Miscible Gas Injection as a Key Development Scenario for the Complex Reservoir with Low Permeability

Abstract

Currently, for the most oil companies it is possible to identify a general tendency that the reservoir permeability for the new prospects is decline. Reserves quality deterioration increases the risk of the future oil production failure. This paper describes the organization of an integrated approach to source data analysis, simulation model constructon and miscible displacement design in a low-permeable reservoir. At the first stage, a reservoir fluid model is constructed. Based on the lack of a qualitative oil sample from the well (original sample was significantly depressurized during testing) and on the analysis of the fluid properties of the analog fields, the prediction of the main oil parameters was made. At the second stage, using static parameters of a low-permeable reservoir, probabilistic simulation models of the field was constructed, providing a coverage of the main spectrum of reservoir uncertainties. Further, import gas resources were estimated for the injection implementation. The main result is an integrated assessment of the impact of uncertainties for oil properties and gas import resources on key economic indicators for a miscible displacement at the field with a low-permeable reservoir using the reservoir simulation model. The analysis verified the key parameters that have the greatest impact on the economy of the project, determined the threshold values for the volume of gas imports, and based on the feasibility study made recommendations on the choice of the pilot area for injection. A program for conducting additional laboratory experiments was also prepared, this study will allow the narrowing of the oil composition uncertainties and its interaction with injection gas. In addition, a program is developed to carry out special core experiments on gas injection, which will make it possible to correct the behavior of phase permeabilities for a miscible displacement. This paper shows that on the basis of reservoir simulation an integrated approach organization for the verification, accounting and analysis of uncertainties on reservoir characteristics, fluid properties and volume of imported third-party gas allows to search for and select an economically viable and sustainable option to develop an oil field using miscible gas injection technology. An implementation of this approach provides a recovery factor increase from 7% to 25%.