GLIAG · PETROLEUM & ENERGY INSIGHTS · WORKING PAPER DIGEST

The Trap Does Not Ask What You Assumed

Why oil, gas and pore volume in the Guyana–Suriname Basin can no longer be assessed apart from one another

By Drs. M.P.T. Chin-A-Lien, MBA, M.Sc., Ing. Geologist · Founding Partner & Chief Architect, GLIAG N.V.
Certified Professional Geologist Nr. 5201-1996 (AAPG) · Chartered European Geologist Nr. 92-1996 (EFG) · Energy Negotiator, June 2021 (AIEN)
GLIAG-TECH-2026-DPS-001 · 3 August 2026

For two decades, prospect volumetrics in the Guyana–Suriname Basin have been reported as though pore volume were the only real uncertainty — as if the question that mattered was simply how large the trap is. Nineteen wells, drilled between 2019 and 2026 across Blocks 52, 53 and 58, say otherwise. They describe a basin that is not one province but several, that does not produce one fluid but a spectrum, and whose recoverable volume at trap scale is decided by something subtler than size: the coupled interaction of what arrives, what holds it, and what lets it go.

That fluid spectrum runs the full range of what a kitchen can offer. Twenty-five degree API biodegraded oil surfaces at Bonboni-1. Volatile oil and retrograde condensate appear at Sapakara South-1, Krabdagu-1 and Kwaskwasi-1. Near-dry gas conditions are recorded at Maka Central-1. This is not a set of separate accidents scattered across a licence map. It is the signature of a single kitchen, still charging, whose expelled fluid changes in a predictable way with maturity, depth and distance from the depocentre.

In a dual-phase basin, charge, trap and seal are not three separate draws in a Monte Carlo model. They are one physical system, and they must be assessed as one.

An Architecture, Not a Map of Blocks

GLIAG’s reading of the basin begins by setting aside the block-by-block inventory of discoveries in favour of an architecture: the source kitchens, the migration fairways, the pressure regimes and the fluid provinces that actually govern where and how hydrocarbons accumulate. Architecture outlives licence rounds. It is the correct unit of analysis for a basin this size, and it rests on three pillars.

Four kitchens, not one

Public geochemistry and thermal-maturity data, calibrated against the DSDP and ODP coring programmes of 1970 and 2003, point to four stacked marine source intervals rather than the single ACT surface that first-order models assume: the proven, world-class Aptian–Cenomanian–Turonian interval; a Late Aptian contributor proven in the western Demerara Plateau and deeper Block 58; an inferred Barremian interval, undrilled but geophysically indicated; and a deep, hot Tithonian interval, increasingly gas-prone toward the outboard basin.

Two ways the oil travels

The same expelled fluids move through the basin under two distinct pressure regimes. Onshore and nearshore, hydrostatic lateral migration carries hydrocarbons some 200 kilometres updip to feed the biodegraded, low-GOR accumulation at Tambaredjo. Offshore, in the Golden Lane proper, deep overpressured vertical fill-and-spill charges turbidite reservoirs in successive pulses, with spill points reset again and again by the interplay of trap geometry and fluid density.

Provinces, not averages

Once the source stack and the migration regime are respected, the basin resolves into distinct fluid provinces — oil-dominant, mixed oil–gas, gas-condensate, dry-gas — and into zones where the outcome is decided by the seal rather than by the charge itself. Any single prospect must be read against this map, not against the nearest discovery’s average.

A Curve, Not a Scatter

Plotted by stratigraphic position, the nineteen-well dataset shows something more disciplined than variability: a continuous, linear relationship between gas–oil ratio, gravity and depth. Bonboni-1 sits at 25° API and a GOR near 300–500 scf/bbl. Sapakara South-1 sits at 34–37° API and roughly 1,100 scf/bbl. Krabdagu-1 records volatile oil at 2,000–2,800 scf/bbl. Kwaskwasi-1 and Maka Central-1 sit at 42–50° API, in retrograde-condensate and near-dry-gas territory. Together these points trace a single kinetic vector, not a scatter — and that vector is the bridge between what the kitchen is producing and what any given trap will be asked to hold, inferred before the drill bit ever turns.

Why Column Height Is an Integration, Not a Subtraction

Four controls, coupled, set the retained column in a dual-phase trap: the charge PVT at the point of entry; the trap’s geometry, closure and spill points; the top-seal’s actual capillary entry pressure for the fluid in question; and the fault-seal capacity for that same phase, since a fault that holds oil will not necessarily hold gas at the same interfacial tension.

Treat these separately and two errors follow, both common in the public record. Assume a black-oil column under a seal whose real capacity, tested against the actual gas phase, is a fraction of what was assumed — and the volumetric is overstated. Assume a gas-only column at a depth where the PVT in fact places the trap in the retrograde-condensate window — and an entire liquid leg disappears from the estimate. Either error alone can move a resource number by a factor of two or more. A rapid check for both: compare the assumed top-seal entry pressure against the interfacial tension the actual PVT would produce, and compare the assumed charge-GOR against the family curve for that depth. A mismatch beyond a factor of two means the number is not defensible.

From Kitchen to Recoverable Barrel: A Documented Mass Balance

Doctrine at trap scale is only credible if it closes at basin scale. The GLIAG reconstruction of the SE Golden Lane kitchen, built on Pepper & Corvi (1995) organofacies kinetics and reconciled to the Staatsolie GeoAtlas 2026 basin-wide balance, cascades as follows:

Cascade step	Value
Generated in-place	1,455 bnboe
Expelled from source	949 bnboe
Trapped after losses	~170 bnboe
Recoverable (total)	~73 bnboe
— oil	26 bnboe
— condensate	18 bnboe
— gas	29 bnboe
Discovered to date	~11% of recoverable
Yet-to-find	~89% of recoverable

The critical moment — the point at which generation, migration and trap formation align — is placed at approximately 45 million years ago, in the Middle Eocene, consistent with the observed trap ages and with the timing evidence embedded in the basin’s downdip flow-test record.

Two Anchors Outside the Basin, One Inside It

No ACT interpretation stands on its own. GLIAG ties the Canje interval to the Querecual and La Luna formations of the conjugate Venezuelan margin — the author’s own 1986 Maracaibo Basin geochemistry work among the calibration points — and to the West African conjugate shelf, to constrain source quality, expulsion efficiency and fluid character independently of the Guyana–Suriname well data itself.

Inside the basin, Tambaredjo does the same work. Its biodegraded 12–18° API oil, sitting 200 kilometres updip of the depocentre, carries the same ACT geochemical signature as the deep-offshore fluids. That is not a coincidence to be noted in passing. It is hard evidence that one connected engine feeds both migration regimes, and it anchors the long-distance migration term in the mass balance to something drilled, produced and measured for decades.

What This Means for How Prospects Get Ranked

• Charge risk belongs against the local source-stack map, not a single ACT surface — a well that looks under-charged in a one-interval model may be correctly charged from a deeper Aptian or Barremian source.
• Fluid type belongs on the GOR–API family curve at the prospect’s own depth, not the average of the nearest discovery.
• Column height belongs to a coupled PVT–capillary assessment, not a pore-volume Monte Carlo run in isolation.
• Seal risk belongs to the phase that actually reaches the seal — a top seal proven against oil is not thereby proven against gas.
• Trap timing belongs against the ~45 Ma critical moment, not against today’s structural map.

The Honest Limit of the Framework

This architecture is built entirely on public data: nineteen wells, the Staatsolie GeoAtlas 2026 balance, DSDP and ODP coring, and the Canje–Querecual–La Luna analogue triangle. That is its discipline and its limit at once. It reaches a screening-plus level defensible before a technical committee. It does not, and does not claim to, replace an FDP-grade evaluation built on confidential 3D seismic, core, PVT and production data. It is the public-domain scaffolding against which such evaluations can be tested for consistency — nothing more, and, done properly, nothing less.

Closing

The Guyana–Suriname Basin will not be decided by the discovery of a new source rock. Four kitchens, two migration regimes and a resolved fluid spectrum are already on the record. What remains is the discipline to read charge, trap and seal as one coupled system rather than three independent guesses — because in a mixed oil–gas trap, that is what they physically are. Deep time built this basin in stacked pulses over a hundred million years. It is only fitting that we assess it the same way: together, not apart.

Soso Lobi.

© 2026 Drs. Marcel P. T. Chin-A-Lien and Golden Lane Investments Advisory Group (GLIAG N.V.). All rights reserved. This essay is adapted from GLIAG Working Paper Rev-02, “Dual-Phase Charge, Column, and Seal in the Guyana–Suriname Basin” (3 August 2026). Published on petroleumenergyinsights.com. No part of this essay may be reproduced, redistributed or used to train, fine-tune or ground any AI/ML system without prior written consent of the author and GLIAG N.V. This is a public-domain screening-level scientific and strategic-advisory contribution; it is not investment advice, a securities recommendation, or a reserves report under SPE-PRMS, SEC Regulation S-K, or NI 51-101.