominal diameter exceeding the initial diameter of the wellbore is installed in the casing string in the appropriate place. After cementing the annular space of the well, a strong rigid inclusion is formed on the expanded section of the roof of the formation, reinforced with metal elements of the centralizer, which prevents the area of depressurization of the annular space from spreading along the wellbore during deformation processes in the rock caused by changes in reservoir pressure.

Bibliography:

1. Ustarevshie neftegazovye tekhnologii dobychi kak istochnik predstoyashchih ekologicheskih kataklizmov/S.N. Zakirov, E.S. Zakirov, I.M. Indrupskij [i dr.]//Ekologicheskij vestnik Rossii. – 2019. – № 8. – S. 20–25.
2. Abandoned oil and gas wells are leaking methane across the USA. – URL: http://inhabitat.com/abandoned-oil-and-gas-wells-are-leaking-methane-across-the-USA (data obrasheniya: 24.02.2023).
3. Plugging and abandonment of oil and gas wells//Working Document of the NPC North American Resource Development Study Made Available September 15, 2011, P. 2–25. – URL: http://www.npc.org/Prudent_Development_Topic_Papers/2-25_Well_Plugging_and_Abandonment_Paper.pdf (data obrasheniya: 24.02.2023).
4. Verzhbickaya V.V., Shchekin A.I., Yagudina L.V. PHG: analiz metodov sokrashcheniya emissii metana//Neftegaz.RU. – 2023. – № 2. – C. 38–46.
5. Rybalov E.A., Fomina Ek.E., Fomina El.E. Primenenie metoda ekspertnyh ocenok pri analize opasnosti neftyanyh i gazovyh skvazhin v sostoyanii konservacii ili likvidacii//Zashchita okruzhayushchej sredy v neftegazovom komplekse. – 2022. – № 2 (305). – S. 49–55.
6. Dolgov S.V., Velichko E.I., Nizhnik A.E. Osobennosti ekspluatacii i remonta skvazhin PHG// Stroitel’stvo neftyanyh i gazovyh skvazhin na sushe i na more. – 2022. – № 9 (357). – S. 47–50.
7. Crustal Deformation in the Hutubi Underground Gas Storage Site in China Observed by GPS and InSAR Measurements/Q. Xuejun, C. Wei, W. Dijin [et. al]//Seismological Research Letters. – 2018. – № 89 (4). – P. 1467– 1477.
8. Zheltov Yu.P. Mekhanika neftegazonosnogo plasta. – M.: Nedra, 1975. – 216 s.
9. Barenblatt G.I., Entov V.M., Ryzhik V.M. Dvizhenie zhidkostej i gazov v prirodnyh plastah. – M.: Nedra, 1984. – 211 s.
10. Svalov A.M. Mekhanika processov bureniya i neftegazodobychi. – M.: Knizhnyj dom “Librokom”, 2009. – 256 s.
11. Svalov A.M. K resheniyu problemy kachestvennogo krepleniya neftyanyh i gazovyh skvazhin//Geologiya, geofizika i razrabotka neftyanyh i gazovyh mestorozhdenij. – 2022. – № 5 (365). – S. 58–62.
12. Muskhelishvili N.I. Nekotorye osnovnye zadachi matematicheskoj teorii uprugosti. – M.: Nauka, 1966. – 708 s.
13. Pat. 2775849 Ros. Federaciya, MPK E21B 33/10. Sposob povysheniya germetichnosti zatrubnogo prostranstva neftyanyh i gazovyh skvazhin (varianty)/A.M. Svalov; patentoobladatel’ A.M. Svalov. – № 2021135972; zayavl. 07.12.2021; opubl. 11.07.22, Byul. № 20.