**5. Closing remarks**

**Figure 15.** Repeatability of H result simulation baseline CNAB-CMAN 319,811.751 m.

98 Multi-purposeful Application of Geospatial Data

**Figure 16.** Repeatability of H result simulation baseline BNOA-CBTU 934,272.232 m.

**Figure 17.** Repeatability of H result simulation baseline BNOA-CDNP 100,619.250 m.

**Figure 18.** Example of real data of platform subsidence in platform X offshore of Indonesia.

Due to oil and gas exploitation, offshore oil and gas platform may experience subsidence. It has been observed from the real measurement that the rates can be varying from 1 to 10 centimeters per year and even more for certain places. In a detailed viewing, we can see fluctuation on the trend. Sometimes it is accelerating, while in some cases, it is slowing or linier. This situation will depend on how much oil and gas are being exploited and also how much pore pressure left, the fluid injection, etc. This subsidence information is mandatory for risk assessment and safety requirement. Continuing subsidence may deform the platform infrastructures, adding the risk for any failure on the platform objects. With surrounding full of gases and oil, the failure may cause fatality.

[2] Hofmann-Wellenhof B, Lichtenegger H, Walse E. GNSS Global Navigation Satellite

The Use of GNSS GPS Technology for Offshore Oil and Gas Platform Subsidence Monitoring

http://dx.doi.org/10.5772/intechopen.73565

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[3] Abidin HZ. Penentuan Posisi Dengan GPS dan Aplikasinya. 2nd ed. Jakarta: P.T. Pradnya

[5] Beutler G, Bock H, Brockmann E, Dach R, Fridez P, Gurtner W, Hugentobler U, Ineichen D, Johnson J, Meindl M, Mervant L, Rothacher M, Schaer S, Springer T, Weber R. Bernese

Systems: GPS, GLONASS, Galileo, and More. Wien: Springer Verlag; 2007

Paramita; 2000. 268 pp. ISBN: 979-408-377-1

[4] Leick A. GPS Satellite Surveying. 3rd ed. New York: Wiley; 2004

GPS Software Version 4.2. University of Berne; 2001. 515 pp

The capabilities of GNSS GPS technology on monitoring subsidence on oil and gas platform have been proven. By observing enough satellites, and measuring their distance, in this case the coordinate on location at the earth can be calculated precisely and even with precision in the order of millimeter. This technology can measure accurately an object as small as an ant. To get information of subsidence signal or any deformation signal, we just repeatedly or continuously monitor accurate positions on the objects investigation, and the changing of positions is representing subsidence and/or deformation.

For Indonesia case it can be interesting to discuss about the reference station for monitoring subsidence on the platform since Indonesia is an archipelago country. Most of the region is water, and many sources of oil and gas are taking place offshore. The scenario of choosing one reference station for whole Indonesia regions or by cluster can be used. Results from data simulation show that the scenario using reference station at clustered offshore are given better result than scenario using only one stable reference station. Nevertheless with using scenario of only one stable reference station, generally it is sufficient enough for monitoring offshore oil and gas platform subsidence in such large offshore like in Indonesia. For baseline with more than 1000 km when we get 1 cm of accuracy, it is very good indeed. It may give the effectiveness and efficiency to the monitoring projects by the oil and gas company and others.
