Use of a Seismic Derived Constraint: Different Steps and Joined Uncertainties in the Construction of a Realistic Geological Model

Realistic geological modeling can be considered as the first objective in a reservoir characterization workflow. This term describes the process of building static 3-D reservoir models based on available a priori information, geological interpretations and quantitative geological, seismic, and production data. The definition of the best “realistic geological model” to be produced has to be discussed depending on the target objective: to produce a simulation which honors at best the geological parameters and the seismic derived constraints or to produce a simulation which will fit at best the production data. The incorporation of seismic information is a crucial element in reservoir geological modeling. Many recent research works have focused on the introduction in probabilistic models of secondary data characterized by a relationship, often indirect, with the reservoir properties. Due to the different scales of resolution between seismic and geology and to the complex relationship between rock properties and seismic response, a logical process can be to firstly extract geological properties from seismic data and second to constrain the facies simulation using these properties. The extraction of soft geological information from seismic data relies on statistical calibration with well data. Mainly two approaches can be used, either based on supervised segmentation or on estimation techniques. The obtained information consists in variables correlated with the facies distribution. Depending on the available information the variables can be related to the total thickness of the studied stratigraphic unit (leading to 2D constraints as maps) or to small volumes inside the unit (3D constraints). IFP-CG (Institut français du pétrole - Centre de Géostatistique of the École des Mines) have developed an innovative methodology to generate facies proportions grids from well data, sedimentological conceptual models (maps and zonations), and constrained with seismic derived information. The objective of this paper is to present an analysis and evaluation of the real impact of these seismic derived constraints on the reservoir geological model in terms of quantification of uncertainties, heterogeneities distribution, and key geological characteristics. In the geomodelisation workflow, this work takes place when the structural framework of the reservoir is determined and also when the geological conceptual model is defined in terms of interpretation, environment, and layering. Its purpose is to investigate possible variations in parameterization of the scenarios of filling the space with geological properties. Using a real data case, different constraints and different methods of seismic integration are compared. Their impact of seismic in the framework of the truncated gaussian methodology and compared to the impact of the uncertainty on geological data