About This Item

This article has been peer-reviewed and accepted for publication in a future issue of the AAPG Bulletin. This abstract and associated PDF document are based on the authors' accepted "as is" manuscript.

Editorial Policy for Ahead of Print


Cite This Item

Display Citation

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Visit Publisher's Website  

Ahead of Print Abstract

AAPG Bulletin, Preliminary version published online Ahead of Print 15 February 2026.

Copyright © 2026. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/02102625067

Complex filling histories for most conventional reservoirs revealed by Quantitative Diamondoid Analysis

Jeremy E Dahl, J.M. Moldowan, Clifford C. Walters, Ye Wang, Tongwei Zhang, and Xun Sun

Ahead of Print Abstract

Plotting the concentrations of some of the least thermally stable Previous HitmolecularNext Hit components in petroleum (biomarkers) versus some of the most thermally stable Previous HitmolecularTop components (diamondoids), a methodology known as QDA, for a large number of oils from different basins around the world reveals a stark contrast between conventional and unconventional oils. With few exceptions, unconventional oils for a particular basin fall on the curve of decreasing biomarker concentration with increasing thermal maturity followed by increased diamondoid concentration due to oil cracking, mimicking the trends observed in laboratory-heated oils. In contrast, conventional oils in most basins, including the most prolific ones, generally plot in a random “shotgun” pattern with no clear relationship between biomarkers and diamondoids. This discrepancy is attributed to differences in the filling history prevalent in the two types of reservoirs.

There is usually very limited migration and mixing of oils in unconventional reservoirs that will disturb the relationship between biomarkers and diamondoids. In contrast, most conventional reservoirs contain complex mixtures due to multiple source rocks and kitchens, along with timing effects. Biomarkers reflect lower maturity charges that represent a fraction of an oil charge ranging from all to only a small fraction. Diamondoids are most abundant in overmature charges that lack biomarkers. Hence, mixed oils (and it is clear from this study that most conventional oils are mixes), of charges that differ in maturity are revealed by analyzing both biomarker and diamondoid concentrations. Furthermore, combining biomarker and diamondoid source correlations using such techniques as Quantitative Extended Diamondoid Analysis (QEDA) and carbon isotopic signatures of individual diamondoids (CSIA-B) allows for a much-improved understanding of oil provenance, migration history and reservoir filling history. This in turn can result in more accurate basin models and the recognition of new plays even in mature basins.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $16
Open PDF Document: $28

AAPG Member?

Please login with your Member username and password.

Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].

Please cite this AAPG Bulletin Ahead of Print article as:

Jeremy E Dahl, J.M. Moldowan, Clifford C. Walters, Ye Wang, Tongwei Zhang, Xun Sun: Complex filling histories for most conventional reservoirs revealed by Quantitative Diamondoid Analysis, (in press; preliminary version published online Ahead of Print 15 February 2026: AAPG Bulletin, DOI:10.1306/02102625067.

Close