The Machar Oil Field, UK Central North Sea: impact of seismic reprocessing on the development of a complex fractured chalk field

Abstract

Abstract The Machar Field in the UK Central North Sea is a fractured Cretaceous chalk and Palaeocene sandstone oil reservoir, developed around a tall salt diapir. Machar was discovered in 1976 and, after a lengthy appraisal including extended flow tests starting in 1994, has been developed in a phased manner from 1998 through a multi-well subsea development. The steeper eastern flank has historically lacked coherent reflectivity on seismic data and has remained undrilled. The geological possibility of a reservoir on the east flank provided motivation for extensive seismic reprocessing between 2005 and 2007, and the seismic interpretation showed both a chalk and a sand presence in this area of the field. Simulation modelling suggested that a well here would deliver substantial incremental field volumes. Confidence in the new seismic interpretation reduced the subsurface risk associated with the area, and a new subsea drill-centre reduced the drilling risks and costs sufficiently to allow a Machar East well to be sanctioned. Successful well results in 2008 changed the entire perception of the field and acted as a springboard for further development including a sidetrack in the northern area and a third injection well to support the east, which was drilled and completed in the summer of 2010.