Studying Thermophysical Processes during the Filtration of Paraffin Oil to a Horizontal Well

About the authors:

Anatoliy A. Kislitsin, Dr. Sci. (Phys.-Math.), Professor, Department of Applied and Technical Physics, School of Natural Sciences, University of Tyumen, Tyumen, Russia; a.a.kislicyn@utmn.ru, https://orcid.org/0000-0003-3863-0510

Sergey V. Kuznetsov, Cand. Sci. (Phys.-Math.), Project Coordinator, Gazprom Neft Science and Technology Center (Tyumen); kuznetsov72tmn@gmail.com

Aleksandr A. Podnebesnyh, Cand. Sci. (Geol.-Mineral.), Deputy Academic Director, SIAM Company, Integra; apodnebesnykh@integra.ru

Vitaliy O. Polyakov, Leading Specialist, LLC Novatek Science and Technology Centre

Abstract:

In this article, the authors have formulated a system of equations of filtration paraffin oil to a horizontal well in view of phase transitions (degassing oil, wax crystallization), the Joule–Thomson effect, as well as geometric features of the system. It relies on the assumption that local thermodynamic equilibrium is achieved for all phases at each point of the porous medium at each instant of time. The authors have developed an algorithm for calculating phase equilibrium three-phase multicomponent mixture, based on the use of the thermodynamic functions of fugacity and activity. They have substantiated quasi-one-dimensional approximation of the equations describing the flow of formation fluid. They have also accounted for the effect of reducing permeability effect in the bottom hole zone as a result of the crystallization of paraffin. Based on the formulated system of equations, the authors have created a software package that allows simulating the process of filtration of a three-phase multicomponent mixture in the bottom hole zone of a horizontal well with good accuracy. The paper has investigated the process of crystallization of paraffin oil and shown that its speed is heavily influenced by oil disintegration (gas allocation from oil when pressure is reduced). The simulation of bringing the well to the technological regime has established that the dynamics of the change in bottom hole pressure significantly affects the final productivity factor of the well. The authors show that a too rapid decrease of the bottom hole pressure can lead to a noticeable temperature decrease, paraffin crystallization, a decrease in dynamic porosity, and deterioration in permeability. In accordance with the proposed method, the paper presents the patterns of the decrease in productivity of the well depending on the intensity of the bottom hole pressure decrease. Numerical experiments have determined the optimum dynamics of the bottom hole pressure in the process of development of the well after drilling in order to achieve a maximum productivity index.

References:

1. Aziz Kh., Settari E. 2004. Matematicheskoe modelirovanie plastovykh sistem [Mathematical Modeling of Reservoir Systems]. Moscow-Izhevsk: Institut komp'yuternykh issledovaniy.
2. Brusilovskiy A. I. 2002. Fazovye prevrashcheniya pri razrabotke mestorozhdeniy nefti i gaza [Phase Changes in the Development of Oil and Gas Fields]. Moscow: Graal'.
3. Vargaftik N. B. 1972. Spravochnik po teplofizicheskim svoystvam gazov i zhidkostey [Handbook on Thermophysical Properties of Gases and Liquids]. Moscow: Nauka.
4. Gibert D. P., Kovrigin L. A. 2007. “Modelirovanie protsessa otlozheniya parafina na stenkakh nasono-kompressornoy truby neftyanoy skvazhiny” [Simulation of the Process of Paraffin Deposition on the Walls of the Pump-Compressor Pipe of an Oil Well]. Vestnik PGTU, no 9 (1), pp. 15-23. 
5. Gazpromneft. 2014. Zaklyuchenie po rezul'tatam obrabotki dannykh GDIS skvazhiny № 14G Vostochno-Messoyakhskogo mestorozhdeniya: otchet o NIR [Resolution on the results of data processing from well no 14G of the East-Messoyakh Field: A Report on the Research Work]. Tyumen: Gazpromneft' NTTs. 
6. Kanevskaya, R. D. 2003. Matematicheskoe modelirovanie gidrodinamicheskikh protsessov razrabotki mestorozhdeniy uglevodorodov [Mathematical Modeling of Hydrodynamic Processes of the Development of Hydrocarbon Deposits]. Moscow-Izhevsk: Institut komp'yuternykh issledovaniy.
7. Kislitsyn A. A., Kuznetsov S. V., Podnebesnykh A. V., Polyakov V. O., Shabarov A. B. 2016. “Vliyanie razgazirovaniya na protsess kristallizatsii parafinov v nefti” [Influence of the Decompression on the Process of Paraffin Crystallization in Oil]. Delovoy zhurnal Neftegaz.RU, no 3, pp. 92-95.
8. Kislitsyn A. A., Fedorets A. A., Portnyagina E. V., Kuznetsov S. V., Podnebesnykh A. V. 2015. “Eksperimental'noe i teoreticheskoe issledovanie mikrokristallizatsii parafinov v nefti” [Experimental and Theoretical Investigation of Microcrystallization of Paraffins in Oil]. Tyumen State University Herald. Physical and Mathematical Modeling. Oil, Gas, Energy, no 3, pp. 14-23.
9. Kuznetsov S. V., Danko M. Ju. 2012. “Raschet fazovogo ravnovesija v sisteme ‘gazneft'—parafin’” [Calculation of Phase Equilibrium in the Gas-oil-paraffin System]. Neft'. Gaz. Novacii [Oil. Gaz. Novation], no 8, pp. 40-43.
10. Musakaev N. G. 2001. “O matematicheskikh skhemakh, opisyvayushchikh protsess kristallizatsii parafina v gazoneftyanykh skvazhinakh” [On Mathematical Schemes Describing the Process of Crystallization of Steam in Gas and Oil Wells]. Proceedings of International Conference RDAMM-2001, vol. 6, pt 2, special issue, pp. 318-322.
11. Gazpromneft. 2012. Tekhnicheskiy otchet. Analiz rezul'tatov laboratornykh issledovaniy prob nefti plasta PK1-3 Vostochno-Messoyakhskogo mestorozhdeniya: otchet o NIR [Technical Report. Analysis of the Results of Laboratory Studies of Oil Samples of the PK1-3 Reservoir at the East Messoyakh Field: A Research Report]. Tyumen: Gazpromneft' NTС.
12. Relative permeability models [Relative Permeability Models]. http://petrowiki.org/Relative_permeability_models#Models_for_three-phase_relative_permeabilities