17 offshore oilfields of Azerbaijan have been being developed for a long period of time within the Caspian shelf. 400 mln.t of oil has been produced during that period, what corresponds to the current average oil recovery of 0.33. Wellsite data analysis of these oilfields identifies wide discrepancy in oilfield development outcomes, whereas identical production techniques had been employed ubiquitously: current oil recovery factor varies from 0.05 to 0.60 for the Absheron archipelago and from 0.08 to 0.30 for the Baku archipelago.
Revealing factors, that impact oil recovery and, thereby, justifying measures for further efficient development of the oilfields is of keen scientific and practical interest. It is well-known that such a problem is reliably solved based on geological mathematical models, since interpretation of their structure facilitates revealing the role of natural technological parameters of oilfields during production. Nevertheless, building an oil recovery model for the entire region without manifestation features of oilfield drive conditions being taken into account turns out to be incorrect.
Two types of formation drives can be distinguished in a majority of the oilfields of the South Caspian depression: active and passive.
Passive type featuring solution gas drive (as formation pressure drops during the development process oil gives off dissolved gas, by virtue of which oil is displaced towards a well drainage area at low rates).
Active type is characterized by combination drive (shows as energy of water bodies of perimeter areas in combination with solution gas drive).
After detailed study of manifestation features of the oil pool formation drives of the offshore oilfields using mathematical methods (cluster analysis, discriminant functions etc.), the following layout has been revealed: 68 production units are characterized by solution gas drive, 81 units -- by combination drive.
Based on development outcomes, identified oil pool types distinguish considerably from one another. Thus, current average oil recovery factor for group I oil pools is 0.20, whereas for group II units –more than 0.38.
In order to find out diverse production reasons oil recovery models have been built in selected pool groups.
It should be noted that only those factors, that had considerable impact upon oil recovery, have been incorporated into the equation structure. The paper covers brief interpretation of acquired models and graphic representation of impact of geological and technological factors on oil recovery.
Analysis of models, built to reveal the role of formation parameters during development of oilfields grouped according to drives, enabled unscrambling the features of oil recovery process for the Azerbaijan offshore fields. Based on produced results it is possible to justify measures on optimization oil recovery dynamics from Azerbaijan offshore oilfields.
References
1. Bagirov B.A., Salmanov A.M., Gasanaliev M.K., Nazarova S.A., On certain
categories of oil reserves (In Russ.), Geologiya nefti i gaza = The journal Oil and
Gas Geology, 1998, no. 1, pp. 22–25.
2. Bagirov B.A., Neftegazopromyslovaya geologiya (Oil and gas geology),
Baku: Publ. of ASPA, 2011, 311 p.
3. Abdullaeva L.A., The reason for the varying results of offshore fields development
(In Russ.), Geolog Azerbaydzhana, 2006, no. 11, pp. 105–110.
