Liberia’s Onshore Oil Prospect: Seep Confirmed in Bassa Basin, Awaits Lab Verdict

NOCAL Technicians at Discovery Spot

MONROVIA, Liberia | December 4, 2025 – Liberia’s long-dormant onshore oil frontier is back under scrutiny. The National Oil Company of Liberia (NOCAL) confirmed this week that its technical teams and partners from the Liberia Petroleum Refining Company (LPRC) have documented a hydrocarbon seep in Nevren Tan, Beon Town, Grand Bassa County, approximately 7.6 miles inland from the Atlantic coastline.

The sighting is situated within the long-recognized onshore Roberts–Bassa Basin. NOCAL stated it has completed two field reconnaissance missions, including surface geology assessments and baseline data collection, and has transported samples for detailed laboratory analysis. The event provides the most tangible evidence to date of a working petroleum system onshore, but it remains strictly a geological indicator, not a commercial discovery.

Historical Context Validates Exploration Trend

Interest in the Liberian coastal plain has cycled through exploration phases for over five decades, primarily driven by the region’s position along the West Africa Transform Margin, geologically analogous to the productive basins of South America. The foundation of the current investigation rests on established technical work:

• Classic Basin Mapping: U.S. Geological Survey (USGS) reports from the late 1960s and early 1970s first mapped the Roberts and Bassa basins, identifying them as discrete sedimentary structures containing Cretaceous-age rock formations like the Farmington River Formation, which holds potential reservoir quality [USGS Open File Report 69-318].

• Early Drilling Cycles: During the late 1960s and 1970s, companies including Union Carbide and Chevron were granted exploration licenses, resulting in several shallow wells drilled offshore. While these initial wells were deemed non-commercial, they did encounter source rock and reservoir quality sandstones, confirming the prerequisites for a petroleum system were present [LPRA Exploration History].

• Simba Reconnaissance (2010): The onshore play gained traction when Simba Energy Inc., holding the Hydrocarbon Reconnaissance License NR-001, used airborne gravity and magnetic surveys to identify multiple oil seep occurrences across its license area. These seeps suggested hydrocarbons were actively migrating to the surface [Simba NR-001 documentation].

• Advanced Geophysical Imaging: Following the initial seep confirmation, the license holder contracted Bell Geospace to fly Full Tensor Gravity Gradiometry (FTG) and magnetic surveys over the 2,962 sq. km coastal strip in 2017–2018. The purpose of this specialized airborne work was to generate 3D subsurface imaging, allowing geologists to map basement structures, define potential fault-bounded traps, and optimize placement for any subsequent seismic acquisition [Bell Geospace FTG survey announcements].

• Official 2025 Verification: The current NOCAL/LPRC mission confirms the geological and stratigraphic alignment of the Nevren Tan seep with these historical basin patterns. The technical team focused on rigorous baseline sampling and established a clean chain of custody for lab analysis [NOCAL Press Update].

Seep is a Signal, not a Solution

For veteran geoscientists, a seep signifies the existence of an active petroleum system: there is a source rock that has matured, and a migration pathway has successfully channeled fluids. However, it does not confirm a commercial discovery.

The critical geological questions for the Roberts–Bassa Basin now focus on the trap integrity and the volume of the charge.

1. Source Depth and Maturity: Does the source rock lie deep enough beneath the basin center to have reached the high pressure and temperature conditions required to generate thermogenic (high-quality) light crude, or is the fluid the result of shallow, localized generation and subsequent biodegradation? Only high-resolution biomarker analysis can resolve this.

2. Trap and Seal Risk: The fundamental challenge in any seep environment is that the best possible discovery has been partially or completely lost. The existence of the seep confirms the seal has been breached along that particular migration path. Geophysical data (FTG, magnetic surveys) can map structures, but only focused seismic acquisition can confirm the presence of an intact seal—a continuous, impermeable caprock—that has successfully trapped a viable volume of hydrocarbons nearby. Without seismic and subsequent drilling, the risk remains substantial.

The Laboratory Mandate

The samples are now undergoing a precise laboratory program designed to de-risk the play by providing a molecular fingerprint of the fluid. The key tests and their function are:

• API Gravity Determination: Measures fluid density. High API gravity indicates lighter, high-value crude; low API suggests heavy crude. The co-analysis of sulfur content will classify the oil as "sweet" (low sulfur, cheaper to refine) or "sour."

• GC-MS Biomarker Profiling: This gas chromatography and mass spectrometry work analyzes specific hydrocarbon molecules (biomarkers) to determine the molecular signature of the oil. This test will definitively establish the source rock type and the thermal maturity, allowing for correlation with known, successful offshore systems.

• Stable Isotope Ratios: Analysis of carbon (\delta^ {13} \text{C}) and hydrogen (\delta\text{D}) isotopes provides a high-confidence metric for distinguishing between genuine, deeply sourced crude oil and shallow microbial gas or modern anthropogenic contamination.

Managing Expectations and Information

The NOCAL press release correctly issued a cautionary note, urging government entities and media to avoid circulating unverified or speculative information until the technical evaluations are complete. This approach is essential for maintaining investor credibility in frontier exploration settings.

Moving forward, NOCAL and LPRC should adopt a communications strategy defined by precise, measured language:

• Line 1 (Validation): "The documented seep validates the long-standing geological hypothesis that an active petroleum system exists in the Roberts–Bassa Basin, confirming its generative capacity."

• Line 2 (Process): "We are currently relying on advanced geochemical tests, including biomarker analysis, to definitively fingerprint the oil's source and maturity. These results guide all further exploration planning."

• Line 3 (Threshold): "A commercial resource requires a proven volume of hydrocarbons trapped beneath an intact seal. The presence of a seep confirms migration, but not a successful trap. Our focus remains on confirming trap integrity."

The outcome of the lab work will narrow the range of possibilities. If the fluid is confirmed as a mature, low-sulfur oil correlating with regional source rocks, it will trigger the justification for a costly, high-resolution seismic program over the structural targets mapped by the previous FTG survey. If the samples prove to be highly biodegraded or non-thermogenic, the onshore prospect will likely be downgraded, and exploration focus will remain on the existing deep-water tracts.

The next definitive phase of the Liberian oil prospect is now technical, not anecdotal. It requires patience pending the forensic results from the laboratory.

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