Application Of 3D Structural Modeling Workflows To Map, Quantify And Predict Subsurface Permeability Anomalies

Abstract

Two case studies from the petroleum industry are presented, to explain workflows in quantitative structural modeling and how these models can be used to quantify fluid volumes and to predict fluid pathways in the subsurface. The first example is from Colombia and the second one from Hungary. Depending on the observation scale, all subsurface reservoirs are heterogeneous in terms of conductivity or transmissibility. Typical elements causing these permeability anomalies are facies changes, faults (compartmentalization), fracture networks and diagenetic effects (mineral precipitations). According to the data quality, their location, geometry and impact on permeability can be confidently mapped by structural modeling workflows. In the first case study, a 3D structural model of a highly complex oil field in Colombia is presented, producing from fractured Cretaceous sandstones and limestones. The model was built using 3D seismic, well data, log data, surface geology and fluid test data. Using image logs and core data, a detailed fracture mapping of the field was conducted, including cluster analysis. Fracture parameters such as orientation, spacing, open versus closed attitude, fracture porosity and fracture conductivity (under the present stress-field) were mapped across the field. Subsequently, these fracture characteristics were exported into a dynamic reservoir model and a good history match was obtained, allowing for better field development strategies and improved recovery factors. The second case study, located in Hungary, represents a fault-seal analysis of prospects in Pannonian clastic sediments. Based on 2D seismic, newly reprocessed 3D seismic, well data and Gamma Ray logs, a number of prospect-scale 3D models were constructed and the fault transmissibility analyzed in each one of them. The following parameters were assessed: Fault orientation, vertical throw, Allan diagrams, lithological juxtaposition, shale gouge ratio and clay smear potential. Based on these mapped parameters, a correct pre-drill prediction of fault-cross leakage zones versus sealing portions was obtained. In summary, detailed 3D structural modeling workflows – which are traditionally used in petroleum exploration and development or mining – can contribute to localizing and quantifying permeability anomalies in the subsurface. Cellular models with porosity and/or permeability attributes of (gas, oil or water) reservoirs can be used directly for input into dynamic fluid simulation software. These workflows can, therefore, help to significantly reduce uncertainties in fluid modeling and minimize associated operational risks.

AAPG Datapages/Search and Discovery Article #90346 ©2019 AAPG European Region, 3rd Hydrocarbon Geothermal Cross Over Technology Workshop, Geneva, Switzerland, April 9-10, 2019