When saline reservoirs are flooded with low-mineralized water in the near-well zone of producing wells, conditions may arise for intra-reservoir precipitation of solid salt sediment NaCl, which leads to colmatation of the pore space, reducing the permeability and productivity of wells. The effects of self-colmatation due to the precipitation of NaCl salt sediment in the pore space during flooding of salinized strata with low-salinity water is characteristic of a number reservoirs in Eastern Siberia. A mathematical model is proposed that allows us to calculate the technogenic change in reservoir permeability due to the deposition of solid NaCl particles, initiated by the effect of oversaturation of the filtered salt solution due to water evaporation at the border with the gas phase when the pressure decreases below the saturation pressure in the oil-gas system. It is shown that the intense precipitation of solid salt sediment and the corresponding damage of the reservoir permeability occur at a distance of ~ 1 m from the borehole wall. In the remote part of the near-wellbore zone and in the interwell space, the influence of this process on filtration flows in the formation can be neglected. Calculated model dependences of the dynamics of changes in the normalized permeability on the wellbore wall and the skin factor at different values of the reaction rate of the formation of solid sediment from a salt solution are obtained. The results of the assessment of the parameters of the technologically damage near-wellbore zone are basic information for the preparation of designs of effective geological and technological measures to restore the productivity of wells. In particular, they allow determining the optimal volume for flushing the near-wellbore zone with fresh water and correctly planning the timing of its implementation.
1. Vinogradov I.A., Zagorovskiy A.A., Grinchenko V.A., Gordeev Ya.I., Investigation of desalination process in the development of saline clastic reservoirs of Verkhnechonskoye field (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 1, pp. 74–77.
2. Kashchavtsev V.E., Mishchenko I.T., Soleobrazovanie pri dobyche nefti (Salt formation in oil production), Moscow: Orbita-M Publ., 2004, 432 p.
3. Chertovskikh E.O., Alekseev S.V., Problems of oil and gas production associated with gypsum depositing in the Verkhnechonskoye oil and gas condensate field (In Russ.), SPE-171311-RU, 2014.
4. Tsypkin G.G., Techeniya s fazovymi perekhodami v poristykh sredakh (Phase transition flows in porous media), Moscow: FIZMATLIT, 2009, 232 p.
5. Gaydukov L.A., Nikolaev V.A., Vorob'ev V.S., Features of water and process fluids effect on filtration properties of terrigenous reservoirs of the Nepa suite of Eastern Siberia, SPE-187880-MS, 2017, https://doi.org/10.2118/187880-MS
6. Petrushevskiy E.I., Evaporation of residual water in gas strata during isothermal filtration (In Russ.), Izvestiya vuzov, 1965, no. 11, pp. 22–25.
7. Verigin N.N., Sherzhukov B.S., Diffuziya i massoobmen pri fil'tratsii zhidkostey v poristykh sredakh (Diffusion and mass transfer in liquid filtration in porous media), In: Razvitie issledovaniy po teorii fil'tratsii v SSSR (Development of researches on the theory of filtration in the USSR), Moscow: Nauka Publ., 1966, pp. 237-313.
8. Bogdanov A.V., Ismayilov T.A., Estimation of dissolution velocity for halite in open volume and in porous medium (In Russ.), Vesti gazovoy nauki, 2017, no. 2 (30), pp. 208–213.
9. Grinchenko V.A., Povyshenie effektivnosti razrabotki zapasov nefti v zasolonennykh kollektorakh (Improving the efficiency of developing oil reserves in saline reservoirs): thesis of candidate of technical science, Tyumen, 2013.