Seismic & Quantitative Interpretation and Uncertainty Update, Example from Western Desert, Onshore Egypt
- Tanmay Mallick (Shell India Markets Private Limited) | Ashutosh Garg (Shell India Markets Private Limited) | Manish Choudhary (Shell India Markets Private Limited) | Saritha Nair (Shell India Markets Private Limited) | Sabyasachi Pal (Shell India Markets Private Limited) | Debadrita Jana (Shell India Markets Private Limited) | Abhinav Singh (Shell India Markets Private Limited) | Jeroen Goudswaard (Shell India Markets Private Limited) | Andrew Faulkner (Shell India Markets Private Limited) | Ravil Salakhetdinov (Shell India Markets Private Limited)
- Document ID
- Society of Petroleum Engineers
- SPE Middle East Oil & Gas Show and Conference, 6-9 March, Manama, Kingdom of Bahrain
- Publication Date
- Document Type
- Conference Paper
- 2017. Society of Petroleum Engineers
- 1.1 Well Planning, 7 Management and Information, 7.2.1 Risk, Uncertainty and Risk Assessment, 7.2 Risk Management and Decision-Making, 5.1.1 Exploration, Development, Structural Geology, 1.1 Well Planning, 5.1.2 Faults and Fracture Characterisation, 5 Reservoir Desciption & Dynamics, 5.1.8 Seismic Modelling, 5.1 Reservoir Characterisation, 1.6.6 Directional Drilling, 5.1.7 Seismic Processing and Interpretation
- Integration, Seismic, Quantitative, Uncertainty, Impedance
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A new seismic and quantitative reinterpretation was carried out for a brownfield in Western Desert, Egypt to improve depth predictability, de-risk appraisal well locations and to better understand producer-injector connectivity.
The study field is located in the Western Desert, Onshore Egypt and comprises of Upper Cretaceous tidal channel systems across four key reservoir levels where sand thicknesses range from 2 to 15 m. The field was discovered in 1993 but development drilling only commenced in 2008. The last integrated field study was performed in 2012. The analysis of wells drilled post-2012 indicated that there is a considerable depth difference along the flanks of the structure between seismic predicted depths and actual well tops (>50 m). The fault interpretation also required a re-look so as to reduce the lateral uncertainty of the main boundary fault and explain the lack of injection response in some areas of the field. This necessitated an update of seismic interpretation, static and dynamic models. A new interpretation could help identify attic volume upsides and help mature new appraisal and producer-injector locations. Further work was also proposed to test the feasibility of using seismic inversion for facies discrimination.
The available Pre-Stack Depth Migration (PreSDM) data was re-interpreted as part of the project. The fault interpretations were quality checked using Semblance/Dip maps, sand box models and wherever possible, were tied to the fault cuts seen in previously drilled wells. The time horizon correlation and seismic polarity were verified and were also cross-checked with the P-Impedance volume before being used in the static modelling workflow. The PreSDM Interval velocity model was used for depth conversion, where an anisotropy correction was applied to tie the wells. Vok and Polynomial methods were also applied, which in turn were used to derive depth uncertainty estimates. The update in the main bounding fault interpretation generated new appraisal locations in the deeper levels. The new interpretation was tested against the results from the latest drilling campaign in the field, and nine out of ten wells were within the one standard deviation uncertainty range.
Simultaneous inversion of the seismic data was also carried out as part of the project using the acoustic, shear and density data from 6 wells over the field. The inverted P-Impedance and S-Impedance were converted to Net to Gross (NtG), and were checked against the remaining 24 wells, which helped in validating the property cubes.
Forward wedge modelling suggested that individual sands of less than 15 m thickness would not be resolved from seismic due to seismic bandwidth limitations. Still, a review of inversion data together with geological insights and dynamic data helped to identify the high NtG areas across the reservoirs.
The integrated interpretation of inverted volumes with well and production data resulted in new insights into the field and helped to mature new appraisal and development well locations.
|File Size||22 MB||Number of Pages||11|
M. A. Wahdan, X. Le Varlet, A. Toukhy and H. A. El Rahman, "Planning the Subsurface Modeling Tool for the Full Field Life Cycle and Influences of Multi-Disciplinary Integration on Static Modeling: Examples from the Sitra field, Egyptian Western Desert, SPE 128100," in North Africa Technical Conference and Exhibition, Cairo, 2010.
M. K. Choudhary, A. Khandelwal, S. Nair, S. Pal, A. Munimandha, A. Kohli, S. Nirmohi, S. Gupta, S. Jain and R. Salakhetdinov, "Data Integration Helps in Identifying New Waterflood Opportunities in Western Desert, Onshore Field," in SPE Oil and Gas India Conference and Exhibition, Mumbai, April 2017.