Processing and data analysis of time-lapse microgravity due to ground water level changing in baseline stage of CO2 injection

2nd Southeast Asian Conference on Geophysics

Darmawan, Noviandi^1 ; Wahyudi, E.J.^1 ; Kadir, W.G.A.^1 ; Sule, R.^1

Institut Teknologi Bandung, Indonesia^1

关键词: Acquisition process;    Average values;    Drift effects;    Gravity data;    Gravity survey;    High-accuracy;    Long term drift;    Reference stations;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/318/1/012020/pdf
DOI  :  10.1088/1755-1315/318/1/012020

来源: IOP

【 摘 要 】

Monitoring stability of the field in research area using time-lapse microgravity method has been done with data acquisition process in 2014 and 2016. This method requires high accuracy in μGal units. Since we use relative gravimeter, drift performance from instrument is also influential to the data significantly. In this paper we conducted reprocessing data using closer reference station from research area thus the drift effect cause by mobilitation time and duration of instrumental resting can be reduced. In conditions prior to injection, ideally the change in gravity value in the area would be very small with the assumption of the absence of injection activity. However, after the processing data stage we can see time-lapse microgravity anomalies within the range of ± 80 μGal. This anomaly was assumed occurred by instrument effect (typical for spring sensors) in field measurement and shallow hidrology effect (ground water level change). From the gravity surveys in 2014 and 2016, there is big difference in long term drift between 2014 and 2016 data, which is 2014 has average value of 320 μGal/day and 2016 has average value of 120 μGal/day. Other than that, in repeatability test, 2014 has 54% and 2016 has 77% from total data that is within the range of deviation ± 10 μGal (repeatability value in accuracy of ideal Scintrex CG-5). Analysis of gravity data measured in three benchmark (BM) was also performed to know the gravity variation rate in research area.