LONDON -- Oil prices have made steady gains this week: Brent crude for March delivery was up 1.8% to $113.70 per barrel on Friday afternoon, while WTI crude was up 0.7% to $96.30 shortly after U.S. markets opened on Friday. U.S. natural gas prices have slipped, and gas for February delivery was down 3.8% at $3.47/mmbtu shortly after U.S. markets opened on Friday.

Many investors prefer to invest in commodity ETFs rather than directly in futures, and holders of the United States Oil Fund (USO 0.09%) have seen their shares edge higher by 0.4% to $34.90 this week. The United States Natural Gas Fund (UNG 0.69%) has followed gas prices down and was 2.6% lower at $19.56 when U.S. markets opened on Friday.

The nature of oil and gas companies' businesses means that they can succeed or fail regardless of oil prices. This week's risers have all outperformed the price of oil by a big margin over the last month.

Range Resources (RRL) has climbed 14% to 3.8 pence so far this week, following two positive updates. In Trinidad, the company's drilling operations are progressing well, and it is also set to benefit from a revised farm-out agreement that will reduce the royalties it pays for each barrel produced, improving profit per barrel as production rises. Range also announced that it had taken a 19.9% stake in Latin American explorer Citation Resources, giving it exposure to two highly prospective oil and gas blocks in Guatemala.

BG Group (LSE: BG) has gained 14.5% to 1,162 pence over the last month, suggesting that investor sentiment may be improving again for the firm, which saw its share price drop by 20% late last year after it warned of flat production in 2013. BG recently announced that commercial production had begun on time and on budget at its Saphinoá field in offshore Brazil. BG's share price has also been lifted by repeated takeover rumours, with Royal Dutch ShellBP, and Exxon-Mobil mooted as possible buyers.

Russian oil producer Exillon Energy (EXI) has gained 18% to 155 pence since Jan. 15, reversing most of the decline caused when one of its largest shareholders, Worldview Capital Management, requested an EGM to remove Exillon's chairman and appoint three of its own nominees as board members. According to a statement released by Worldview, Exillon's management "have implemented a flawed operational strategy" that has resulted in disappointing oil production and share price performance.

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