The Enfield oil field, on Australia's Greater North-West Shelf, has now produced over 50 million barrels of oil. The field is a water flood development with both downdip and updip water injection wells. Faults and baffles within the reservoir create a complex dynamic system that can only be understood with the integration of 4D seismic data. Monitor surveys in 2007 and 2008 have made major contributions to reservoir management and identification of infill drilling opportunities.This paper highlights the value of fully integrating 4D seismic into reservoir management, and the rationale for sidetracking a water injector well at short notice to provide pressure support to the field's largest producing oil well. Oil production from this well was dropping rapidly and the need to improve pressure support was clearly evident. It only became clear how best to achieve this upon delivery of new 4D results.The reservoir model directed attention towards insufficient water injection downdip and the opportunity to sidetrack these injection wells closer to the production wells was under consideration. However, results of the December 2008 4D monitor survey became available at this time, and indicated a reservoir baffle between the oil producer and the downdip injectors, which diverts water away from the producer. Thus improving injectivity at these downdip water injector wells would have had little impact on the failing producer.The 4D seismic data also indicated that water from a key updip injector was being deflected away from the producer. The difference here was that the baffle was close to the water injector and not the oil producer. The opportunity to sidetrack this water injector across the baffle was rapidly progressed, with the injector sidetrack drilled and completed in mid 2009. Pressure support at the oil producer was seen within days of commencing injection in the sidetracked well. Revenue from increased oil production paid back the cost of the injector sidetrack and the 4D monitor survey within two months of startup. The involvement of all subsurface disciplines was a key success factor in the outcome.
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.
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