The Q1 earnings picture for most oil companies has been a somber one, primarily due to the extended slump in commodity prices. Though some of the companies surpassed the Zacks Consensus Estimate, it was mainly because most estimates had been highly conservative ahead of the earnings season.The energy sector has been a drag on the overall market condition over the past few quarters and the situation is unlikely to change in Q1 either. Per the Earnings Trend report, the overall outlook is bearish as the sector is expected to register a massive 114.5% year-over-year decrease in earnings on a 31.8% plunge in revenues. Excluding the impact of the energy sector, the remainder of the S&P 500 index would witness negative earnings growth of 2.3%. Including the impact of the energy sector, the remainder of the index would witness negative earnings growth of 8%.Some heavyweights from the oil & gas drilling industry like Diamond Offshore Drilling, Inc. DO, Helmerich & Payne, Inc. HP and Halliburton Company HAL are set to report their Q1 results early next week. Let’s have a look how these industry bigwigs are likely to perform.Diamond Offshore Drilling Inc. is expected to report Q1 earnings on May 2. The company has an Earnings ESP of 7.41% and a Zacks Rank #3 (Hold). The combination of Diamond Offshore Drilling’s favorable Zacks Rank and a positive ESP makes us confident about an earnings beat.In the last quarter, the company’s earnings of 89 cents per share surpassed the Zacks Consensus Estimate of 53 cents and grew 23.6% from the year-ago earnings of 72 cents. (Read more: Will Diamond Offshore Drilling Beat on Earnings in Q1?)Helmerich & Payne Inc. is set to release fiscal Q2 results on May 2. The company has an Earnings ESP of 0.00% and a Zacks Rank #3 (Hold). The company’s Zacks Rank #3, which when combined with a 0.00% ESP, makes earnings prediction difficult.In the preceding three-month period, the Tulsa, OK-based firm delivered a massive positive surprise of 162.50%. The outperformance came on the back of lower rig expenses in its U.S. land segment. Coming to earnings surprise history, the company beat estimates in three of the last four quarters with a healthy average beat of 52.38%. (Read more: Can Helmerich & Payne Surprise Q2 Earnings?)Halliburton Company is slated to release Q1 results on May 3. The company was scheduled to report its earnings on Apr 25 but postponed the earnings call. The company has an Earnings ESP of 0.00% and Zacks Rank #5 (Strong Sell). We caution against Sell-rated stocks (Zacks Rank #4 or 5) going into the earnings announcement, especially when the company is seeing negative estimate revisions. It is to be noted that the company expects lower sequential revenues from its North American operations due to the ongoing oil price weakness.Last quarter, the company posted a positive earnings surprise of 29.17%. In fact, Halliburton has a positive four-quarter average earnings surprise of 28.80%. (Read more: Will Halliburton Surprise at Delayed Q1 Earnings Call?)Don’t miss out on our full earnings release articles for these two oil refining stocks, as the actual results might hold some surprises!Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report HALLIBURTON CO (HAL): Free Stock Analysis Report HELMERICH&PAYNE (HP): Free Stock Analysis Report DIAMOND OFFSHOR (DO): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research