Geostatistics for Seismic Characterization of Oil Reservoirs

Abstract

In the oil industry, exploratory targets tend to be increasingly complex and located deeper and deeper offshore. The usual absence of well data and the increase in the quality of the geophysical data, verified in the last decades, make these data unavoidable for the practice of oil reservoir modeling and characterization. In fact the integration of geophysical data in the characterization of the subsurface petrophysical variables has been a priority target for geoscientists. Geostatistics has been a key discipline to provide a theoretical framework and corresponding practical tools to incorporate as much as possible different types of data for reservoir modeling and characterization, in particular the integration of well-log and seismic reflection data. Geostatistical seismic inversion techniques have been shown to be quite important and efficient tools to integrate simultaneously seismic reflection and well-log data for predicting and characterizing the subsurface lithofacies, and its petro-elastic properties, in hydrocarbon reservoirs. The first part of this chapter presents the state of the art and the most recent advances of geostatistical seismic inversion methods, to evaluate the reservoir properties through the acoustic, elastic and AVA seismic inversion methods with real case applications examples. In the second part we present a methodology based on seismic inversion to assess uncertainty and risk at early stages of exploration, characterized by the absence of well data for the entire region of interest. The concept of analog data is used to generate scenarios about the morphology of the geological units, distribution of acoustic properties and their spatial continuity. A real case study illustrates the this approach.

Bayesian stochastic inversion with petro-elastic relation to quantify thin gas sands of Khadro Formation, Zamzama gas field

“…In Fig. 7c at Zamzama-03, a subsurface earth model is developed that generates synthetics after being forward modeled and depicts a strong correlation with recorded seismic at 5°, 15°, and 25° angles (Soares and Azevedo, 2018).…”

Probability elicitation using geostatistics in hydrocarbon exploration

“…The last approach is called Basin and Petroleum Systems Modeling [16] and is available in commercial software. Seismic inversion techniques are also useful resources for the conception of facies models needed in the workflow [31][32][33]. In [31,32], the concept of sand probability can be directly related to the facies models.…”