Development drilling operations in the Zuluf Field / Khafji Reservoir (offshore Saudi Arabia) involve targets near the flanks of the main structure, where oil-filled sands are sandwiched between overlying gas and underlying water. Horizontal well technology is utilized to increase the reservoir footprint. This article relays recent geosteering examples in the Khafji Sand bodies. Demonstrated results show significant gains in well productivity through an advanced well placement procedure relying on real-time geosteering.

An asset team implemented a process of well placement in order to maximize the reservoir contact while drilling1 . The process involves continuous exchange of information between the well site and the office-based teams to allow fast and informed decisions. The success of the well placement process has been enhanced by preparation prior to drilling, continuous interpretation of the real time data while drilling and integrated teamwork throughout the project. A key technology in the well placement process is the use of realtime borehole density images in addition to the standard LWD data. Continuous interpretation of the image data (providing bed dip and thickness) and correlation of the LWD data, with the offset well data and geological models, provided the information necessary to maximize the reservoir contact "net pay" along the horizontal lateral section.

A series of wells have been drilled using the advanced well placement process. Examples illustrate how real time interpretation of the data by the team increased the net to gross ratio from 35% to 50%. The resultant increase in production demonstrates the value and the necessity of the process in the ongoing development of the field.

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