The authors introduce a new method of oil wells stimulation for carbonate reservoirs, characterized by the presence of a gas cap or adjacent water-bearing interlayers has been tested. This method is based on combination of mechanical (radial drilling using special technical system) and chemical (acid treatment of channels) methods. The technical system provides for application of radial mechanical drilling technology with the use of a special small-sized screw downhole motor. The main advantages of the technology, as compared with standard methods of perforation, are the possibility of selective action on the formation due to the predicted route of the channel and multiple placing of reagents and logging tools to the channel. The novelty of the technology lies in selective directional treatment, which allows effectively overcome the critical matrix zone and restore well productivity after drilling fluid infiltration. The ability to predict the trajectory of the channels while drilling makes it possible to avoid contact with water-saturated interlayers. This technology was first tested during works on recompletion in the overlying carbonate reservoirs of Kashirskian-Podolskian deposits of Arlanskoye field and Bashkirian stage deposits of Yugomashevskoye fields, operated by Bashneft-Dobycha LLC. The formations are characterized by the high heterogeneity and relatively close location of water-saturated interlayers. Three wells were selected for field testing. Two channels were drilled in each well: in two wells 7 m in length, in the third well 14 m. After drilling the channels, acidizing was performed through a special jet nozzle. More than 10 m3 of hydrochloric acid composition was injected into each of the drilled channels. Oil flow rate after field tests was 1.5 t/day in the first well, 3.9 t/day in the second one and 40.5 t/day in the third one. The experience of combining radial drilling of channels and acid treatment showed a number of advantages: first, the possibility of commingling formation zones separated by low-permeability vertical barriers; second, reduction of risks of breakthrough into water-bearing formations.
1. Loginov B.G., Malyshev L.G., Garifullin Sh.S., Rukovodstvo po kislotnym obrabotkam skvazhin (Guide to acid treatment of wells), Moscow: Nedra Publ., 1966, 219 p.
2. Suchkov B.M., Intensifikatsiya raboty skvazhin (Well stimulation), Moscow - Izhevsk: Publ. of Institute for Computer Research, 2007, 612 p.
3. Shaydullin V.A., Kamaletdinova R.M., Yakupov R.F. et al., Selecting the water shut-off technology for monolithic terrigenous formations (In Russ.), Neft’. Gaz. Novatsii, 2021, no. 7, pp. 34–38.
4. Patent US6772847B2, Chemically enhanced drilling methods, Inventors: Rae Philip J., Di Lullo Arias, Gino F., Portman, Lance N.
5. Rae Ph., Di Lullo G., Chemically-enhanced drilling with coiled tubing in carbonate reservoirs, SPE-67830-MS, 2001, DOI: https://doi.org/10.2118/67830-MS
6. Portman L., Rae Ph., Munir A., Full-scale tests prove it practical to «drill» holes with coiled tubing using only acid; no motors, no bits, SPE-74824-MS, 2002, DOI: https://doi.org/10.2118/74824-MS
7. Stanley F.O., Portman L.N., Diaz J.D. et al., Global application of coiled-tubing acid tunneling yields effective carbonate stimulation, SPE-135604-MS, 2010, DOI: https://doi.org/10.2118/135604-MS
8. Moss P., Portman L., Rae Ph., di Lullo G., Nature had it right after all! Constructing a “Plant Root”-like drainage system with multiple branches and uninhibited communication with pores and natural fractures, SPE-103333-MS, 2006, DOI: https://doi.org/10.2118/103333-MS
9. Perex L.A.A., Diaz J.D., Navarro M. et al., Successful offshore application of acid tunneling technology: Overcoming the difficulties of high depths, temperatures, and deviations, SPE-113855-MS, 2008, DOI: https://doi.org/10.2118/113855-MS
10. Diaz J.D., Espina V., Guerrero M. et al., Successful implementation of coiled-tubing acid tunneling gives operator a viable alternative to conventional stimulation techniques in carbonate reservoirs, SPE-107084-MS, 2007, DOI: https://doi.org/10.2118/107084-MS
11. Akhkubekov A.E., Vasilyev V.N., Acid tunneling technology: Application potential in Timan-Pechora carbonates, SPE-135989-MS, 2010, DOI: https://doi.org/10.2118/135989-MS
12. Strasburg J., Clark J., Acid tunneling stimulation in Oklahoma limestone using coiled tubing, SPE-120772-MS, 2009, DOI: https://doi.org/10.2118/120772-MS
13. Lyagov I.A., Baldenko F.D., Lyagov A.V. et al., Methodology for calculating technical efficiency of power sections in small-sized screw downhole motors for the “Perfobur” system (In Russ.), Zapiski Gornogo instituta, 2019, no. 6, pp. 694-700, DOI: https://doi.org/10.31897/pmi.2019.6.694
14. Basniev K.S., Kochina I.N., Maksimov V.M., Podzemnaya gidromekhanika (Underground hydromechanics), Moscow: Nedra Publ., 1993, 416 p.15.