Case Study: Complex Marginal Oil Field Modeling - Fast Transition From Exploration to Development
- Vuk Kalinic (STC NIS Naftagas) | Evgenia Milei (STC NIS Naftagas) | Ivan Al-Jeboore (STC NIS Naftagas)
- Document ID
- Society of Petroleum Engineers
- SPE Europec featured at 81st EAGE Conference and Exhibition, 3-6 June, London, England, UK
- Publication Date
- Document Type
- Conference Paper
- 2019. Society of Petroleum Engineers
- proluvial fans, green field modeling, multidisciplinary approach, recovery factor estimate, vertical and lateral heterogeneity
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- 54 since 2007
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As active oil reservoirs mature, marginal fields development and management is becoming increasingly important.
Early identification of high degree reservoir heterogeneity served as starting point for an in-depth analysis for both, geologist and reservoir engineer.
This paper describes complex approach applied during evaluation and development of marginal oil field "Is" located in Serbia (Pannonian Basin).
Effective transition from exploration to development took place in 3 stages.
I-stage: 1 exploration well drilled, detailed analysis (seismic, sedimentology, core, PVT) and interpretation (log, well-test). Identification of vertical heterogeneity led to detailed analysis, which resulted in local depositional environment theory. Integration of seismic attribute and sedimentological analysis results was done. Due to geological uncertainties several 3D models were done for STOIIP range estimation. Recovery factor range was estimated using statistical, analytical and simulation model approach.
II-stage: 1 exploration well and 1 development well drilling and detailed analysis update.
III-stage: drilling of 5 development wells and continuous update of geological and simulation models.
Major uncertainties identified during I-stage were regarding to: reservoir structure, vertical and lateral heterogeneity, major fault permeability and OWC depth. Additionally, existence of active aquifer affected recovery factor estimation range.
I-stage analysis showed that, depending on depositional environment 4 different rock types are presented by conglomerates, conglo-breccia, breccia and metamorphic rocks.
The target formation (conglomerates) were formed by proluvial fan. This deposits are characterized by an alternation of rhythms (fragment size and orientation, conglomerate size, terrigenous material sorting).
Proluvial fan boundaries were detected on the seismic attribute map.
Second exploration well location was a result of multidisciplinary analysis during I-stage. Well was successful and highly informative during II-stage as it proved oil saturation behind major fault, reduced previous STOIIP estimates and confirmed presence of active aquifer.
STOIIP and reservoir structure excluded possibilities for regular/typical well patterns, therefore each well location was carefully selected, while total well number was determined based on estimated recovery factor.
Complex multidisciplinary approach used during this project, can be an example for successful and effective marginal heterogeneous oil field development. Understanding the reasons for reservoir heterogeneity together with confident estimate of recovery factor, gave us success during each new well placement and total well number determination.
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