The Integrated Approach to Reservoir Evaluation - Myths and Realities
Authors: Poggiagliolmi Elio 
Published: October 2008

In reservoir evaluation and development, the assessment of petrophysical properties such as porosity, mineralogy and type of pore fluid, are normally supplied by the available borehole information (well logs, well test and core data). These measurements are generally accurate in the depth direction but large errors are introduced by interpolation between and extrapolation from well locations. In contrast, surface seismic measurements are laterally continuous but are of lower vertical resolution and provide acoustic rather than petrophysicrd information. Total integration of both borehole data and surface seismic data by a multi-disciplinary team is a more cost effective and productive method of reservoir evaluation than the conventional isolated piecemeal approach. his possible to calculate reliable quantitative petrophysical measurements from seismic traces by advanced techniques while maintaining connection back to the physics of the original measurements and without the necessity of employing geostatistics to "guide" the solution. Two case histories illustrate the results obtained by adopting a fully integrated, advanced approach to reservoir evaluation: a 3-D sandstone example with analysis beginning from stacked migrated seismic data and a 2-D carbonate example with analysis beginning from seismic field tapes. Both case histories result in enhanced resolution and in measurements of acoustic porosity from seismic traces.

Introduction

There is general consensus among oil and service companies that total integration of all available data by a multi-disciplinary team is a more cost effective and productive method of reservoir evaluation than the conventional isolated piecemeal approach. To this end, multidisciplinary teams formed to work on specific fields are a common occurrence. These learns are composed of individuals that not only belong to different disciplines but also to different cultures.

"Brainstorming" sessions are often considered the most effective means to promote communication, by breaking down culture barriers and encouraging interdisciplinary cross-fertilization. Unfortunately, brain storming can be at best a palliative became most of the effort by team members is dedicated to carrying out the tasks related to their specific area of expertise. For example, rhe geophysicist deals with the various aspects of seismic data, the log analyst with borehole data, etc. These tasks are normally carried out independently and with a minimum of communication and interaction among the team members. Often the segregation of tasks is attributed to the lack of integrated software and insufficient knowledge of disciplines outside the individual's area of expertise.

A typical example, resulting from this segregation of tasks is the use of 3-D surveys. Normally, these are used to obtain accurate geometric definition of the reservoir - a task with which the geophysicist feels very much at home! However, the full potential of 3-D to obtain a quantitative knowledge of the porosity, fluids and lithological distribution is very much neglected, since this will involve not only seismic, but also the contribution from log analysts, petrophysicists, geologists, and engineers. Such contribution must not be a collection of piece meal results by team members, e.g. structure maps, geological models, formation evaluation results, etc. For integration to be meaningful, it must start from raw measurements with each member of the team working together throughout all stages of the data processing.