Possibilities for in-operation control of remaining recoverable reserves at various stages of oil production objects development

Abstract

Estimation of oil recovery factors on the basis of geological and hydrodynamic simulation is very cost- and time-consuming. As a result, re-estimation of recoverable hydrocarbon reserves is performed over long periods of time without any more short-term corrections of estimates. The approved oil recovery factors can become outdated due to the changes in the economic conditions of development or a misalignment between actual development and design conditions. For reliable estimation of remaining recoverable reserves at oil production objects, it is critically important to establish in-operation control of oil recovery factors reliability, including their objective achievability within specific time frames. Based on the example of Perm region oilfields, the paper analyzes the practice of annual geological and financial estimation of the reserves according to international standards. A conclusion has been made that it is necessary to perform similar control of recoverable oil reserves estimated as per the Russian classification. Several options of in-operation control are available for approved oil recovery factors: use of analog-statistical methods, displacement characteristics, production decline rate analysis. The methods are based on various physical regularities, their effectiveness to a large extent depending on the quality of input information and the stage of the production object development, as well as on the economic conditions. Case studies are used to analyze the effectiveness of control of the approved oil recovery factors. For early development stages, use of multivariate analog-statistical dependencies drawn from geological parameters built for specific production objects was found to be the most effective method. The long history of Perm Krai oil fields development and a relatively large number of production objects at late stages of recovery make this statistic approach feasible. At late stages, more reliability can be obtained by using methods based on the displacement characteristics and oil production decline rate taking into account the economic limit of development. The suggested control method involves use of statistic dependencies relying on both geological and technological parameters. Comprehensive use of multiple method approaches helps achieve a more reliable estimation of the remaining recoverable reserves at the production objects.

Keywords

• remaining recoverable reserves
• oil recovery factor
• production object
• oilfield development design
• geological and financial estimation of reserves
• displacement characteristics
• oil production decline rate