With respect to costs, the Company performed in line with expectations in the first quarter. Upstream capital expenditures were approximately $39 million compared to guidance of $40 million. Adjusted G&A expenses were approximately $9 million, 4% below themid-point of our guidance range for the quarter. Operating expenses for the first quarter werein-line with guidance at approximately $49 million.
Northwest STACK / North Louisiana Operated Drilling Program
Riviera’s operated NW STACK drilling program is progressing on schedule with the Company turning to production 3 wells in the first quarter and 2 additional wells thus far in the second quarter. Early results are encouraging. The average IP15 rate of the first 4 wells is approximately 610 boepd with 43% oil and 65% liquids. All of these wells are single mile laterals with a target capital cost of $5.0 million to $5.3 million, which is expected to generate a 30% to 40% IRR.
The Company also completed a 2 well pad in North Louisiana late in the first quarter. The initial production of these wells is very strong with a choke restricted 2 well average IP30 of approximately 20 MMcfe/d. The expected IRR of these wells is over 100%.
Blue Mountain Business Update
On average for the first quarter of 2019, natural gas throughput was 117 MMcf/d and NGLs produced were approximately 8,700 bpd, compared with 61 MMcf/d and 2,290 bpd for the first quarter 2018. Natural gas throughput volumes for the first quarter of 2019 were lower compared to the fourth quarter of 2018 throughput of 132 MMcf/d as our primary customerre-evaluated their drilling plans. Throughput volumes are expected to increase during the remainder of 2019 as Roan has announced plans to increase average annual production by 30% over 2018.
Management continues to diversify and extend Blue Mountain’s midstream business to best position it for its eventual separation as a standalone entity or for another transaction that maximizes shareholder value.
During the first quarter, Blue Mountain announced its entrance into the produced water management business with the execution of an agreement with Roan to completely handle all their water management needs in the dedicated acreage footprint, including produced water gathering, treating, transportation and disposal. Blue Mountain began providing these services on April 1, 2019.
In addition, Blue Mountain finalized an agreement with a new third-party to provide natural gas gathering and processing services on its Merge system. The agreement carries a long-term acreage dedication with primarilyfee-based revenues and the potential for incremental volumes as drilling activity advances within the dedicated acreage footprint. Management believes the area has significant upside and is in active discussions with several third-party producers to attract incremental natural gas and produced water volumes to its core Merge platform.
Blue Mountain’s adjusted EBITDA for the first quarter of 2019 was flat compared to the fourth quarter of 2018, on approximately 9% decrease in average natural gas throughput over the prior quarter. Adjusted EBITDA remained flat due to tightening of the spread between Conway and Mont Belvieu NGL pricing. Elimination of the basis exposure would have added approximately $2 million to Blue Mountain’s margin in the first quarter of 2019. Management has hedged a material portion of its exposure to the NGL pricing differentials at Conway and Mont Belvieu for 2019 and expects to eliminate all basis dislocation by the first quarter of 2020 when ONEOK’s Arbuckle II Pipeline is completed.
Capital for the first quarter was $21 million, compared with $57 million for the first quarter of 2018. The majority of capital was invested in new well connects in the Merge and construction of water gathering pipelines.
“I’m pleased with Blue Mountain’s performance over the quarter as we made significant strides to diversify our revenue stream going forward. With Roan’s projected volume ramp during the second half of 2019, our water business becoming established moving to our piped system, and other growth prospects in development; I’m excited about our continued evolution becoming a top tier midstream enterprise,” commented Greg Harper, President and CEO of Blue Mountain.