Oil-field service company Weatherford International PLC said Wednesday that it planned to continuing cutting jobs in the face of the sector’s lingering downturn and would slash about 15% of its already reduced workforce. Weatherford, one of the largest oil-field service companies in the world, said it would eliminate 6,000 position from a workforce of about 39,500. The cuts are slated to be made in the first half of 2016. In 2015,…