--> --> Abstract: Recognition Criteria, Significance to Field Performance, and Reservoir Modeling of Sand Injections in the Balder Field, North Sea, by Nowell Briedis, Dag Bergslien, Andor Hjellbakk, Rob Hill, and Gordon Moir; #90082 (2008)

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Recognition Criteria, Significance to Field Performance, and Reservoir Modeling of Sand Injections in the Balder Field, North Sea

Nowell Briedis1, Dag Bergslien1, Andor Hjellbakk2, Rob Hill3, and Gordon Moir4
1Esso Norge AS, and ExxonMobil Subsidiary, Stavanger, Norway
24Sea Energy AS, Stavanger, Norway
3Mobil Producing Nigeria Unlimited, Lagos, Nigeria
4Tullow Oil, Cape Town, South Africa

The Balder Field comprises seven structurally and stratigraphically trapped oil accumulations, in three separate stratigraphic intervals of Paleocene to early Eocene age. The reservoirs are deep-water gravity flow deposited sands, draped and sealed by hemipelagic mud and volcanic tuff. Strong initial reservoir compartmentalization has been significantly modified by post-depositional sand remobilization and sand injection.

Sand injections were first recognized in 1969, in core from one of the early exploration wells. At the time, they were not thought to be significant. More than one hundred and fifty sand injections have subsequently been identified in cores from the exploration, appraisal and development drilling programs. This led to the realization that they were not just isolated occurrences, but a common phenomenon that could impact production. In addition to the cores, sand injections are now recognized and mapped using seismic and well log correlations, aided by principles derived from outcrop observation.

Initial geologic and reservoir modeling of the Balder Field consisted of separate models for each of the seven main accumulations. This was partially due to the complexity of sand distribution, and incomplete understanding of how individual sand bodies might be interconnected. It was also due to limitations in available software for building and simulating models of high complexity. The field went on production in September, 1999. In early 2000, when the first phase of infill drilling was being considered and more efficient tools for geologic and reservoir modeling were becoming available, the decision was taken to build a full-field model. To better understand how to incorporate the sand injections, outcrop analogs were studied to develop models for injection dimensions, orientations and distribution patterns.

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