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Development of formulation of hydrophobic emulsion for selective acidizing of fractured-cavernous carbonate reservoirs

UDK: 622.276.63
DOI: 10.24887/0028-2448-2017-11-129-131
Key words: acidizing, selective mechanism, drainage wellbore zone, hydrophobic emulsion, physical properties, viscosity, yield point, voltage stability, dispersed phase, dispersed environment
Authors: N.G. Ibragimov (Tatneft PJSC, RF, Almetyevsk), M.Kh. Musabirov, A.Yu. Dmitrieva (TatNIPIneft, RF, Bugulma)

Maintaining sustainable oil production is possible, largely, due to successful application of technologies for wellbore zone treatment, in particular, selective acidizing of carbonate reservoirs. Reservoir heterogeneity results in poor conformance, uneven distribution of displacement agent, and, consequently, forming of flushed zones with low flow coefficients. This leads to increased water production and higher water cut of produced oil, while, low-permeability layers remain underproduced, or even bypassed. Selective acidizing of productive layers might be a good solution in this case. The mechanism of selective acidizing is based on temporary blocking of flushed (fractured) intervals with some high-viscosity system (a kind of “liquid plug”) inert to acid and solved with oil while production. High-concentration hydrophobic water-in-oil emulsions meet these requirements to the point. They are characterized by a wide range of viscosity control, fr om few dozens of centipoise to dozens of thousands of centipoise, up to non-flowing, as well as by controllable physical properties, including yield point (static and dynamic shear stress), thixotropic properties (structure strengthening with time), non-Newtonian rheology (pseudoplastic and/or viscoelastic flow).

This paper presents results of studies aimed at development of special formulations of high-concentration hydrophobic emulsions to be used in challenging conditions of fractured-cavernous reservoirs, wh ere conventional hydrophobic emulsions fail to block permeable zones and direct acid systems to target intervals. The designed formulation of  high-concentration hydrophobic emulsion provides for enhanced blocking properties needed to redirect the injected acid systems from the fractured (and, as a rule, water-saturated) zones to oil-saturated matrix zones, high-performance killing of wells during workover operations, and enhanced water shutoff properties, resulting in overall cost saving.

References

1. Musabirov M.Kh., Sokhranenie i uvelichenie produktivnosti neftyanykh plastov (Preserving and increasing the productivity of oil reservoirs), Kazan’: FEN Publ., 2007, 424 p.

2. Orlov G.A., Musabirov M.Kh., Ispol'zovanie osobennostey reologofil'tratsionnykh svoystv kontsentrirovannykh obratnykh emul'siy dlya napravlennogo fiziko-khimicheskogo vozdeystviya na plast (Using the rheology-filtering properties of concentrated reverse emulsions for directed physicochemical effect on the formation), Collected papers “Problemy kompleksnogo osvoeniya trudnoizvlekaemykh zapasov nefti i prirodnykh bitumov (dobycha i pererabotka)” (Problems of integrated development of hard-to-recover oil and natural bitumen reserves (mining and processing)), Part 2 “Neft' i bitumy” (Oil and bitumen), Proceedings of International Conference, 1994, pp. 657–662.

3. Musabirov M.Kh., Razrabotka kompleksa tekhnologiy sokhraneniya i uvelicheniya produktivnosti pri vskrytii i ekspluatatsii neftyanykh plastov (Development of a complex of technologies for conservation and increase in productivity in the completion of a well and operation of oil reservoirs): thesis of doctor of technical science, Bugul'ma, 2007.

4. Mirzadzhanzade A.Kh., Reologicheskie problemy neftegazootdachi (Rheological problems of oil and gas recovery), Moscow: Publ. of VNIIOENG, 1986, 51 p.

5. Glushchenko V.N., Silin M.A., Neftepromyslovaya khimiya (Oilfield chemistry), Part 4. Kislotnaya obrabotka skvazhin (Well acidizing), edited by Mishchenko I.T., Moscow: Interkontakt Nauka Publ., 2010, pp. 607–624.

6. Orlov G.A., Kendis M.Sh., Glushchenko V.N., Primenenie obratnykh emul'siy v neftedobyche (Application of inverse emulsions in oil production), Moscow: Nedra Publ., 1991, 225 p.

7. Glushchenko V.N., Obratnye emul'sii i suspenzii v neftegazovoy promyshlennosti (Inverse emulsions and suspensions in the oil and gas industry), Moscow: Interkontakt Nauka Publ., 2008, 725 p.

Maintaining sustainable oil production is possible, largely, due to successful application of technologies for wellbore zone treatment, in particular, selective acidizing of carbonate reservoirs. Reservoir heterogeneity results in poor conformance, uneven distribution of displacement agent, and, consequently, forming of flushed zones with low flow coefficients. This leads to increased water production and higher water cut of produced oil, while, low-permeability layers remain underproduced, or even bypassed. Selective acidizing of productive layers might be a good solution in this case. The mechanism of selective acidizing is based on temporary blocking of flushed (fractured) intervals with some high-viscosity system (a kind of “liquid plug”) inert to acid and solved with oil while production. High-concentration hydrophobic water-in-oil emulsions meet these requirements to the point. They are characterized by a wide range of viscosity control, fr om few dozens of centipoise to dozens of thousands of centipoise, up to non-flowing, as well as by controllable physical properties, including yield point (static and dynamic shear stress), thixotropic properties (structure strengthening with time), non-Newtonian rheology (pseudoplastic and/or viscoelastic flow).

This paper presents results of studies aimed at development of special formulations of high-concentration hydrophobic emulsions to be used in challenging conditions of fractured-cavernous reservoirs, wh ere conventional hydrophobic emulsions fail to block permeable zones and direct acid systems to target intervals. The designed formulation of  high-concentration hydrophobic emulsion provides for enhanced blocking properties needed to redirect the injected acid systems from the fractured (and, as a rule, water-saturated) zones to oil-saturated matrix zones, high-performance killing of wells during workover operations, and enhanced water shutoff properties, resulting in overall cost saving.

References

1. Musabirov M.Kh., Sokhranenie i uvelichenie produktivnosti neftyanykh plastov (Preserving and increasing the productivity of oil reservoirs), Kazan’: FEN Publ., 2007, 424 p.

2. Orlov G.A., Musabirov M.Kh., Ispol'zovanie osobennostey reologofil'tratsionnykh svoystv kontsentrirovannykh obratnykh emul'siy dlya napravlennogo fiziko-khimicheskogo vozdeystviya na plast (Using the rheology-filtering properties of concentrated reverse emulsions for directed physicochemical effect on the formation), Collected papers “Problemy kompleksnogo osvoeniya trudnoizvlekaemykh zapasov nefti i prirodnykh bitumov (dobycha i pererabotka)” (Problems of integrated development of hard-to-recover oil and natural bitumen reserves (mining and processing)), Part 2 “Neft' i bitumy” (Oil and bitumen), Proceedings of International Conference, 1994, pp. 657–662.

3. Musabirov M.Kh., Razrabotka kompleksa tekhnologiy sokhraneniya i uvelicheniya produktivnosti pri vskrytii i ekspluatatsii neftyanykh plastov (Development of a complex of technologies for conservation and increase in productivity in the completion of a well and operation of oil reservoirs): thesis of doctor of technical science, Bugul'ma, 2007.

4. Mirzadzhanzade A.Kh., Reologicheskie problemy neftegazootdachi (Rheological problems of oil and gas recovery), Moscow: Publ. of VNIIOENG, 1986, 51 p.

5. Glushchenko V.N., Silin M.A., Neftepromyslovaya khimiya (Oilfield chemistry), Part 4. Kislotnaya obrabotka skvazhin (Well acidizing), edited by Mishchenko I.T., Moscow: Interkontakt Nauka Publ., 2010, pp. 607–624.

6. Orlov G.A., Kendis M.Sh., Glushchenko V.N., Primenenie obratnykh emul'siy v neftedobyche (Application of inverse emulsions in oil production), Moscow: Nedra Publ., 1991, 225 p.

7. Glushchenko V.N., Obratnye emul'sii i suspenzii v neftegazovoy promyshlennosti (Inverse emulsions and suspensions in the oil and gas industry), Moscow: Interkontakt Nauka Publ., 2008, 725 p.


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