文摘
Maximum allowable wellhead pressure is an effective indicator for both site safety control and government regulation of CO2 geological storage projects. In many carbon capture and storage (CCS) projects, the injection rate may also be set as an obligatory objective. For such a problem of multi-objective design, no systematic design methodology has been opened in the publicly available literature. Although a numerical simulator can be employed to obtain the wellhead pressure through a series of trial processes of calculations, this will usually need more model parameters and a large number of computations, especially when there are more reservoirs. In this study, an extensible methodological framework for designing a maximum allowable wellhead pressure for CO2 injection was developed. The methodology is based on a thermal-hydraulic coupling model of wellbore and reservoir flows suitable for arbitrary number of reservoirs. The new methodology can automatically accommodate multiple design objectives, such as site stability and total injection rate. As a result of explicit solutions employed, the methodology has the advantage of less computation and high speed. Using this method, we recommended a maximum allowable wellhead pressure of 13.0 MPa for the Shenhua CCS demonstration project in China, which has been accepted by the expert committee of the project. The large amount of verification data and four-year successful injections in the project have proved the effectiveness of the new method.
