Partners Tullow and partners Anadarko and Kosmos will need to invest about $400m (€312m) to fix mechanical issues related to well designs at the company's Jubilee oil field off the coast of Ghana, Tullow added. The partners have already invested $3.4bn to develop the field. "The key drag on production appears to be the Jubilee field, where well-decline rates have been much higher than expected due to a well-completion design issue," Numis Securities analyst Sanjeev Bahl said yesterday. Tullow has no concrete news of a simmering dispute between the company and the government in Uganda, which has prevented it from finalising a deal to sell a one-third stake in its Ugandan oil discoveries to French oil company Total and China's Cnooc for $2.9bn. Tullow and the Ugandan government are "all working hard to get things finalised before the end of January," chief financial officer Ian Springett told analysts. Previous dates for a proposed resolution have come and gone.