This is the first attempt to produce oil from fractured basement reservoirs in UK waters.
Two wells have been connected to the FPSO Aoka Mizu, with the company attempting to sustain combined production rates up to 20,000 b/d.
But this has not been possible of late due to the instability in the flow regime on the 205/21a-7Z well as a result of interference between the wells.
Hence the decision to shut-in 205/21a-7Z well for the time being and return to a period of testing of maximum sustainable rates solely from the 205/21a-6 well.
At the time of the instability, water production from 205/21a-7Z was in line with levels seen over the previous weeks.
Currently Lancaster is producing around 10,300 b/d from 205/21a-6 well, a rate which Hurricane plans to increase in stages in order to determine its maximum sustainable level.
Chief executive Dr Robert Trice said the degree of interference encountered was unexpected, adding that while both wells delivered high productivity individually, their proximity and associated interference behavior requires further data acquisition before the company can be confident about optimum long-term well rates.