Shares in Russia-focused oil and gas explorer PetroNeft Resources took a tumble on Tuesday as the update on operations at Licences 61 and 67 in the Tomsk Oblast region revealed mixed results.The Kondrashevskoye No. 2 delineation well in Licence 61 has been drilled and confirmed 2.3m of net pay in the J1 interval, consistent with the No. 1 well which discovered the oil field in 2008. Neither well has encountered the oil water contact for the field, which broker Ambrian says "bodes well from an in-place reserve perspective."Development drilling results, however, were mixed, with Pad 2 net pay thickness showing better reservoir development, while Pad 3 showed oil-saturated pay zones "thinner than previously anticipated", PetroNeft said. Therefore, more wells have been planned for Pad 2, and less for Pad 3."On the production front, we understand that a number of wells have so far performed sub-optimally; consequently, production is currently running slightly below where management would ideally like it to be," said Ambrian."The development programme is well underway and we have learned a lot from the drilling to date. The Lineynoye oil field extends further north and has thicker oil pays than previously thought whereas the Pad 3 area has some thinner pays," said chief executive Dennis Francis. "We will continue to dynamically adjust the drilling and completion programme to ensure the optimum long term reserve and production outcome for Lineynoye and the surrounding discoveries."---BC