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In the South of Oman, several billion barrel heavy oil fields are located in a clastic reservoir setting. Many of the fields typically contain 200 - 2000 cP viscosity oil in good quality reservoirs at depths of about 1000 meters from the surface. These fields have usually been densely developed, often with horizontal wells, and produced cold for many years. Nevertheless, most of the oil-in-place will not be produced conventionally unless a suitable EOR technique is applied. Steam and polymer flooding are two potential EOR techniques, but each option faces technical and economic challenges. This paper focuses, for one of the fields in the Haima group, on the common challenge of well count reduction and utilizing the existing horizontal well stock by a combination of creative thinking and novel technology. New vertical well patterns lead to high well counts and vertical injectors generally exhibit poor conformance in relation to existing horizontals. Even when the existing wells are closed in, the horizontal sections, in particular from dual-laterals, can often not be abandoned and will keep acting as conduits in a vertical pattern layout. New horizontal wells with conformance control equipment can provide a cost effective solution that compliments the existing horizontal well stock and provides better conformance and injectivity than vertical wells. Conformance control equipment that can withstand steam temperatures has recently been developed. For both the steam and polymer flooding options, the production technology and reservoir engineering aspects of horizontal well conformance control will be discussed in detail and compared to vertical wells. Simulation modelling results will demonstrate that even in relatively homogeneous reservoirs, conformance issues can significantly reduce recovery if not properly mitigated. In particular, injector versus producer conformance control, the number of discrete completion intervals and novel technology solutions will be discussed.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAn intensely fractured reservoir in central Oman is being developed by injecting steam into the crest of the field, heating the oil in the matrix and producing it via a Gas-Oil Gravity Drainage (GOGD) process. Both the static and the dynamic data support a strongly fractured (and leached) reservoir. Building 3D full field fracture models that capture the possible scenarios proved to be a challenge, largely because to date (i) most wells in the crest are vertical, (ii) a limited number of horizontal wells have been drilled on the flanks, (iii) seismic quality is relatively poor, and (iv) dynamic constraints on the permeability structure are limited, especially on the flanks. A new 3D fracture software tool (SVS) has been used to maximize the value of fracture-related reservoir data through improved integration, visualization, analysis and correlation. Rapid interactive analysis of the data set allows the user to efficiently characterize and understand the nature of the fracture system and its relationships to other reservoir parameters. The data analysis indicates that two end member fracture system scenarios could be present in the reservoir i) a mechanical stratigraphy related and ii) fault/corridor related fracture system. This is particularly true of the flank wells, which despite being mostly located away from the main seismic scale faults on the crest, have evidence for fault related fracture clusters at intervals down the well bore. For these end member, and intermediate scenarios, "Low", "Medium" and "High" Case models were created using fracture trend maps/grids that combine the data and a range of geological constraints. More remote information was included from outcrop fault patterns in northern Oman. A combination of detailed process based discrete fracture generation and rapid fracture attribute generation was used to populate over 15 full field simulation grids capturing the range of remaining uncertainty of the fracture system across the field.

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