This paper presents a case study of developing a significant volume of super K compartmentalized oil reservoir with a large gas cap and bottom water aquifer in Abu Dhabi-UAE. The reservoir is a low relief heterogeneous carbonate, located in a complex environment represented by natural and artificial islands in the surface, shallow and medium water marine areas with subsurface lateral, and vertical heterogeneities as well as variation in reservoir fluid properties.The static and dynamic data were utilized to construct representative geological and dynamic models for the reservoir. The field development objective focused on maximizing the oil production and achieving 70% RF while minimizing the gas cusping, water conning and early breakthrough via super K interval.Nine years production dynamic data were available from 6 oil producers in addition to well testing Љ14 wellsЉ, core Љ11 wellsЉ, MDT Љ17 wellsЉ data during the appraisal phase. These data were used to quality control the initialization and history match phases. In preparation to the development options, the team included pressure support using water injection, lean gas injection, miscible gas injection, miscible WAG injection. The predicted reservoir performance of the super K oil reservoir indicated considerable gas production and high water production from the bottom water aquifer through super K interval in all the development options.It was a big challenge to reduce the amount of gas production, water production, and early breakthrough for all development options. A new development option was introduced to perform peripheral miscible Hydrocarbon WAG injection accompanied with optimization of the wells and completion intervals locations for producers and injectors, as wells as WAG cycle to minimize the gas production from the gas cap, water production from the aquifer, and early breakthrough. This resulted in significant enhancement to plateau length, sweep efficiency, and recovery factor. This paper provides the methodology followed to guide the development plan to fill in the uncertainty gap along with a detailed data acquisition and monitoring programs to better understand the reservoir behavior.
Structural architecture of fault zones, their distribution across the field and impact on migration pathways & reservoir permeability play an important part in field development. Inspiration for this study was limited understanding of role that faults play in brittle carbonate reservoirs. Extensive fault interpretation study was planned for quantification of orientations, segmentation, offset magnitudes and fault zones spacing to define their implications on fluid flow in terms of sealing capabilities within reservoirs. A systematic structural interpretation approach was established by exhausting the combination of regional tectonic history, 3D seismic interpretation techniques, advanced 3D visualization, BHIs, drilling data, production data, pressure data and MDT data. This resulted in better and more thorough definition of structures and hydrocarbon distribution in reservoirs. Structural history of the field was analyzed to tie fault related observations with known tectonic events affecting reservoirs. A simple structural restoration with available data indicated that structures & fault zones probably resulted from regional WNW-ESE compression during late Cretaceous period. 3D seismic interpretation techniques & 3D visualization were exploited to interpret faulted zones present in the field. Geometrical attributes were extracted from conditioned seismic data to enhance discontinuities & edges. Interpreted faults were later tied with wells crossing faulted zones using BHIs & drilling data. Thorough analysis reveals that major faults are actually assemblage of numerous segments. Furthermore, lateral and vertical displacement gradients are observed near tip lines of the fault planes. Relay-ramp behavior between fault segments are variable, mainly dependent on their orientation relative to prevailing maximum horizontal stress direction. Accordingly, positive (popups) and negative (sinkhole) structures can be found along the major faults. Two major faults having larger throws, as compared to other faults, divided the field into three parts, namely, northern, central & southern. Fault transmissibility varies as function of slip magnitude, diagenesis history leading to minerals filling, and their orientations relative to current maximum horizontal stress direction. Field dynamic data unveils that magnitude of slip is one of the most significant factors in explaining sealing capabilities of faults in reservoirs. Numerous wells have been drilled in central & southern parts of field with continuous production from wells in central part since 2005. Pressure records have shown no pressure change in southern part till date. Additionally, MDT results showed different FWLs and GOCs in both parts of field which also point to complete isolation. Northern part of field is yet to be appraised. Possibility of faults, with significant throw separating the northern from the central part of the field, acting as a seal may not be ruled out. An appraisal well with extensive acquisition program has been proposed to uncover hydrocarbon potential in northern part of field.
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