The private-equity firm Energy Capital Partners provided more than $1 billion in additional equity to midstream asset company USD Group LLC and its affiliates, the company said Sept. 22. The partnership closed, the company added.

Energy Capital purchased an equity interest in USD Group’s parent entity, US Development Group LLC, the company said. Proceeds will support the shareholder base, growth projects and the balance sheet, USD Group added.

Houston-based USD Group LLC and its affiliates provide and operate rail logistics and other midstream infrastructure across North America.

Energy Capital Partners, based in Short Hills, N.J. invests in North American energy, including midstream oil and natural gas. It has made more than $13 billion in capital commitments.