Q Estimation from VSP Data and Applying Inverse Q-filtering in Processing of Surface 3D Seismic Data

Previous studies performed in Abu Dhabi oilfields, United Arab Emirates, revealed the direct link of seismic wave attenuation to petrophysical properties of rocks. However, all those studies were based on zero offset VSP data, which limits the attenuation estimation at one location only. This is due to the difficulty of estimating attenuation from 3D seismic data, especially in carbonate rocks. To overcome this difficulty, we developed a workflow based on the centroid frequency shift method and Gabor transform which is optimized by using VSP data. The workflow was applied on 3D Ocean Bottom Cable seismic data. Distinct attenuation anomalies were observed in highly heterogeneous and saturated zones, such as the reservoirs and aquifers. Scattering shows significant contribution in attenuation anomalies, which is unusual in sandstones. This is due to the complex texture and heterogeneous nature of carbonate rocks. Furthermore, attenuation mechanisms such as frictional relative movement between fluids and solid grains, are most likely other important causes of attenuation anomalies. The slight lateral variation of attenuation reflects the lateral homogeneous stratigraphy of the oilfield. The results demonstrate the potential of seismic wave attenuation for delineating heterogeneous zones with high fluid content, which can substantially help for enhancing oil recovery.

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Geological structure of the Khylly field according to 3D seismic data

News of the Ural State Mining University ◽

10.21440/2307-2091-2020-3-52-61 ◽

2020 ◽

Vol 59 (3) ◽

pp. 52-61

Author(s):

Tofik Rashid ogly AKHMEDOV ◽

◽

Aigyun Nemat kyzy SULTANOVA ◽

Keyword(s):

Seismic Data ◽

Oil And Gas ◽

Velocity Model ◽

Geological Structure ◽

Seismic Survey ◽

Main Task ◽

Velocity Analysis ◽

3D Seismic ◽

Vsp Data ◽

3D Seismic Data

Relevance of the work. The paper considers challenging problems related with outlining of intervals with oil and gas presence in the mature Khylly field by use of latest 3D seismic survey techniques in order to gain larger crude resources base. The purpose of this research is to discover the most promising intervals of target horizons with relatively high reservoir properties outlined by 3D seismic data. The subjects of research are 3D seismic survey data, downhole seismic survey – Vertical Seismic Profiling (VSP) and well logging diagrams. The object of research is the Khylly deposit. The paper describes in brief geological and geophysical characteristics, stratigraphic and lithological features of rocks making the section. It is noted that despite repeated surveys by use of various geological and geophysical techniques, the field setting is not thoroughly studied and it has been covered by 3D seismic survey in 2012. Research results. 3D seismic survey applied across Khylly area is resulted in drawing of 4 structural maps for III and I horizons of Productive Series (PS), Akchagyl and Lower Absheron suites. Taking into account the relevance of structural planes of various stratigraphic levels and III horizon of PS being one of the major reference horizons the paper gives description of structural map drawn for this horizon. The detailed velocity model is designed based on VSP data with wide use of velocity analysis data. It has been made clear that Khylly area has block structure and each block has been described in detail. Based on acquired data it has been recommended to drill exploratory well R-1. Conclusion. Processing and interpretation of seismic data are aimed at solving some geological problems; the main task was to obtain results that ensure the study of the geological structure in the seismic survey area, including tracing of seismic horizons, faults and outlining the areas and section intervals which may be of interest due to possible oil and gas presence. VSP data acquired in well 2012 and velocity analysis made it possible to design velocity model of the section under the study, with the use of which the temporary 3D cube was transformed into a depth cube. The quality of seismic data is good and made it possible to solve the tasks set for this research.

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