Development Of Flank Areas In A Giant Carbonate Field With Optimal Well Placement Of Horizontal Wells
- Sameer A. Khan (Zakum Development Co.) | Ali Nadeem Al-Shabeeb (Zakum Development Co.) | Zankar Jani (ZADCO) | Youcef Azoug (ZADCO Petroleum Co) | Nguyen Minh (ZADCO) | Harshad Patel (ZADCO)
- Document ID
- Society of Petroleum Engineers
- Abu Dhabi International Petroleum Conference and Exhibition, 11-14 November , Abu Dhabi, UAE
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.5.5 Evaluation of uncertainties, 5.2 Reservoir Fluid Dynamics, 5.5.8 History Matching, 5.4.1 Waterflooding, 5.6.4 Drillstem/Well Testing, 5.2.1 Phase Behavior and PVT Measurements, 5.8.7 Carbonate Reservoir, 5.4.2 Gas Injection Methods, 1.6 Drilling Operations, 4.3.4 Scale, 5.7.2 Recovery Factors, 5.1 Reservoir Characterisation, 5.1.2 Faults and Fracture Characterisation, 5.5 Reservoir Simulation
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Flank areas pose a particular field development challenge in giant fields with low dip where the transition zone is spread over a large area. Successful development of flank areas depends on accurate reservoir characterization, in particular, water saturation distribution in addition to the optimal placement of wells, both areally and vertically. In relatively thin reservoirs, horizontal wells are generally preferred to increase reservoir contact using lower well counts. Proper spacing and vertical placement of horizontal wells are, however, critical. Well spacing is closely linked to oil recovery, pressure support, and sweep efficiency. Similarly, placement of horizontal wells in the right layer is vital for maximum vertical sweep. In order to test initial concept in the field, two existing producers were converted into injectors and pressures were monitored at the offset producers. Surveillance showed that the injectors were able to support producers 1 km away. This paper describes the process of arriving at the optimal well placement for maximizing oil recovery in the flank areas. This study is applicable to giant oil fields with large flank areas which pose significant development challenges.
The subject oil field is one of the world's largest offshore carbonate reservoirs and has a production life in excess of 100 years. Field structure, cross-section, and basic field information has been provided earlier by Modavi et al. (2010). The field was historically developed with well head tower platforms (WHPTs) made of steel structures and a combination of vertical and 1 km long horizontal wells in a five-spot pattern. Modavi et al. (2008), later proposed a new development plan which deployed artificial islands as drilling centers and utilized extended reach drilling (ERD) technology to drill much farther. In addition, well counts were significantly reduced by deploying longer (3 km) horizontal laterals referred to as maximum reservoir contact (MRC) wells (Marzouqi et al., 2010). The development plan was comprised of both surface and subsurface components which were effectively integrated to provide maximum flexibility in terms of development options as well as handling of reservoir uncertainties. Since the aquifer support for the subject field is weak, the development consists of a waterflood with line drive to be later followed by gas injection. This island-based plan was approved by shareholders in 2008 and implementation began shortly thereafter.
The island-based development plan includes a comprehensive subsurface development plan based on the available data and prediction tools at the time. Development plan optimization soon began as more data were being acquired and new reservoir models were built. This work is focused on development plan optimization of two large flank areas of the biggest reservoir in the subject field (South and East Flanks in Fig. 1). These flank areas contain very large capillary transition zones which although is only a few hundred feet high, yet extends to several kilometers areally due to very low reservoir dip (1 to 2 degrees) in a 150 ft thick reservoir. Therefore, appropriate areal and layer placement of MRC wells in flank areas is a critical task that requires careful attention. This is discussed next.
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