Abstract

Due to their strong sub-surface heterogeneity many Middle Eastern fractured carbonate reservoirs are characterized by significant and wide range of uncertainties. This paper presents a case study of one of the largest and oldest oil fields in Oman. Despite over 35 years of production through various drive mechanisms, there remains an opportunity to realize significant additional value in the field.

This paper presents the biggest data acquisition program anywhere in Oman that is ongoing in a giant fractured carbonate field to support the planned water flood project there.

A total of 28 wells have been drilled on four inverted 5-spot patterns, each containing a central water injection well, four equidistant producers and two dedicated observation wells. Each well is deviated with an S-shaped hole, so that they arch away from the linear pad on surface and end up vertically in the reservoir building a square with the injector in the middle. All the patterns have been drilled, completed and been put on production. Initial surveillance activities have been already executed and analyzed.

The primary aim of the project is to gather data about the water flood behavior in different reservoir layers in the field by running reservoir analysis logs in the wells, measuring production data and injecting tracers to track the oil and water movements. The plan is to carry out up to 25 logs (EMI, PLT, PNN, Induction) and pressure surveys (BHP, PBU, PFO) per month, in addition to coring the central water injectors. The first pad "Phase1-1" started in September 2004, the second pad "Phase1-3" in March 2005, whereas the other two pads "Phase1-2 and Phase 2-3U" came on stream in August 2005.

Towards the end of 2006 the decision based on the pilot data results will be made on whether to extend the waterflood across the whole field. The alternative would be to rely on Gas/Oil Gravity Drainage, which is a lower investment option than water flood, but ultimately would achieve a lower recovery as well. Also combinations of both development options and/or an EOR development have to be evaluated.

This paper will highlight the water flood pilot set-up and the early results from this intensive data gathering and analysis for a water flood project.

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