The Schiehallion field lies some 170 Km west of the Shetland Islands. The field, operated by BP, consists of a number of channelised sandstone reservoir sequences of Paleocene age. These reservoirs have significant compartmentalisation due to a number of faults and facies boundaries.
The field has been developed by a number of subsea high angle/horizontal production and water injector wells, the placement of which is critical to the drainage of the reservoirs. The wells are tied back to an FPSO from 3 drill centres. The combination of a subsea development and a hostile environment with strong winds and currents and wave heights up to 30m, leads to very high operating costs and time becoming a critical issue for any well operation. Thus data acquisition programmes have to be designed to both minimize rig time used as well as acquiring sufficient quality data to understand these complex turbidite fields.
Formation evaluation data has been routinely acquired whilst drilling for a number of years with no requirement for wireline backup. In-field appraisal targets have also been covered with FEWD only with no compromise on data quality or range.
This presentation uses a recent high angle injection well in the north of the Schiehallion field to demonstrate the use of FEWD to both fully understand the variations in reservoir quality along the wellbore and to optimally position the well in the four target sands. Reservoir quality was evaluated with an LWD magnetic resonance tool along with the more standard formation evaluation devices. Early E&A wells West of Shetland used wireline tools extensively to estimate permeability, irreducible water saturation and to detect thin bedded pay. The advent of the LWD tool now means that this type of analysis can carried out in the development arena as well which will prove of great value as the field development moves in to lower reservoir quality areas. The paper will show comparisons between the early wireline NMR data and that recently acquired whilst drilling showing the high quality achievable. The presentation will also show the use of FEWD density image data to estimate bed dip and its use to for gaining a clear understanding of the wellbore in relation to the seismic images of the sandbodies.
The paper hopes to demonstrate that even in a high cost subsea development scenario, data quality need not be compromised and can add significant value both to the current well delivery and to any future options.
Roy Greig is a Petrophysicist with INTEQ in Aberdeen. He has worked for Baker Hughes for nearly 18 years in both offshore and onshore technical roles with both wireline and LWD disciplines. For the last 3 years he has been working as a UK District Petrophysicist, including the role of UK LWD-NMR Service champion.