UPDATE 3-Exxon replaces 133 percent of reserves in 2009

* Proved reserve additions total 2 billion BOE

* Exxon shares up 1.4 percent

* Reserves 51 pct liquids, 49 pct gas (Adds analyst comment; updates share price)

By Anna Driver

HOUSTON, Feb 16 (Reuters) - Exxon Mobil Corp (XOM.N) added 2 billion barrels of oil equivalent to its proved oil and gas reserves in 2009, or 133 percent of its production for that year, the largest U.S. oil company said on Tuesday.

Large Western oil companies' efforts to boost reserves have been stalled as they are increasingly barred from investing in the world's richest oil prospects.

For example, Venezuela and Russia reserve their richest fields for state-owned oil companies.

Reserve additions from the Papua New Guinea LNG project and the Gorgon Jansz liquefied natural gas project in Australia totaled almost 1 billion BOE, Exxon said.

To estimate its reserves, Exxon used long-term pricing instead of the 12-month averages required under rules from the U.S. Securities and Exchange Commission.

Using the SEC's pricing basis, proved reserves replacement was 1.5 billion BOE, replacing 100 percent of production, including the effect of asset sales, oil sands extracted by mining and equity company reserves.

On that basis, Raymond James analyst Pavel Molchanov described the company's 2009 reserve replacement rate as "uninspiring," but noted it was an improvement over the last two years, where Exxon reported reserve declines.

Investors see replacement of more than 100 percent of annual oil and gas output is seen as a sign of growth.

Exxon Mobil's proved reserve base, using the company's definition of year-end reserves, increased to 23.3 billion BOE in 2009. Those reserves are split nearly evenly between liquids and gas.

Shares of Exxon rose 1.4 percent to $65.71 in afternoon New York Stock Exchange trading, while the Chicago Board Options Exchange index of oil companies .OIX gained 2.5 percent. (Reporting by Anna Driver, editing by Gerald E. McCormick, Derek Caney and Lisa Von Ahn)