Application of the Recovery Curve Method to Petroleum Reservoir Material Balance Calculation

Research output: ResearchDoctoral Thesis

Organisational units


The dissertation presents the very first application of Mittermeir’s material balance method to a real naturally fractured reservoir (NFR). The author of this dissertation proved and gave clear evidences about the theoretical correctness and practical viability of this new method. The work should be seen as the integration of 10 years research and development efforts conducted at the Montanuniversität Leoben and at the Sharif University of Technology, Tehran. In 1936 Schilthuis published for the first time a material balance (MB) approach for oil and gas reservoirs. MB is still one of the basic, analytical tools for analyzing recovery mechanisms, for determining the hydrocarbons in place and the water influx. For almost 80 years no MB method fully accounting for the matrix-fracture fluid transfer was offered. From this reason, up to now, the applicability of the MB methods to NFRs remained limited. The new MB method, used in this work fully considers the physics of the matrix-fracture interaction, and thus the matrix oil recovery process. To make it generally applicable a specialized workflow was developed. Instructions were given how to use the field data, respectively, how to proceed in case if the data is incomplete and uncertain. For NFRs, most of the oil is stored in matrix blocks acting as fluid sources/sinks to the surrounding fracture planes, in which fluid transport and production/injection takes place.The MB method is based on the recognition that the performance of water and gas displacement from matrix blocks can be depicted in the form of recovery factor versus time. These recovery curves determine the matrix-fracture oil transfer. A close relationship between the recovery curves and the observed reservoir state (pressure, position of the phase contacts, water cut, GOR, etc.), the aquifer parameters and the matrix-fracture oil transfer exists. The applied MB method matches both the reservoir pressure and the positions of the phase contacts. It also provides aquifer and matrix-fracture fluid transfer models. Applying the parameters of those models in prediction mode and assuming a future production strategy, reservoir pressure decline and phase contact movements can be forecasted. The entire workflow and calculation scheme were presented based on the Sabah reservoir, located in the Libyan Sirte basin. It contained more than 500 MMstb original oil in place. Sabah has 35 years production history, is heavily fractured and produced through 70 wells. The aquifer inflow and the optimal analytical aquifer model was determined by matching the pressure history. Recovery curves were assessed by fine scale numerical modelling. Its plausibility was verified with the field’s production profile. The phase contact history was successfully matched by tuning the beforehand determined recovery curve. The feasibility of a future water cut decrease and an increased oil production was demonstrated in forecast calculations. For Sabah reservoir the practicability and benefits of this dual porosity MB could be clearly demonstrated


Original languageEnglish
StatePublished - 2015