Lancaster test proves better than expected
OE Staff
Monday, September 15, 2014
Fractured basement reservoir explorer Hurricane Energy says post-well data analysis of its 1km horizontal appraisal well 205/21a-6 well test in Q2 this year has shown better than expected results.
The firm said the well, which tested the west of Shetland Lancaster oil discovery West of Shetland, was optimally located to benefit from a highly connected fault/fracture network and an underlying 300m oil column (Hurricane's - 2C estimate of field oil down to, or ODT).
"The results from third party analysis combine to demonstrate a very good quality reservoir which could deliver single well rates of 20,000 STB/d - significantly ahead of initial expectations of well productivity," said Hurricane.
Summary information:
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As previously announced, the well test achieved a sustainable natural flow rate of 5300 STB/d and a flow rate using artificial lift (using an electrical submersible pump) of 9800 STB/d. Both rates were constrained by surface equipment.
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Well flowed for a total of 78 hours and shut in for a maximum of 22 hours.
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Shut in pressures indicate a rapid pressure response and no observable pressure decline.
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Data from this well indicates that under production conditions and a moderate 120 psi drawdown the basement reservoir could deliver 20,000 STB/d from a single well.
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PVT and geochemical analysis reconfirm the wellsite analysis that the oil is 38 degrees API and consistent with that produced from previous Lancaster wells.
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Well productivity index of 160/STB/d/psi demonstrates a very good quality reservoir pressure capable of delivering sustained commercial flow under production conditions.
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Tidal data and modelled well test pressure response indicate that the intervening fractured basement rock, as well as the seismic scale fault zones, contributed to flow. The tidal data is extremely important as it not only corroborates the pre-drill geological model but provides new analysis that demonstrates a highly permeable, well connected fracture network.
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Pressure response indicates that the drilling programme was successful at minimising skin damage to the near wellbore environment.
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No evidence of barriers within the fractured basement reservoir in the duration of this test.
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Target faults identified from pre-drill seismic analysis were encountered as expected, providing the company with a high degree of confidence for future well placement.
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Additional upside was encountered from an interval of previously undrilled Jurassic-Cretaceous sandstone. The sandstone is oil bearing, and has an average porosity of 16%; however further subsurface work is required to quantify the materiality of this reservoir sandstone.
Read more: Fractured basement reservoirs, a new play for the North Sea.
Exploring the under-explored on the UKCS, including the fractured basement