Basin Modeling

Numerical modeling of petroleum systems has been developed since the early 1980's and greatly improved in recent years due to advances in organic geochemistry, multi-phase fluid flow models, numerical methods and computer graphics. Basin modeling has become an essential tool in the exploratory strategy of petroleum companies because it provides a dynamic, objective and integrated view of processes such as sedimentation, compaction, water flow, heat transfer, source-rock maturation, petroleum expulsion, migration and accumulation. Not only does basin modeling allow explorationists to simulate basin evolution and petroleum generation, expulsion and migration in a physically-consistent way but, most important, it also provides significant insights into fundamental questions such as:

1) Where are the effective kitchen areas of the potential source rocks?
2) What is the timing of the processes of petroleum generation, expulsion and migration regarding each source rock level?
3) What are the possible migration pathways from source rocks to reservoirs?
4) What is the role of faults as migration pathways?
5) How effective must drains and seals be in order to have a commercial accumulation in a given geologic context?
6) What are the expected oil and gas composition in a petroleum trap?

Results from basin modeling studies are used to better understand petroleum systems and, most importantly, to identify potential risks in new exploration targets. GSI offers basin modeling services using various commercially-available modeling software, according to the clients' specific needs. For petroleum systems analysis and prospect risking, GSI uses the Trinity/Genesis/KinEx petroleum systems toolkit developed by Zetaware, Inc.

For more information, visit the Zetaware website at www.zetaware.com.




Hydrocarbon charge is a key consideration in developing and maturing prospects and leads. For a prospect to be charged with economic quantities of oil and gas, a series of essential elements and processes must occur in space and time, which collectively are referred to as a petroleum system. These include the existence of source, reservoir, seal and overburden as well as hydrocarbon generation-migration-accumulation along with trap formation.

In areas where a petroleum system is already indicated by known oil and gas fields, charge risk is diminished. Still, to ensure that a prospect is not located in a high-risk sector of the basin or in a migration “shadow”, pre-drill charge assessment using a combination of geochemistry and petroleum systems modeling is a cost-effective technical approach. Some of the questions addressed are:

Has the prospect received economic quantities of oil and gas?

If so, what are the most likely volumes?

Are there single or multiple source horizons?

Where are the “kitchen” (source) areas?

What is the timing of the charge event(s)?

What is the expected charge phase (oil and/or gas, GOR)?

Which elements/processes most affect charge volume estimates?

Is adverse oil quality a tangible risk?

Geochemical Solutions International (GSI) is pleased to add prospect charge risking to its upstream technical services. The following describes several important aspects of this technology.


Oil, source rock and seep geochemistry can be used in conjunction with petroleum systems modeling to quantify risk associated with hydrocarbon charge. Oils and seeps are geochemical derivatives of their source rocks, and information from oil geochemistry (source type, age, maturity, kerogen quality) can be used to identify and geographically-delineate the regional extent of individual petroleum systems.



Similarly, basic source-rock screening tools such as Total Organic Carbon (TOC), Rock-Eval pyrolysis and vitrinite reflectance measurements are used to map regional source rock richness, lateral source variations and degree of thermal evolution.

Petroleum systems modeling can be used to integrate these diverse geochemical data with structural, stratigraphic and lithologic data, thermal geohistory information, and engineering data. A petroleum systems model is a digital data model of the complete petroleum system in which the interrelated elements and processes can be simulated in order to better understand and predict them. The resulting simulations yield information for practical decision-making, such as identification of hydrocarbon “kitchens” that can charge a prospect, direction and timing of migration and estimates of charge volume and phase.

GSI has extensive experience in the identification and delineation of petroleum systems elements that serve as constraints for charge models. GSI has conducted oil, seep and source rock regional studies globally, encompassing nearly all Brazilian sedimentary basins, as well as Argentina, Peru, Trinidad, Cuba, the Gulf of Mexico and West Africa.


Either 1D (single-point), 2D (geologicsection based), or 3D (grid-based) models can be used for charge risking. Each technique has its respective merits, however only 3D models allow calculations of charge volumes and estimations of fetch or “drainage” areas based on structural constraints. These are important in understanding charge at the prospect scale.

For this reason, GSI recommends a 3D approach whenever there is adequate subsurface data coverage. 1D modeling can be used for thermal and lithologic calibration of the 3D model and to better understand individual petroleum system processes (source, maturation, expulsion, migration). Where data coverage is insufficient for a 3D model, multi-point 1D models or 2D models are alternatives.



3D geologic models are based on depth-converted, chrono-stratigraphic map grids. A minimum of three map grids are necessary for prospect charge modeling: surface (or mud line), the prospect interval, and the source rock interval. In practice, the more stratigraphic horizons that can be reasonably incorporated into the geologic model, the better. In addition to the prospect area, the geographic extent of the grids must cover the expected source “kitchen” area and the migration fairway. Other geologic data, such as fault traces or lithofacies data can also be included.

The following table summarizes the data types and formats required to develop a 3D charge model.



Most prospect charge models are developed working one-on-one with exploration geologists and geophysicists. Typically, GSI will build a preliminary geologic model from the input data provided. During this initial phase, some questions may arise regarding the stratigraphic data, and some editing of the map grids is common.

Once the geologic model has been “polished”, some trial simulations will be carried out and the results reviewed with the geologist or geophysicist. This generally results in some changes to the model parameters (variations in thermal gradient, source rock richness or lateral extent, nature of carrier beds). The process is iterative until a satisfactory result is attained.



Prospect charge models we have conducted generally require two to six weeks from receipt of input data to delivery of final data product, depending on the number of leads modeled and the complexity and level of detail addressed.


The results are usually summarized in a powerpoint presentation containing structural maps and graphs that illustrate the charge scenario(s) for the prospect. Examples of typical data products are shown in this document.

Digital grids of modeled properties (e.g., oil or gas expelled) or vector files (e.g., spider diagrams) suitable for importing to internal maps or seismic projects can also be provided.



The cost to develop a 3D charge model varies according to the level of simulation detail, the number of “what-if” scenarios incorporated, and the total number of leads or prospects modeled. Generally, the minimum cost to develop and report a result that satisfies most objectives is approximately $15,000 USD. Beyond that, cost will vary according to a fixed man day-rate that is established in advance. Similar cost estimates apply to development of 2D models; 1D models are generally lower in cost.