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Updating of limited bottomhole pressures for carbonate and sandstone reservoirs operated by Tatneft PJSC

UDK: 622.276.5.001.5
DOI: 10.24887/0028-2448-2019-7-36-39
Key words: rate transient analysis, inflow performance relationship (IPR) curve, limited pressure, production peak
Authors: V.A. Iktissanov (TatNIPIneft, RF, Bugulma), N.Kh. Musabirova (TatNIPIneft, RF, Bugulma), A.V. Baigushev (TatNIPIneft, RF, Bugulma), K.F. Shipilova (TatNIPIneft, RF, Bugulma)

Inflow performance relationship (IPR) shows a peak flow rate corresponding to the limited bottomhole pressure at significant flowing bottomhole pressure drop in producing wells. It follows that oil production can be improved if a well can be made to produce at a limited bottomhole pressure. So, the objective of the research was to upd ate data on limited bottomhole pressures in the main assets of Tatneft PJSC. The tests were carried out in 79 wells, including, 40 wells completed in the Devonian sandstone reservoirs, 19 wells in the Carboniferous sandstone reservoirs, and 20 wells in carbonate reservoirs. To ensure data reliability, pressure downhole gauges se t at formation tops were used in 64 wells. For the first time ever, measurements of limited bottomhole pressure were performed in eight horizontal wells. The research included determination of relationships between oil and fluid production rates and flowing bottomhole pressures (IPR curves) for all wells; we also considered deterioration of reservoir properties at pressure decrease and their improvement at pressure increase. The results of laborious and extensive tests suggest the following tendencies. Limited bottomhole pressures corresponding to peak production have been obtained in 83 % of wells; the remaining IPR curves have no production extremum. Generally, limited pressures and limited pressure-bubble point pressure relationships vary significantly, even within the same reservoir rock. This can, presumably, be accounted for varying physicochemical properties of oil, permeability to gas and oil, flow capacity, etc. No relationship between limited pressure and water cut within the same reservoir rock has been found; neither was determined any significant difference between limited pressures for fluid and oil production. The latter can be explained by relatively stable water cut profile. Decrease of the bottomhole pressure to the value of the limited pressure and even lower brings about decrease of well deliverability. The IPR curves with the recorded FBHP decrease and increase testify to incomplete permeability and porosity restoration once bottomhole pressure has increased following the period of well operation at low FBHP. It should be noted, however, that these variations are at the level of flowrate measurement error. It was found that the limited bottomhole pressures in horizontal wellbores are higher than in vertical wellbores. A possible explanation is that a larger area around the wellbore has been damaged because of gas coming out of solution in this area. On the whole, the carried out tests yielded valuable information, which will help the Company to improve the efficiency of oil production operations. The possible economic effect is estimated at a level of billion Russian rubles.

References

1. Muslimov R.Kh., Zaynullin N.G., Diyashev R.N., Zinnatov I.Kh., Justification of optimal bottomhole pressure for terrigenous reservoirs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 1984, no. 9, pp. 27–29.

2. Diyashev R.N., Sovmestnaya razrabotka neftyanykh plastov (Joint development of oil reservoirs), Moscow: Nedra Publ., 1984, 207 p.

3. Mishchenko I.T., Skvazhinnaya dobycha nefti (Oil production), Moscow: Neft’ i gaz Publ., 2015, 448 p.

4. Vogel J.V., Inflow performance relationships for solution gas drive wells, Journal of Petroleum Technology, 1968, V. 20, no. 1, pp. 83–92, DOI: 10.2118/1476-PA.

5. Fetkovich M.J., The isochronal testing of oil wells, SPE 4529-MS, 1973, DOI: 10.2118/4529-MS.

6. Wiggins M.L., Generalized inflow performance relationships for three-phase flow, SPE 25458-MS, 1993, DOI: 10.2118/25458-MS.

7. Iktissanov V.A., Bobb I.F., Ganiev B.G., Study of the problem of optimization of bottomhole pressure for fractured-porous reservoirs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, Neftyanoe khozyaystvo, 2017, no. 10, pp. 94–97.

8. Iktissanov V.A., Patterns control the development of oil fields using optimization bottom-hole pressures for the porous collector (In Russ.), Burenie i neft', 2017, no. 3, pp. 14–18.

Inflow performance relationship (IPR) shows a peak flow rate corresponding to the limited bottomhole pressure at significant flowing bottomhole pressure drop in producing wells. It follows that oil production can be improved if a well can be made to produce at a limited bottomhole pressure. So, the objective of the research was to upd ate data on limited bottomhole pressures in the main assets of Tatneft PJSC. The tests were carried out in 79 wells, including, 40 wells completed in the Devonian sandstone reservoirs, 19 wells in the Carboniferous sandstone reservoirs, and 20 wells in carbonate reservoirs. To ensure data reliability, pressure downhole gauges se t at formation tops were used in 64 wells. For the first time ever, measurements of limited bottomhole pressure were performed in eight horizontal wells. The research included determination of relationships between oil and fluid production rates and flowing bottomhole pressures (IPR curves) for all wells; we also considered deterioration of reservoir properties at pressure decrease and their improvement at pressure increase. The results of laborious and extensive tests suggest the following tendencies. Limited bottomhole pressures corresponding to peak production have been obtained in 83 % of wells; the remaining IPR curves have no production extremum. Generally, limited pressures and limited pressure-bubble point pressure relationships vary significantly, even within the same reservoir rock. This can, presumably, be accounted for varying physicochemical properties of oil, permeability to gas and oil, flow capacity, etc. No relationship between limited pressure and water cut within the same reservoir rock has been found; neither was determined any significant difference between limited pressures for fluid and oil production. The latter can be explained by relatively stable water cut profile. Decrease of the bottomhole pressure to the value of the limited pressure and even lower brings about decrease of well deliverability. The IPR curves with the recorded FBHP decrease and increase testify to incomplete permeability and porosity restoration once bottomhole pressure has increased following the period of well operation at low FBHP. It should be noted, however, that these variations are at the level of flowrate measurement error. It was found that the limited bottomhole pressures in horizontal wellbores are higher than in vertical wellbores. A possible explanation is that a larger area around the wellbore has been damaged because of gas coming out of solution in this area. On the whole, the carried out tests yielded valuable information, which will help the Company to improve the efficiency of oil production operations. The possible economic effect is estimated at a level of billion Russian rubles.

References

1. Muslimov R.Kh., Zaynullin N.G., Diyashev R.N., Zinnatov I.Kh., Justification of optimal bottomhole pressure for terrigenous reservoirs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 1984, no. 9, pp. 27–29.

2. Diyashev R.N., Sovmestnaya razrabotka neftyanykh plastov (Joint development of oil reservoirs), Moscow: Nedra Publ., 1984, 207 p.

3. Mishchenko I.T., Skvazhinnaya dobycha nefti (Oil production), Moscow: Neft’ i gaz Publ., 2015, 448 p.

4. Vogel J.V., Inflow performance relationships for solution gas drive wells, Journal of Petroleum Technology, 1968, V. 20, no. 1, pp. 83–92, DOI: 10.2118/1476-PA.

5. Fetkovich M.J., The isochronal testing of oil wells, SPE 4529-MS, 1973, DOI: 10.2118/4529-MS.

6. Wiggins M.L., Generalized inflow performance relationships for three-phase flow, SPE 25458-MS, 1993, DOI: 10.2118/25458-MS.

7. Iktissanov V.A., Bobb I.F., Ganiev B.G., Study of the problem of optimization of bottomhole pressure for fractured-porous reservoirs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, Neftyanoe khozyaystvo, 2017, no. 10, pp. 94–97.

8. Iktissanov V.A., Patterns control the development of oil fields using optimization bottom-hole pressures for the porous collector (In Russ.), Burenie i neft', 2017, no. 3, pp. 14–18.


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