1 D Maturity Modelling -- Introduction.pptx

Petroleum System Modelling

1. 1-D Maturity Modeling An Introduction to the Technology

2. What is 1-D Maturity Modeling? A model of the geological history in a single well or pseudowell through time Reconstructs burial and erosional history using appropriate stratigraphic subdivisions and lithologies Reconstructs thermal history of rocks Calculates maturity (e.g., vitrinite reflectance), HC generation, expulsion, & cracking

3. Regional 1-D modeling Multiple wells and/or pseudowells No interaction among modeled locations

4. What physical processes can 1-D maturity modeling consider? Deposition and erosion Compaction Vertical conduction of heat Storage or release of heat due to heat capacity effects Heat-flow variation through time Radiogenic heat production (Intrusion of volcanics or diapirs) Generation, expulsion, & cracking of hydrocarbons

5. What physical processes does 1-D maturity modeling not consider? Lateral conduction of heat Fluid flow (groundwater, hydrothermal, HC migration) Convective heat transfer

6. Additional limitations Time scale: cannot model events of very short duration, even if they are known exactly (and very brief events are usually poorly constrained). Predicting reservoir porosity: models not designed for this purpose. Fine-scale features: models create average values for properties of each rock unit, and do not model detail on a finer scale. Fracturing: models do not predict fractures or directly model properties of fractures. They can, however, simulate some effects of fractures. Tectonic subsidence: models do not predict tectonic subsidence. Subsidence is controlled by observed sediment thickness and water depth, not by theory.

7. How does 1-D modeling differ from 2-D/3-D modeling? 2-D/3-D modeling allows lateral heat flow 2-D/3-D modeling allows fluid flow in all directions (pressure, compaction, groundwater, hydrothermal, HC migration) In 2-D/3-D modeling all locations are connected and capable of interacting Focus of 2-D/3-D modeling studies is on migration and trapping 2-D/3-D modeling has much greater data requirements 2-D/3-D modeling requires more time and money

8. 1-D Maturity Modeling Why do we do it? To model maturity and generation as an aid in exploration decisions To provide the geological and thermal foundation for 2-D/3-D modeling of HC migration To learn about geologic history and to integrate data and concepts from different specialties (e.g., tectonics and sedimentology)

9. 1-D Maturity Modeling How do we do it? Software (BasinMod, PetroMod, Genesis, Genex) Series of tasks: Data gathering Model building Model calibration (optimization) Addition of pseudowells Final simulations Reporting of results Documentation of conceptual model, assumptions, & input data

10. Data Gathering Data are critical to success of modeling Geologic data to build models Calibration data Geochemical data for source rocks Data must be sought out – with effort! Careful quality control of data Erroneous geological concepts Outdated information (e.g., old stratigraphy) Bad measured data Bad data are worse than no data

11. Minimum data required to build models Depths of tops and bottoms of all rock units to be modeled Names of all rock units Ages of tops and bottoms of all rock units Lithologies and petrophysical properties of all rock units Amounts of erosion during each unconformity Depositional ages of top and base of missing rocks Lithologies and petrophysical properties of missing rocks Ages of beginning and end of all erosional events Ages of beginning and end of all hiatuses Surface temperatures through time, including present day Heat flow through time, including present day

12. Additional data required to build geohistory models (recommended) Present-day water depth or elevation above sea level Paleowater depths and elevation above sea level

13. In order to model hydrocarbon generation, we must also have… Identities of source rocks TOC values for each source rock (if absolute quantities of hydrocarbons are desired ) Kinetic parameters for each source-rock kerogen

14. Calibration data are highly desirable Measured porosities Pressure data Measured subsurface temperatures Measured heat flows Thermal indicators (paleotemperatures) Vitrinite reflectance (Ro) or equivalent Fission-track data

15. Optimization (Calibration) Compare calculated values with measured values If they do not agree, adjust model until an acceptable fit is achieved Measured data must be reliable Adjusted input data must be geologically and scientifically reasonable Regional optimization made after optimization of individual wells

16. Optimization is carried out in steps Porosity (and ?pressure ) Present-day temperatures Paleotemperatures