Other Non-Mining Operations:
In addition to our mining operations, we operate several subsidiaries which provide auxiliary services for our coal mining operations. Rhino Trucking provides southeastern Ohio coal operations with reliable transportation to our customers where rail is not available. Rhino Services is responsible for mine-related construction, site and roadway maintenance and post-mining reclamation. Through Rhino Services, we plan and monitor each phase of our mining projects as well as the post-mining reclamation efforts. We also perform the majority of our drilling and blasting activities at our company-operated surface mines in-house rather than contracting to a third party.
Other Natural Resource Assets:
Oil and Gas
In addition to our coal operations, we have historically invested in oil and gas mineral rights that have generated prior revenues for us, which helped to diversify our income streams. We have also expanded our business to include infrastructure support services for oil and gas operators, primarily in the Utica Shale region.
We and an affiliate of Wexford Capital participated with Gulfport Energy, a publicly traded company, to acquire an interest in a portfolio of oil and gas leases in the Utica Shale region of eastern Ohio. As of December 31, 2013, we had invested approximately $31.1 million for a 5% net interest in a portfolio of leases in the Utica Shale consisting of approximately 152,300 gross acres, or approximately 7,615 net acres. In addition, per the joint operating agreement between us, Gulfport and an affiliate of Wexford Capital, we funded our proportionate share of drilling costs for wells that were drilled on our acreage, which totaled approximately $23.3 million as of December 31, 2013. We received approximately $5.6 million of revenue from the Utica Shale investment for the year ended December 31, 2013. In March 2014, we completed the sale of our entire Utica Shale joint interest investment to Gulfport for approximately $184 million, which provided us with a substantial return on our initial investment.
In August 2015, we completed the sale of our oil and natural gas investment of approximately 1,900 net mineral rights in the Cana Woodford region of western Oklahoma. We received approximately $5.7 million in proceeds from the sale of the Cana Woodford oil and natural gas mineral rights.
In September 2014, we made an initial investment of approximately $5.0 million in a new joint venture, Sturgeon Acquisitions LLC ("Sturgeon"), with affiliates of Wexford Capital and Gulfport Energy. Sturgeon subsequently acquired 100% of the outstanding equity interests of certain limited liability companies located in Wisconsin that provide frac sand for oil and natural gas drillers in the U.S.
In December 2012, we made an initial investment of approximately $2.0 million in a new joint venture, Muskie Proppant LLC ("Muskie"), with affiliates of Wexford Capital. Muskie was formed to provide sand for fracking operations to drillers in the Utica Shale region and other oil and gas basins in the U.S. In November 2014, we contributed our investment interest in Muskie to Mammoth Energy Partners LP ("Mammoth") in return for a limited partner interest in Mammoth. Mammoth was formed to own various companies that provide services to companies who engage in the exploration and development of North American onshore unconventional oil and natural gas services. Mammoth's companies provide services that include completion and production services, contract land and directional drilling services and remote accommodation services.
Timber Wolf Terminals
In March 2012, we made an initial investment of approximately $0.1 million in a new joint venture, Timber Wolf Terminals LLC ("Timber Wolf"), with affiliates of Wexford Capital. Timber Wolf was formed to construct and operate a condensate river terminal that will provide barge trans-loading services for parties conducting activities in the Utica Shale region. The initial investment was our proportionate minority ownership share to purchase land for the construction site of the condensate river terminal. Timber Wolf has had no operating activities since its inception.
Incidental to our coal mining process, we mine limestone from reserves located at our Sands Hill mining complex and sell it as aggregate to various construction companies and road builders that are located in close proximity to the mining complex when market conditions are favorable. We believe that our production of limestone provides us with an additional source of revenues at low incremental capital cost.