An Enhanced Resource Classification – A Tool for Decisive Exploration

Abstract

The classification of resources, both undiscovered and discovered, is becoming increasingly important in the decision making process of major oil companies. Statoil has developed a new internal resource classification system to support investment decisions and the management of petroleum assets.

To achieve this goal, resource definitions have been related to the value chain from early exploration to production, and to economic assessments. Each resource class is associated with a typical business action. Both undiscovered and discovered resources are included, with the discovered, undeveloped petroleum assets given a major focus due to their importance in resource management.

The use of the classification system increases the awareness of the quality and consistency of the resource calculations and of the registration of discovered resources. A method of analysing prospects and discoveries according to their different geological segments (fault blocks etc.) has been chosen to achieve a consistent resource assessment. This reduces the possibility of unexpected results, causing significant reductions in the recorded discovered resources.

The estimates of resources are made using probability distributions. In this way the summation of resources by the use of Monte Carlo simulation, is a fast operation and the variance can be estimated. The proven reserves, which we define as a 'low' value with a high degree of certainty (90 percentile), are easy to calculate both within individual fields and for aggregated reserves of many fields.

Statoils new classification system has the following advantages:

– it gives a better description of fields and prospects with uncertain economy.

– it is based on the value chain from unmapped prospects to production

– the categories are linked to typical business actions

– the importance of economy in the system makes it useful for target setting and performance measurements

– the probabilistic distribution of resources within a segment, reservoir, prospect or field makes a statistically correct summation possible

– the use of segmentation of reservoir zones gives a better separation between areas with tested hydrocarbons and areas carrying a risk of being water-bearing, and is the basis for classifying reserves as proved.