The South Marsh Island Block 71 (SM71) is an oil and gas field located in the shallow waters of the Outer Continental Shelf (OCS) of the Gulf of Mexico, US. The field lies in a water depth of 137ft and covers an area of 12.16km2.

SM71 is a joint venture between Otto Energy (50%) and Byron Energy (50%). Otto owns a Net Revenue Interest (NRI) of 40.63%, while Byron Energy holds an equivalent NRI in the project.

The field currently produces from three wells, F1, F2 and F3. First production from the field took place from the F1 well in March 2018, while production from F2 and F3 wells started in April 2018.

Two more wells, F4 and F5, were scheduled to commence production in 2020 and 2021 respectively. Otto opted out of the partnership in the F4 well, giving Byron 100% WI and NRI of 81.25%.

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The production, however, has been postponed due to uncertainty around the world in wake of the COVID-19 pandemic. The wellbore process of F5 well has also been abandoned.

South Marsh Island Block 71 location, discovery and reserves

The SM71 field is located off the coast of Lafayette in Louisiana in the OCS, which is a potential and proven basin for hydrocarbons.

The field was discovered in April/May 2016 by the SM71 F1 well, which was later converted into a production well. Otto farmed into the field and commenced exploration in 2016.

The offshore field is estimated to contain gross reserves between 1.6 million barrels of oil equivalent (Mmboe) and 7.1Mmboe.

Exploration and appraisal on South Marsh Island Block 71

Appraisal on SM71 commenced in December 2017 with the drilling of the F2 well, which was spud by the Ensco 68 jack-up rig. The well encountered four hydrocarbon-bearing sands and net oil pay of 190ft (58m).

A second appraisal well, F3, was also drilled by the Ensco 68 jack-up rig in January 2018. The well reached a total depth of 7,717ft and 211 net feet of oil pay.

The Ensco 68 jack-up rig was also used to complete the three wells for production.

The recent exploration at the F5 well was performed using Enterprise Offshore Drilling Company’s EOD 264 jack-up drilling rig.

SM71 project development and production

SM71 was earlier proposed to be developed through an unmanned platform. The project design was changed and later converted to a manned platform operated by Byron Energy.

The tripod-shaped platform F is the primary production platform for the F1, F2 and F3 wells of the field. Installed in November 2017, it has a processing capacity of 5,000 barrels per day (bpd).

The F1 and F3 wells produce oil and gas from the D5 sand reservoir, while the F2 well produces from the B65 sand reservoir area. The reservoirs have good aquifer support and low sovereign risk.

In 2017, a 500ft-long, 4in diameter pipeline for oil and a 7,000ft, 6in diameter pipeline for gas were installed at the site area.

SM71 produces high-quality Louisiana Light Sweet crude (LLS). Approximately, 1.5 million barrels (mmbbl) of oil and two billion cubic feet (bcf) of gas was produced during the first year of production in 2018/19.

Contractors involved

Byron Energy signed an agreement with WesternGeco, a Schlumberger subsidiary, to add additional licensed 3D seismic data to its in-house data inventory and to implement high effort seismic data processing over the SM71 project area.

EOD was awarded a drilling contract to use EOD 264 rig in November 2019.