NEW YORK (TheStreet) -- With MPLX LP (MPLX - Get Reportagreeing to buy MarkWest Energy Partners LP (MWE) for nearly $16 billion, and an Iran nuclear deal set to further affect world energy markets, we decided to see if there are any stocks in the oil and gas storage and transportation sub-sector worth investing in.

The sector's revenue is based on dollars per volume stored or transported. In the current environment of ample supplies, and rising demand for energy due to a growing economy, firms and industries that use energy increase their stockpiles or inventories. This is beneficial to the energy storage and transportation sector. Since oil prices crashed last year, the sector benefited greatly; an oil glut means it's a seller's market for storage. 

So, what are the best oil and gas storage and transportation investors should be buying? Here are the top four, according to TheStreet Ratings,TheStreet's proprietary ratings tool.

TheStreet Ratings projects a stock's total return potential over a 12-month period including both price appreciation and dividends. Based on 32 major data points, TheStreet Ratings uses a quantitative approach to rating over 4,300 stocks to predict return potential for the next year. The model is both objective, using elements such as volatility of past operating revenues, financial strength, and company cash flows, and subjective, including expected equities market returns, future interest rates, implied industry outlook and forecasted company earnings.

Buying an S&P 500 stock that TheStreet Ratings rated a buy yielded a 16.56% return in 2014 beating the S&P 500 Total Return Index by 304 basis points. Buying a Russell 2000 stock that TheStreet Ratings rated a buy yielded a 9.5% return in 2014, beating the Russell 2000 index, including dividends reinvested, by 460 basis points last year.

Check out which oil and gas storage and transportation made the list. And when you're done, be sure to read about which semiconductor stocks to buy now. Year-to-date returns are based on July 13, 2015, closing prices. The highest-rated stock appears last.

EQM ChartEQM data by YCharts
4. EQT Midstream Partners, LP (EQM - Get Report)

Rating: Buy, A-
Market Cap: $5.8 billion
Year-to-date return: -7.1%

EQT Midstream Partners, LP provides natural gas transmission, storage, and gathering services in southwestern Pennsylvania and northern West Virginia. It owns, operates, acquires, and develops midstream assets in the Appalachian Basin.

"We rate EQT MIDSTREAM PARTNERS LP (EQM) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its robust revenue growth, impressive record of earnings per share growth, compelling growth in net income, expanding profit margins and good cash flow from operations. We feel its strengths outweigh the fact that the company has had lackluster performance in the stock itself."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • The revenue growth greatly exceeded the industry average of 38.9%. Since the same quarter one year prior, revenues rose by 43.5%. Growth in the company's revenue appears to have helped boost the earnings per share.
  • EQT MIDSTREAM PARTNERS LP reported significant earnings per share improvement in the most recent quarter compared to the same quarter a year ago. The company has demonstrated a pattern of positive earnings per share growth over the past two years. We feel that this trend should continue. During the past fiscal year, EQT MIDSTREAM PARTNERS LP increased its bottom line by earning $3.47 versus $2.49 in the prior year. This year, the market expects an improvement in earnings ($4.54 versus $3.47).
  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Oil, Gas & Consumable Fuels industry. The net income increased by 73.3% when compared to the same quarter one year prior, rising from $54.99 million to $95.31 million.
  • The gross profit margin for EQT MIDSTREAM PARTNERS LP is currently very high, coming in at 80.54%. It has increased from the same quarter the previous year. Along with this, the net profit margin of 61.56% significantly outperformed against the industry average.
  • Net operating cash flow has significantly increased by 123.95% to $114.66 million when compared to the same quarter last year. In addition, EQT MIDSTREAM PARTNERS LP has also vastly surpassed the industry average cash flow growth rate of -53.30%.

BPL ChartBPL data by YCharts
3. Buckeye Partners, L.P. (BPL - Get Report)

Rating: Buy, A-
Market Cap: $9.4 billion
Year-to-date return: -2%

Buckeye Partners, L.P. owns and operates liquid petroleum products pipeline systems in the United States. The company operates through four segments: Pipelines & Terminals, Global Marine Terminals, Merchant Services, and Development & Logistics.

"We rate BUCKEYE PARTNERS LP (BPL) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its compelling growth in net income, reasonable valuation levels, good cash flow from operations, largely solid financial position with reasonable debt levels by most measures and growth in earnings per share. We feel its strengths outweigh the fact that the company has had lackluster performance in the stock itself."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Oil, Gas & Consumable Fuels industry. The net income increased by 23.4% when compared to the same quarter one year prior, going from $90.47 million to $111.61 million.
  • Net operating cash flow has significantly increased by 599.01% to $237.62 million when compared to the same quarter last year. In addition, BUCKEYE PARTNERS LP has also vastly surpassed the industry average cash flow growth rate of -53.30%.
  • The debt-to-equity ratio is somewhat low, currently at 0.98, and is less than that of the industry average, implying that there has been a relatively successful effort in the management of debt levels. Despite the fact that BPL's debt-to-equity ratio is low, the quick ratio, which is currently 0.57, displays a potential problem in covering short-term cash needs.
  • BUCKEYE PARTNERS LP's earnings per share improvement from the most recent quarter was slightly positive. This company has reported somewhat volatile earnings recently. But, we feel it is poised for EPS growth in the coming year. During the past fiscal year, BUCKEYE PARTNERS LP reported lower earnings of $2.79 versus $3.23 in the prior year. This year, the market expects an improvement in earnings ($3.70 versus $2.79).

SEP ChartSEP data by YCharts
2. Spectra Energy Partners, LP (SEP)

Rating: Buy, A-
Market Cap: $13.9 billion
Year-to-date return: -17.6%

Spectra Energy Partners, LP operates as an investment arm of Spectra Energy Corp.

"We rate SPECTRA ENERGY PARTNERS LP (SEP) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its revenue growth, increase in net income, expanding profit margins, growth in earnings per share and largely solid financial position with reasonable debt levels by most measures. We feel its strengths outweigh the fact that the company has had somewhat disappointing return on equity."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • The revenue growth greatly exceeded the industry average of 38.9%. Since the same quarter one year prior, revenues slightly increased by 4.3%. This growth in revenue appears to have trickled down to the company's bottom line, improving the earnings per share.
  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Oil, Gas & Consumable Fuels industry. The net income increased by 21.1% when compared to the same quarter one year prior, going from $242.00 million to $293.00 million.
  • The gross profit margin for SPECTRA ENERGY PARTNERS LP is rather high; currently it is at 64.85%. Regardless of SEP's high profit margin, it has managed to decrease from the same period last year. Despite the mixed results of the gross profit margin, SEP's net profit margin of 48.34% significantly outperformed against the industry.
  • The current debt-to-equity ratio, 0.58, is low and is below the industry average, implying that there has been successful management of debt levels. Although the company had a strong debt-to-equity ratio, its quick ratio of 0.93 is somewhat weak and could be cause for future problems.
  • SPECTRA ENERGY PARTNERS LP has improved earnings per share by 14.3% in the most recent quarter compared to the same quarter a year ago. This company has reported somewhat volatile earnings recently. But, we feel it is poised for EPS growth in the coming year. During the past fiscal year, SPECTRA ENERGY PARTNERS LP reported lower earnings of $2.84 versus $7.16 in the prior year. This year, the market expects an improvement in earnings ($2.93 versus $2.84).

MMP ChartMMP data by YCharts
1. Magellan Midstream Partners, L.P. (MMP - Get Report)

Rating: Buy, A-
Market Cap: $16.8 billion
Year-to-date return: -10.4%

Magellan Midstream Partners, L.P. engages in the transportation, storage, and distribution of refined petroleum products and crude oil in the United States. It operates in three segments: Refined Products, Crude Oil, and Marine Storage.

"We rate MAGELLAN MIDSTREAM PRTNRS LP (MMP) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its notable return on equity and expanding profit margins. We feel its strengths outweigh the fact that the company has had generally high debt management risk by most measures that we evaluated."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • The return on equity has improved slightly when compared to the same quarter one year prior. This can be construed as a modest strength in the organization. When compared to other companies in the Oil, Gas & Consumable Fuels industry and the overall market, MAGELLAN MIDSTREAM PRTNRS LP's return on equity exceeds that of the industry average and significantly exceeds that of the S&P 500.
  • The gross profit margin for MAGELLAN MIDSTREAM PRTNRS LP is rather high; currently it is at 55.05%. Regardless of MMP's high profit margin, it has managed to decrease from the same period last year. Despite the mixed results of the gross profit margin, MMP's net profit margin of 35.17% significantly outperformed against the industry.
  • Despite the weak revenue results, MMP has outperformed against the industry average of 38.9%. Since the same quarter one year prior, revenues fell by 15.6%. Weakness in the company's revenue seems to have hurt the bottom line, decreasing earnings per share.
  • MAGELLAN MIDSTREAM PRTNRS LP's earnings per share declined by 24.3% in the most recent quarter compared to the same quarter a year ago. This company has reported somewhat volatile earnings recently. We feel it is likely to report a decline in earnings in the coming year. During the past fiscal year, MAGELLAN MIDSTREAM PRTNRS LP increased its bottom line by earning $3.68 versus $2.56 in the prior year. For the next year, the market is expecting a contraction of 11.0% in earnings ($3.28 versus $3.68).
  • The change in net income from the same quarter one year ago has exceeded that of the Oil, Gas & Consumable Fuels industry average, but is less than that of the S&P 500. The net income has decreased by 24.3% when compared to the same quarter one year ago, dropping from $242.55 million to $183.64 million.