Carbonate reservoirs worldwide are the main oil production resources due to their large scale and wide spread. One of the challenges in the carbonates development is increasing waterflooding efficiency. This paper considers the issue of a water loss to an underlying aquifer through the fractures in non porous carbonates that open at a high water injection pressure. The results of the field data analysis allow suggesting that carbonate rocks are fractured under conditions of waterflooding. These fractures may cause a loss of injected water. Consequently, the oil recovery efficiency may also decrease. In order to solve this problem in the oilfields of the Republic of Bashkortostan, the water loss percentage was calculated using a material balance analysis. Also, a conceptual model of a fluid flow during a waterflooding of the tournaisian carbonate reservoir of Tujmazinskoe oilfield was proposed. On the basis of this model an algorithm of the water loss estimation was developed. The new algorithm takes into account the results of well testing and a variation of geological parameters, and can increase the accuracy of calculations for the carbonate reservoirs with uncertainties in the aquifer influx and a flow behind casing. The results of this research could be used to estimate injection rates for carbonate reservoirs of the oilfields of the Republic of Bashkortostan in the conditions of water loss to an underlying aquifer.
References
1. Carbonate reservoirs – Overcome challenging heterogeneity, URL: https://www.slb.com/technical-challenges/carbonates#related-information.
2. Yakupov R.F., Mukhametshin V.Sh., Problem of efficiency of low-productivity carbonate reservoir development on example of Turnaisian stage of Tuymazinskoye field (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 12, pp. 106–110.
3. Akbar M. et al., A snapshot of carbonate reservoir evaluation, Oilfield Review, 2000, V. 12, no. 4, pp. 20–41.
4. Zheng-Xiao Xu et al., A review of development methods and EOR technologies for carbonate reservoirs, Petroleum Science, 2020, V. 17, no. 4, pp. 990–1013,
DOI: https://doi.org/10.1007/s12182-020-00467-5
5. Akhmetzyanov R.R. et al., How to increase the efficiency of the reservoir pressure maintenance system during field development (In Russ.), Territoriya Neftegaz, 2015, no. 2, pp. 14–17.
6. Dake L.P., The practice of reservoir engineering, Elsevier, 2001, 572 p.
7. Prilozhenie 13 k instruktsii PAO “NK “Rosneft’” (Appendix 13 to the instructions of Rosneft PJSC), Rukovodstvo pol’zovatelya informatsionnoy sistemy “Kompleks instrumentov dlya neftyanogo inzhiniringa” (User’s guide for the Information System “Complex of Tools for Petroleum Engineering”), Modul’ material’nyy balans (Material balance module). Ver. 2.0, Moscow: Publ. of Rosneft Oil Company, 2020. – 26 p.
