Innovative Multi-Zone Water Injection: The Enfield ENC05 Story

Abstract The Enfield oil development, on Australia's Greater North-West Shelf, has now produced over 50 MMBBL oil. Enfield has been developed with both downdip and updip injection wells for pressure support and recovery. An injector / producer pair were drilled in 2009 to develop the Enfield Sliver South area. For the project to be economically viable the wells needed to drain two fault compartments. In particular, water injection into each compartment needed to be proportional to the expected reserves. Recovery was expected at approximately 1.7 MMBBL from Segment 3 and 3.3 MMBBL from Segment 4. Due to the location of subsea infrastructure a single water injection well needed to be drilled from the west with the first sands intersected in Segment 3, the smallest block, and then Segment 4 which required the most injection. One solution was to drill a dual lateral injection well. However, the cost and difficulty with injection control of this option was prohibitive for the project. A horizontal well design using two sets of stand alone screens, with Inflow Control Devices (ICD's), was selected to access both fault blocks. This provided both the flow control and the sand control required for these reservoirs. This paper highlights the innovative ICD solution adopted to achieve the required proportional water injection and avoid over injection into Segment 3 (at the heel). Various models were constructed to analyse injection scenarios with variables including; sand penetration and quality, compartment volumes, near wellbore skins, producer off take rates, and pressures. Upon drilling the well, and obtaining reservoir data, the final completion configuration was selected. This included the placement of three screens with 6 ICD ports open per screen for Segment 3 (at the heel of the well) and three screens with 32 ports open per screen in Segment 4 (at the toe of the well). Both Matrix and Fracture injection have been observed in ENC05. The well is routinely exceeding 30,000 BWPD, at fracture rates through the ICD's, into both compartments and successfully supporting the over 20,000 BOPD oil producer to the north. This was the first time high rate proportional control, including fracturing, has ever been done with ICD's to our knowledge.