Published November 2025, Pg. 25-33

Section: Oil and gas preparing and transportation

UOT: 622.691.4

DOI: 10.37474/0365-8554/2025-11-25-33

Cascade shock-wave technology for the elimination of complete hydrate blockage in subsea marine gas pipelines

A.N. Baghirov PhD in Tech. Sc. - Azerbaijan State Oil and Industry University

F.Q. Seyfiyev PhD in Tech. Sc. - Azerbaijan State Oil and Industry University

U.R. Taghizade - Azerbaijan State Oil and Industry University

N.G. Amiraslanli - Azerbaijan State Oil and Industry University

The article investigates the prediction of hydrate formation conditions during the transportation of natural gas through subsea main gas pipelines and the methods for eliminating the stage-wise complications arising in this process. For the first time, a theoretical explanation of the newly developed cascade-shock-wave technology aimed at completely removing hydrate blockages in gas pipelines is presented, along with a description of its practical application. The specificity of hydrate formation characteristics in subsea gas pipelines and the unsuitability of methods developed for onshore conditions under marine environments are emphasized. Additional factors affecting hydrate formation processes and their elimination methods are identified; in particular, the colder temperature at the pipeline’s burial depth and the impossibility, unlike onshore, of installing additional pressure and temperature measurement devices along the pipeline are highlighted.
The author presents a systematization of the stages of hydrate formation in offshore trunk gas pipelines, along with corresponding risk prediction and mitigation methods tailored to each stage. The theoretical foundations and mathematical models of the proposed cascade-shock-wave technology—which is based on the cyclic injection of high-pressure gas into a previously decommissioned and depressurized pipeline due to an emergency—are thoroughly analyzed. The analysis of high-pressure gas dynamics reveals that, due to the increased speed of sound in the preheated gas, subsequent compression pulses overtake the preceding ones, ultimately leading to the formation of a shock wave front.
The constricted sections formed in the pipeline as a result of condensate accumulation function as natural nozzles (soplos), and gas flows repeatedly passing through these narrow zones reach supersonic velocities. The operational procedure for eliminating a hydrate plug in a real gas pipeline has been described, and the temperature regimes at the contact point have been calculated, establishing the dependence of this temperature on the pressure of the injected high-pressure gas. Although the temperature at the contact surface increases significantly, the brevity of this thermal effect (lasting only a few seconds) justifies the cyclic injection of high-pressure gas into the pipeline in multiple stages.
The developed and successfully tested cascade-shock-wave technology is based on the combined effect of thermal melting of the hydrate due to the temperature rise at the contact interface and the simultaneous dynamic wave action of the gas flow.

References:

1. Makagon Yu.F. Gidraty prirodnyx gazov. – M.: Nedra, 1974. 208 s.

2. Iskandarov E.Kh., Baghirov A.N., Shikhiyeva L.M. Method for assessing the hydrate formation from a mixture of natural gas flows of varying degrees of moisture content. “Nafta-Gaz”, Krakow, Poland, 2024, no. 1, pp. 39-44.

3. Istomin V.A, Kvon V.G. Preduprejdenie i likvidatsiya gazovyx gidratov v sistemax dobichi gaza. PM: ООО “IRS Qazprom”, 2004, 506 s.

4. Istomin V.A, Yakushev V.S. Gazovyye gidrati v prirodnykh usloviyakh. – M.: Nedra, 1992, 236 s.

5. Zhou S., Chen X., He C., Wang S., Zhao S., Lv X. Experimental Study on Hydrate Formation and Flow Characteristics with High Water Cuts. Energies 2018, 11, 2610.

6. Tathagata Acharya, Kelly Pierce, Meagan White. Natural Gas Hydrates: A Review of Formation, and Prevention/Mitigation in Subsea Pipelines. April 2019 Advanced Science, Engineering and Medicine. 11(6): 453-464.

7. Iskandarov E.Kh.  Analytıcal and wave-depressıon methods of elımınatıon of the onset of hydratıon ın subsea gas pıpelıne / E.Kh. Iskandarov, Sh.A. Baghirov // News of the National Academy of Sciences of the Republic of Kazakhstan / Series of geology and technical sciences, v. 4, Number 454 (2022), 96-108.

8. Iskandarov E.Kh. Determining of primary hidrate formation in subsea gas pipelines / E.Kh. Iskandarov, A.N Baghirov, Sh.A. Baghirov // International Scientific-Practical Conference Khazar Oil Gas Field (ISPC KOGF-2022), Proceeding of Scientific Papers. 6-7 Desember 2022, Baku, Azerbaijan. Scientific Research İnstitute “Geotechnological Problems of Oil, Gas and Chemistry”, p. 22-27.

9. Bulovich S.V., Vikolaynen V.E. Volnovoe dvijenie gaza v protyajennix kanalax: Ucheb, Posobie, SPb: Izd-vo Politex, un-ta, 2006, 68 s.

10. Zel′dovich Y.B. Teoriya udarnyx voln i vvedeniye v gazodinamiku. – Moskva-Ijevsk: NITS “Regulyarnaya i khaoticheskaya dinamika”, 2002, 186 s.

11. Baghirov A.N. Supersonic cooling technology of gas turbine air “Energy technologies and resource saving”, Kiyev, Ukraine, v. 81, no. 4 (2024), pp. 79-87.

12. Iskandarov E.Kh., Baghirov A.N., Baghirov Sh.A., Ismayilova P.Sh. Razrabotka novykh texnologicheskikh processov na osnove sverkhzvukovogo techeniya gaza // “SOCAR Proceedings”, 2020, № 4, s. 117-123.