Big Oil companies announced their second-quarter results last week. As expected, the results were stronger than the year-ago quarter largely because of higher oil prices. However, as investors, we must realize that external forces (like higher price realizations in the market) cannot be the only guiding factor when deciding which companies have really been growing organically and are capable of sustaining growth in the future. After all, that has the largest influence on the stock price over the long run -- not volatile commodity prices.

Operations matter
What really matters in the exploration and production space is whether these companies have been registering growth or, in other words, increasing production and expanding exploration activities. Here's the lowdown on the performances of some of the E&P majors:

ExxonMobil (NYSE: XOM): From the second quarter of 2010, production increased by 10% on an oil equivalent basis. Natural gas production shot up by 22%. The fundamentals look good. Capital expenditures and exploration costs went up by 58% to $10.3 billion, which is a very healthy sign indicating management's focus on expansion and growth. Returning to the Gulf of Mexico will further boost operations.

Downstream margins registered a phenomenal 95% increase, attributed to higher sales and foreign exchange rates.

Dividends per share increased by 7%, to $0.47. This giant is definitely a long-term investor's ideal pick.

Chevron (NYSE: CVX): Net production fell slightly, by a little over 2%. However, production did increase from individual projects in the United States and Canada. This should benefit the company in the long run, given the ever-increasing prospects of E&P in these countries. Capital expenditures increased to $13.4 billion for the first half of this year, from $9.4 billion for the corresponding period in 2010.

The company increased dividends by 8%, which is a positive move. However, from an operational standpoint, I should say that the second quarter was pretty mediocre when compared to Chevron's typical standards.

Royal Dutch Shell (NYSE: RDS-A) (NYSE: RDS-B): Production fell by 2%. Divestments had an impact on operations. The company has sold a few of its wells off the shores of Brazil for $400 million. Excluding divestments, production rose by 2% for the second quarter compared with last year.

Liquefied natural gas sales rose by an impressive 24%. Expect this segment to grow rapidly in the coming years. Otherwise, a major chunk of its 77% earnings growth is due to higher price realizations in the market.

Downstream operations weren't too impressive. Oil products sales fell by 8%, while chemical products sales volumes fell by 13%, when compared to the year-ago quarter.

ConocoPhillips (NYSE: COP): The worst performer among Big Oil companies, Conoco could not live up to its sterling reputation. Net income fell by almost 20% compared to the year-ago quarter. The company's divestment of LUKOIL holdings has hurt the bottom line. Total production declined 5.2%.

The refining and marketing segment was the only bright spot. Against a loss of $279 million during last year's second quarter, this segment posted an impressive $766 million profit this time around. Worldwide refinery utilization was 91% this quarter, which was another notable achievement.

The company is spinning off its R&M segment into a separate company. Investors should take note that the E&P arm could suffer as a result.

BP (NYSE: BP): Revenues rose by 37% while production saw a massive 11% drop. The lack of drilling in the Gulf of Mexico is still hurting the company. Also, the collapse of an Arctic exploration deal with Russian major OAO Rosneft is bound to affect expansion plans. The results thus far have been disappointing.

Chesapeake Energy (NYSE: CHK): Production increased by 9% year-over-year. Despite 84% of total production being natural gas, net profits rose by a fantastic 99% during the corresponding period. The company has battled successfully against the current bearish natural gas market. The simple lesson here is that the top companies know how to be successful in all types of markets. Increasing production is bound to bring down relative production costs and that's exactly what this company has been doing.

The second quarter saw the company adding 2.7 trillion cubic feet equivalent of reserves. The future looks really exciting for Chesapeake. Higher natural gas price realizations should only be a huge bonus. Investors should definitely take note.

Foolish bottom line
Big Oil companies have not been too impressive with regards to fundamental growth in the past quarter. Nevertheless, the overall picture going forward looks good.