Under the terms of the agreement, Oneok Partners will acquire 80% stake in the West Texas LPG Pipeline Limited Partnership (West Texas LPG) and 100% interest in the Mesquite Pipeline (Mesquite).

The two units have approximately 2,600 miles of NGL gathering pipelines extending from the Permian Basin in southeastern New Mexico to East Texas and Mont Belvieu, Texas.

Oneok Partners president and chief executive officer Terry Spencer said: "With this acquisition, along with other announced capital-growth projects in North Dakota, Oklahoma and Wyoming, the partnership’s total investment has increased by more than $3 billion in the last year.

"Acquiring these natural gas liquids pipelines allows us to continue to serve producers in the Permian Basin and other multiple high producing NGL-rich basins, including the Williston Basin, the Powder River Basin, and the Cana-Woodford and SCOOP plays in Oklahoma.

Upon completion of the transaction, Oneok Partners will operate both the pipelines while the remaining 20% of West Texas LPG will be owned by Martin Midstream Partners.

"These assets will provide fee-based earnings to the partnership and further expand our natural gas liquids segment’s portfolio of assets while positioning us for additional growth opportunities," Spencer said.

The two pipeline assets are expected to generate approximately $40m in annual adjusted earnings before interest, taxes, depreciation and amortization (EBITDA) in 2014.