The Seismic Interpretation for (X) Oil Field Depending on 3D Seismic Data of Nearby Oil Field, Southern Iraq.

This research focused on using seismic data to review the structure of the (X) Oil Field. The study utilises a 3D seismic survey conducted during 2011-2012, covering the (Y) Oil Field 2 km to the west


Study area
(X) Oil Field lies 2 km to the east of the (Y) Oil Field and about 5 km to the west of (Z) Oil Field [1].
It currently has 46 wells with a variety of data available [2]. The key wells of seismic area are Well-B and Well-D as they have more data, check shots data is available for Well-D. The data available for this study is outlined below in Table (1). Between January and August 2012, the first 3D seismic survey over the (Y) Oil Field was acquired. Due to the size and shape of the (Y) Oil Field concession, the new 3D seismic survey covered part of the (X) Oil Field (west and central areas).
This study aims to review this new dataset to provide further information on the potential structure of the (X) Oil Field and its relation to the (Y) Oil Field.

Geological description
This study focuses on the structure of (X) Oil Field at the Top Zubair reservoir level.
The stratigraphy of (X) and (Y) Oil Fields can be seen below in Figure ( Iraq and adjacent countries [3]. The formation comprises 380-400 m of alternating shale, siltstone and sandstone [4]. The type section was divided into five informal sand and shale units used for reservoir description [5]. To the SW the proportion of shale in the formation rapidly decreases. The thickness of the Zubair Formation ranges between 280 and 400 m with levels increasing towards northeast end of the field [6]. Porosity averages 25 percent and permeability, 1,000 millidarcies [7].

Aim of the study
The (X) Oil Field study aims is to review the new 3D seismic data set and provide additional new information on the (X) Oil Field, including the structure of the Top Zubair reservoir. The new interpretation could influence future depletion plans for both (X) and (Y) fields.
 Use New (Y) Oil Field 3D seismic data set which has some data covering (X) Oil Field.
 Identify the Top Zubair across (X) Oil Field.

Methodology
The study objectives were achieved through delivering the products outlined below:  Well-ties and seismic rock property analysis.  Review seismic attribute maps to QC the interpretation.
 Analyses of structure map and give an interpretation on structural closure of (X) Oil Field.   In some areas, the seismic was more difficult and required choosing between different potential interpretations. In these areas, sometimes the point to point picking function was used to ensure the preferred pick was chosen. Areas of more challenging interpretation have been highlighted in Figures (5) and (6).

Gridding and contouring, depth conversion and QC
The final QC'd horizon was then depth converted using the new velocity model which was provided by ROO. The depth horizon was then imported into its newly available Decision Space Software. This software provided quick and easy options for gridding and contouring [9]. Initially both the Time and Depth horizons were gridded with the same properties [10], [11], as a QC step and this is shown below in Figure (7).
The final parameters used for the gridding and contouring can be seen in Figure   (

Review of structural closure of (X) Oil Field
Using the final depth grid, a framework model is created to evaluate the structural closure of the Top Zubair horizon from (X) Oil Field to Rumaila. To evaluate closure, the original oil water contact (OOWC) for the fields was used (-3269m TVDSS) within the model. In Figure (10) cross sections have been reviewed to evaluate structural connectivity between the two fields. The results suggest that there is potential for structural connectivity between the two fields, in the middle and southern areas of (X) Oil Field, at Top Zubair level. However, there is uncertainty in this interpretation due to a lack of adequate well control in the saddle between (X) Oil Field and Rumaila, data quality, and a relatively smooth seismic velocity field.