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Acid stimulation of oil wells using non-polymer diverter

UDK: 622.276.63
Key words: acid job/stimulation, non-polymer diverter, terrigenous rocks, hydraulic fracturing
Authors: A.E. Chikin (Rosneft Oil Company PJSC, RF, Moscow), M.N. Nikitin (Varyoganneftegazs PJSC, RF, Nizhnevartovsk), A.S. Petukhov, V.Yu. Fedorenko (Science-Technology Center ChemArt LLC, RF, Kazan), A.A. Zarov, A.A.Galiev (Samotlornefteotdacha JSC, RF, Nizhnevartovsk)

The heterogeneity of the reservoirs structure determines the complexity of a productive low-permeability formation processing due to high acid loss in the flushed zones. One of the ways to increase the efficiency of acid treatments is the use of micellar viscoelastic non-polymer acids. The reagent, allowing to obtain effective diverter slug units on the basis of hydrochloric acid of low concentration of 3-5%, was tested. The possibility to obtain self-diverting acid using the reagent was demonstrated. The rheological properties of the reagent (non-polymer diverter) are presented and excellent compatibility of the composition with the oils by the standard of Rosneft Oil Company is shown.

The technology for a well treatment with the use of viscoelastic diverter was tested in seven wells at the fields in Western Siberia. A permeability of terrigenous reservoir ranged from 0.5·10-3 to 0.001 mm2 and hydraulic fractures had extended perforation intervals of more than 6 m. The study of colmatant in proppant slug in case of Jurassic formations showed a significant content of calcite, iron compounds and silicon. All treatments with diverter were conducted using mud acids. A typical technology of well treatment is described. For five of seven wells with reservoir pressure below hydrostatic one, the appearance of excess head pressure in the course of treatment is noted. An average increase in initial well production rate was 6.3 t/day, an average increase of productivity index was more than twofold. The obtained values of the increments of oil production rate after the well treatment with non-polymer diverter are comparable with the efficiency of hydraulic fractures at a lower cost and a lower risk of increase of water production after the repair.
References
1. Economides J.M., Kenneth J.N., Reservoir stimulation, Houston: Wiley, 2002,
856 p.
2. Bulgakova G.T., Sharifullin A.R., Kharisov R.Ya. et al., Laboratory and theoretical
researches of matrix acid-based carbonates processing (In Russ.),
Neftyanoe khozyaystvo = Oil Industry, 2010, no. 5, pp. 75–79.
3. Kefi S., Expanding applications for viscoelastic surfactants, Oilfield Review,
2004, V. 16, no. 4, pp. 10–23.
4. Anderson V.J., Pearson J.R.A., Boek E.S., The rheology of worm-like micellar
fluids, Rheology Reviews, 2006, pp. 217–253.
5. Lin Z., Eads C.D., Polymer-induced structural transitions in oleate solutions:
microscopy, rheology, and nuclear magnetic resonance studies, Langmuir,
1997, V. 13, p. 2647.
6. Kern F., Lequeux F., Zana R., Canadau S.J., Dynamic properties of salt-free
viscoelastic micellar solutions, Langmuir, 1994, V. 10, p. 1714.

The heterogeneity of the reservoirs structure determines the complexity of a productive low-permeability formation processing due to high acid loss in the flushed zones. One of the ways to increase the efficiency of acid treatments is the use of micellar viscoelastic non-polymer acids. The reagent, allowing to obtain effective diverter slug units on the basis of hydrochloric acid of low concentration of 3-5%, was tested. The possibility to obtain self-diverting acid using the reagent was demonstrated. The rheological properties of the reagent (non-polymer diverter) are presented and excellent compatibility of the composition with the oils by the standard of Rosneft Oil Company is shown.

The technology for a well treatment with the use of viscoelastic diverter was tested in seven wells at the fields in Western Siberia. A permeability of terrigenous reservoir ranged from 0.5·10-3 to 0.001 mm2 and hydraulic fractures had extended perforation intervals of more than 6 m. The study of colmatant in proppant slug in case of Jurassic formations showed a significant content of calcite, iron compounds and silicon. All treatments with diverter were conducted using mud acids. A typical technology of well treatment is described. For five of seven wells with reservoir pressure below hydrostatic one, the appearance of excess head pressure in the course of treatment is noted. An average increase in initial well production rate was 6.3 t/day, an average increase of productivity index was more than twofold. The obtained values of the increments of oil production rate after the well treatment with non-polymer diverter are comparable with the efficiency of hydraulic fractures at a lower cost and a lower risk of increase of water production after the repair.
References
1. Economides J.M., Kenneth J.N., Reservoir stimulation, Houston: Wiley, 2002,
856 p.
2. Bulgakova G.T., Sharifullin A.R., Kharisov R.Ya. et al., Laboratory and theoretical
researches of matrix acid-based carbonates processing (In Russ.),
Neftyanoe khozyaystvo = Oil Industry, 2010, no. 5, pp. 75–79.
3. Kefi S., Expanding applications for viscoelastic surfactants, Oilfield Review,
2004, V. 16, no. 4, pp. 10–23.
4. Anderson V.J., Pearson J.R.A., Boek E.S., The rheology of worm-like micellar
fluids, Rheology Reviews, 2006, pp. 217–253.
5. Lin Z., Eads C.D., Polymer-induced structural transitions in oleate solutions:
microscopy, rheology, and nuclear magnetic resonance studies, Langmuir,
1997, V. 13, p. 2647.
6. Kern F., Lequeux F., Zana R., Canadau S.J., Dynamic properties of salt-free
viscoelastic micellar solutions, Langmuir, 1994, V. 10, p. 1714.


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