By Tess Stynes 

Kinder Morgan Inc. said it is offering $6 billion of senior notes to help fund the energy company's $44 billion deal to consolidate four related pipeline companies.

The bond offer comes a day before the consolidation transaction is expected to close.

According to a filing with the U.S. Securities and Exchange Commission, Kinder Morgan is offering five series of debt that come due from 2017 to 2045. The notes carry interest rates ranging from 2% to 5.55%.

Kinder Morgan initially unveiled its debt offer plans Monday but didn't provide financial terms. Dow Jones Newswires had reported the size was expected to be about $5 billion.

Companies have been diving into the U.S. bond market this year as interest rates remain relatively low.

Last week, Chinese Internet company Alibaba Group Holding Ltd. launched a debut $8 billion bond sale, one of the largest corporate-bond sales of the year. And in November, Walgreen Co. raised $8 billion through a debt sale to help pay for its purchase of international pharmacy chain Alliance Boots GmbH.

Kinder Morgan unveiled its consolidation plan on Aug. 10. Kinder Morgan Inc., which manages the pipeline businesses and is the general partner of the other three entities, would acquire Kinder Morgan Energy Partners, El Paso Pipeline Partners and Kinder Morgan Management LLC, which is for institutions and is eligible for a tax-free exchange of shares.

Mike Cherney contributed to this article.

Write to Tess Stynes at tess.stynes@wsj.com

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