Integrated charge and seal assessment in the Monagas fold and thrust belt of Venezuela

Abstract

A B S T R A C TConventional basin and petroleum systems modeling uses the vertical backstripping approach to describe the structural evolution of a basin. In structurally complex regions, this is not sufficient. If lateral rock movement and faulting are inputs, the basin and petroleum systems modeling should be performed using structurally restored models. This requires a specific methodology to simulate rock stress, pore pressure, and compaction, followed by the modeling of the thermal history and the petroleum systems. We demonstrate the strength of this approach in a case study from the Monagas fold and thrust belt (Eastern Venezuela Basin). The different petroleum systems have been evaluated through geologic time within a pressure and temperature framework. Particular emphasis has been given to investigating structural dependencies of the petroleum systems such as the relationship between thrusting and hydrocarbon generation, dynamic structure-related migration pathways, and the general impact of deformation. We also focus on seal integrity through geologic time by using two independent methods: forward rock stress simulation and fault activity analysis. We describe the uncertainty that is introduced by replacing backstripped paleogeometry with structural restoration, and discuss decompaction adequacy. We have built two end-member scenarios using structural restoration, one assuming hydrostatic decompaction, and one neglecting it. We have quantified the impact through geologic time of both scenarios by analyzing important parameters such as rock matrix mass balance, source rock burial depth, temperature, and transformation ratio.Ralf Littke received his diploma in geology and Ph.D. at Ruhr-University Bochum (Germany). He is professor of geology and geochemistry of petroleum and coal and currently dean of the faculty of Georesources and Material Science at RWTH Aachen University. His research interests include sedimentary basin dynamics, petroleum and source rock geochemistry, porosity and permeability of lowpermeability rocks, natural gas geochemistry, organic petrology, petroleum system modeling, and petroleum geology.

Features of geological structure and formation of oil & gas deposits in the Vuktyl thrust fault region

“…Modern software programs of basin modeling allow simultaneously studying a number of processes from sedimentation and immersion to kerogen maturation and multiphase fluid flow [4][5][6][7][8][9][10][11][12][13][14][15][16]. Today there is a fairly large number of basin modeling software programs.…”

Basin and petroleum system modelling of the East Coast Basin, New Zealand: a test of overpressure scenarios in a convergent margin

“…Typically, 2D basin and petroleum system models use an event‐stepping method where sediments undergo layer‐by‐layer backstripping to determine an estimated initial thickness and basin geometry for subsequent use in forward modelling (Hantschel & Kauerauf, ). In regions where there have been significant horizontal offset of layers on faults, however, the event‐stepping method leads to incorrect modelling of palaeo‐geometry (Neumaier et al ., ). Additionally, event‐stepping models cannot be used in thrust‐faulted environments where a single horizon is duplicated along the z ‐axis of the model grid due to computational limitations.…”

“…To avoid these problems, a palaeo‐stepping model was used for this study. Palaeo‐stepping models require the user to specify basin geometry though time (Hantschel & Kauerauf, ), and are the only type of model that can handle complex thrusting geometries (e.g., Gusterhuber et al ., ; Neumaier et al ., ). In this case, the horizon and fault geometries reconstructed in Dynel 2D® were used as direct input for palaeo‐basin geometries for each time step.…”

Assessing the implications of tectonic compaction on pore pressure using a coupled geomechanical approach

“…Because accuracy is crucial, several techniques are commonly used in combination to reduce uncertainty in predictions. Two main approaches are used for pore pressure prediction: (1) porosity-based methods which depend on rock property relationships and the analysis of the trends with depth (Van Ruth et al., 2002;Yang and Aplin, 2004;Bera, 2010;Zhang, 2011) and (2) forward basin modelling (Schneider et al, 1996;Bekele et al, 2001;Schneider and Hay, 2001;Bolås et al, 2004;Allwardt et al, 2009;Hantschel and Kauerauf, 2009;Neumaier et al, 2014), which provides numerical simulations of different physical and chemical mechanisms of overpressure generation and dissipation during basin evolution and therefore is capable of capturing pore pressure history over geologic times. The main limitation of both approaches is that the adopted mechanical compaction models are unidimensional and based on the vertical effective stress.…”