US banking giants, Citigroup and Wells Fargo have witnessed a sharp decline in profit during 2015 apparently due to the oil riot. Both the Wall Street banks have lifted their reserves for provisioning against default investments from energy companies. Such provisioning reflects the woes of clients involved in the petroleum business.

However, San Francisco based Wells Fargo has surpassed Citigroup, the former No. 1, in terms of assets. The horse drawn stage coach logo bearing bank has appeared as the third largest bank in the US at the end of 2015. It has posted a net asset figure of $1.79 trillion leaving behind the umbrella logo holding Citigroup whose asset value stands at $1.73 trillion, reports USA Today.

The threat approaches with greater vicinity and oil prices have finished below $30 a barrel of US benchmark crude for the first time since 2003 on Friday. Meanwhile, the London Brent crude has dipped even further, ended below $29.

Both the prices are down by more than half from a year ago and more than 21 percent since the end of 2015. The falling price is hitting a broad swathe of companies including oil, gas and coal producers, refiners, pipelines, and service companies, reports Yahoo News.

Citigroup has reported fourth quarter earnings in 2015 for $3.3bn (£2.3bn), nearly ten times during the same period of the previous year. But it has been forced to make provisions for $250m (£175m) for its energy portfolio.

Combined reserves for the previous three quarters of 2015 appear to be equal to the fourth quarter's provisioned amount. Instead of increasing the asset value eventually, the amount has been blocked by the seriously hit energy sector, according to a report published in Sky News.

Citigroup's stock price has been reduced by 6% to $42.47 a share on Friday. Meanwhile, Wells Fargo stock has dropped by 3.6% to $48.82 amid concerns over falling oil price.

However, the stage coach bearer hasn't suffered much from rising loan costs during the fourth quarter like JP Morgan Chase Bank. This is because the former's real estate portfolio has helped to somehow offset the oil market crunch and related aftermaths.

The Wall Street Banks have been reported to suffer immensely due to the continuous fall in the oil market. Investments in the energy sector have compelled the banks to refrain from capital gains. However, strong contribution from the real estate portfolio has helped Wells Fargo to overcome the energy sector plunge. This has appeared as the differentiating factor that led the Wall Street giant to appear as the third largest bank in the US in terms of asset value, leaving behind former No. 1, Citigroup.