Abstract
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.
