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Conceptual model to highlight oil reserves of different quality by area: the case of Vietnam’s offshore greenfield study

UDK: 553.98(2/.9)
DOI: 10.24887/0028-2448-2020-8-27-29
Key words: conceptual model, Vietnam offshore, properties trend, static model, lateral reserves distribution, netpay forecast, erosion processes, tectonics, Oligocene, seismic interpretation
Authors: A.G. Chvertkov (VNIIneft JSC, RF, Moscow), T.S. Baranov (VNIIneft JSC, RF, Moscow), G.D. Fedorchenko (Zarubezhneft JSC, RF, Moscow)
Beluga oilfield locates in southern-eastern part of Cuulong basin Vietnam offshore. Main reservoir is terregionious deposits of upper Oligocene. Initially, when designing the development of the field, a geological model was built based on the results of drilling two exploratory wells. Based on this model, geological reserves were calculated, well placement was planned, and a field production profile was built. However, when drilling with production wells, a number of problems were identified, such as the lack of confirmation of effective thicknesses, as a result, lower initial parameters compared to the plan and high rates of their decline.
Based on re-processing and re-interpretation of seismic data, a new concept of the geological structure of the Beluga field is proposed. In accordance with the new concept, the change in effective oil-saturated thicknesses is due to a change in the total thickness, which is associated with a degradation of upper part of the productive complex due to the high tectonic activity of this region. New conceptual depo-tectonic and static model developed through new seismic reprocessing and geological interpretation explains drastically netpay and reservoir properties lateral changing. That is also confirmed by different starting well rates. Zones of various geological structures are distinguished, which differ in characteristic thicknesses and reservoir properties. Separately, reserves were calculated for each zone and the zones were ranked depending on the quality of the collector. The allocation of zones with reserves of different quality is the basis for choosing the optimal development systems for each field site.
References
1. Galimova A.F., Afanas'ev I.S., Baranov T.S. et al., Miocene and Oligocene under conditions of geological underdevelopment, the Beluga field, Vietnam (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 9, pp. 34–39.
2. Shoup R.C., Morley R.J., Swiecicki T., Clark S., Tectono-stratigraphic framework and tertiary paleogeography of southeast Asia: Gulf of Thailand to South Vietnam shelf, URL: http://www.searchanddiscovery.com/pdfz/documents/2012/30246shoup/ndx_shoup.pdf.html
3. Obobshchenie i analiz geologo-geofizicheskikh materialov severnoy i severo-vostochnoy chastey mestorozhdeniya Belyy Tigr s tsel'yu vyyavleniya nestrukturnykh lovushek UV (Generalization and analysis of geological and geophysical materials of the northern and northeastern parts of the White Tiger field in order to identify non-structural hydrocarbon traps), Hanoi: Publ. of VPI, 2014.
4. Zoback M., Reservoir geomechanics, New York: Cambridge University Press, 2007, 449 p.
Beluga oilfield locates in southern-eastern part of Cuulong basin Vietnam offshore. Main reservoir is terregionious deposits of upper Oligocene. Initially, when designing the development of the field, a geological model was built based on the results of drilling two exploratory wells. Based on this model, geological reserves were calculated, well placement was planned, and a field production profile was built. However, when drilling with production wells, a number of problems were identified, such as the lack of confirmation of effective thicknesses, as a result, lower initial parameters compared to the plan and high rates of their decline.
Based on re-processing and re-interpretation of seismic data, a new concept of the geological structure of the Beluga field is proposed. In accordance with the new concept, the change in effective oil-saturated thicknesses is due to a change in the total thickness, which is associated with a degradation of upper part of the productive complex due to the high tectonic activity of this region. New conceptual depo-tectonic and static model developed through new seismic reprocessing and geological interpretation explains drastically netpay and reservoir properties lateral changing. That is also confirmed by different starting well rates. Zones of various geological structures are distinguished, which differ in characteristic thicknesses and reservoir properties. Separately, reserves were calculated for each zone and the zones were ranked depending on the quality of the collector. The allocation of zones with reserves of different quality is the basis for choosing the optimal development systems for each field site.
References
1. Galimova A.F., Afanas'ev I.S., Baranov T.S. et al., Miocene and Oligocene under conditions of geological underdevelopment, the Beluga field, Vietnam (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 9, pp. 34–39.
2. Shoup R.C., Morley R.J., Swiecicki T., Clark S., Tectono-stratigraphic framework and tertiary paleogeography of southeast Asia: Gulf of Thailand to South Vietnam shelf, URL: http://www.searchanddiscovery.com/pdfz/documents/2012/30246shoup/ndx_shoup.pdf.html
3. Obobshchenie i analiz geologo-geofizicheskikh materialov severnoy i severo-vostochnoy chastey mestorozhdeniya Belyy Tigr s tsel'yu vyyavleniya nestrukturnykh lovushek UV (Generalization and analysis of geological and geophysical materials of the northern and northeastern parts of the White Tiger field in order to identify non-structural hydrocarbon traps), Hanoi: Publ. of VPI, 2014.
4. Zoback M., Reservoir geomechanics, New York: Cambridge University Press, 2007, 449 p.


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