Enhancement of CO2 monitoring in the sleipner field (north sea) using seismic inversion based on simulated annealing of time-lapse seismic data.

The primary aim of this research is to enhance seismic data interpretation and CO 2 monitoring by utilizing seismic inversion techniques based on the simulated annealing method. Simulated annealing is a global optimization technique employed for inverting seismic data and provides better results as compared with local optimization-based inversion. This methodology is implemented in the Utsira Formation, located at a depth of 1000 m within the Sleipner Field, Norway. The study encompasses the analysis of three sets of time-lapse seismic data, first from 1994 (pre-injection), followed by surveys in 1999 and 2001, corresponding to the injection of 2.35 million tonnes and 4.26 million tonnes of CO 2 , respectively. Firstly, synthetic data is used to check the reliability of the algorithm followed by real data application. This process starts by performing the inversion analysis on the synthetic data which shows a decrease in the impedance values observed at the injection site whereas the seismic amplitude increases. The qualitative as well as quantitative analysis depicts that the algorithm works satisfactorily. The same process is applied to the real data from the Sleipner field. Acoustic impedances are calculated using a simulated annealing-based inversion scheme for the pre-injection case in 1994 and post-injection scenarios in 1999 and 2001. Because of the presence of injected CO 2 in the years 1999 and 2001, a low impedance zone that ranged from 2000 m/s*g/cc to 2400 m/s*g/cc appeared at the time interval of 0.85–1.10sec. The interpretation of the inverted impedance section and seismic attribute analysis show no signature of CO 2 leakage. The results indicated that the inverted section which is derived from the SA optimization technique shows very clear CO 2 information offering a more realistic representation with enhanced resolution of the CO 2 plume and its migratory paths. • The study developed a methodology for enhanced CO 2 monitoring of time-lapse seismic data. • The methodology uses seismic inversion based on simulated annealing, and compared with traditional methods. • The developed method provides very high-resolution subsurface information and hence CO2 movement. • Finally, the methodology is applied to the Sleipner data and CO 2 leakage has been detected with a very high confidence level. [ABSTRACT FROM AUTHOR]