S&P Global Market Intelligence presents a periodic rundown of selected ratings actions on energy companies. The changes, confined to upgrades, downgrades and changes in outlook, are listed by announcement date in reverse chronological order.

May 29

* Fitch Ratings lifted its ratings on Kinder Morgan Inc. by one notch, citing the cash flow stability of the company's asset base and improved leverage, among other factors. The ratings outlook was revised to stable from positive.

May 27

* S&P Global Ratings changed its outlook on Italian oil and gas engineering company Saipem SpA from negative to stable while affirming its BB+ rating on Saipem and its debt instruments.

May 26

* Fitch Ratings revised its outlook on Ecopetrol SA, Oleoducto Central SA, or OCENSA, and AI Candelaria (Spain) S.L.U. to negative from stable.

May 24

* S&P Global Ratings has downgraded its ratings on Texas-based Schlumberger Ltd., based on its expectation that oilfield services companies will not be able to generate high operating margins.

May 22

* Fitch Ratings assigned Siemens Gamesa Renewable Energy SA a BBB long-term issuer default rating, with a stable outlook.

May 20

* S&P Global Ratings revised its outlook on Duke Energy Corp. and its subsidiaries to negative from stable on expectations of weaker financial measures.

May 17

* The Florida Public Service Commission's recent decision to continue allowing Florida Power & Light Co. to use tax savings to cover $1.3 billion in costs related to Hurricane Irma is a credit positive for the NextEra Energy Inc. subsidiary, according to Moody's.

* Moody's lowered its ratings on Northwest Natural Gas Co. by one notch, saying the utility's financial performance in the next few years is expected to be in line with companies of the same rating level. The outlook was revised to stable from negative.