* Lotos plans to raise outstanding shares by up to 42.35 pct
* State-controlled group plans to fund upstream investments
* Oil field write-down to cut H1 net profit by 191 mln zlotys (Adds treasury comment, more details)
WARSAW, Aug 12 (Reuters) - Poland's second-largest oil refiner Grupa Lotos said on Tuesday it planned to issue shares worth about 1 billion zlotys ($320 million) to finance more oil and gas production.
The company also said a write-down on an oil field off Norway would knock 191 million zlotys off first-half net profit. Analysts had expected Lotos to post net profit of 34 million, without taking the one-off hit into account.
The company produced 146,000 tonnes of oil and 16 million cubic metres of gas from its Baltic fields last year but now wants to boost output of both over the coming three years.
Lotos is controlled by the state through a 53.2-percent stake. The group wants to issue up to 55 million shares - which would increase the total number of shares by 42.35 percent - and allow current shareholders to buy into the issue.
The Polish treasury, which oversees state assets, told Reuters it would say whether it will take part in any issue at a Sept. 8 meeting, when shareholders are due to vote on the plan.
Lotos wants to launch production of 250,000 tonnes of oil a year from its B8 Baltic field by the end of 2015.
It plans to start producing gas from the B4 and B6 fields by the end of 2017, with production from both seen at a combined 250 million cubic metres a year.
The group is also aiming to boost efficiency at its refining business and raise its share in the home retail market, where it competes with state-controlled PKN Orlen, to 10 percent next year from 9.2 percent now.
Lotos said it was taking a 545-million zloty full write-down on the Yme field off the Norwegian coast, due to a lack of new plans for the oil field. It said the charge would translate into a 191-million zloty reduction in first-half net profit.
The refiner controls 20 percent of Yme. Canada's Talisman Energy owns 60 percent, Germany's Wintershall , a unit of chemical giant BASF, has 10 percent, as does Norske AEDC, a unit of AOC Arabian Oil Company.
(1 US dollar = 3.1447 Polish zloty) (Reporting by Anna Koper and Adrian Krajewski; editing by David Clarke)