Seismic chimney

The identified characteristics of secondary hydrocarbon migration can be verified with e.g. the location and physico-chemical characteristics of known hydrocarbon accumulations (e.g. England and Mackenzie, 1989) direct and indirect observations of oil and gas seeps (direct visual observations indirect observations, such as hydrocarbon-charged sediments, pock marks, clay diapirs) and gas leakages indicated by seismic chimneys. 

Towers and chimneys are among the most vulnerable structures in seismic excitation because of their slenderness. They can be tested according to Eurocode 8, part 3 Towers, masts and chimneys (2003). Support stays are often used to reinforce them against earthquake effects. 

A detailed account of the seismic activity in the state of Washington will be included in Appendix I of Volume II. Briefly, tremors recorded at Hanford since 19 9 have apparently approached an intensity of six on the Modified Mercalli Scale of 1931 is corresponds to a ground "acceleration of about 0 05 g and is sufficient to cause the "falling of plaster and chimneys, (with) damage small as is shown in Table h- 3 ... 

Passive compensator systems are used as earthquake prevention installations with satisfactory success. Like any other anti-earthquake strategy, their efiiciency is limited by the way they are adapted to the loading history of the expected seismic events. On the other hand, they are useful for many other anti-oscillation applications such as bridges under traffic load or chimneys under wind exposure. 

Fig. 4. [Reproduced in colour in Plate 5 on page 423.] An example of a seismic cube with a chaotic pattern representing a gas chimney is shown in (a), its dip and Eizimuth attributes in (b) and (c) and a chaos texture attribute highlighting the gas migration path in (d).

In the 2D case, a cross-section from an azimuth attribute cube [16] can be used as input data. An attribute is defined as a mathematical operator, or a composition of operators, capturing properties from seismic data. The azimuth attribute has, together with other attributes, such as dip, chaotic texture and continuity, been successfully applied to mapping carbonate reef structures, gas chimneys, channels, fans, faults etc. 

In our approach, the 3D nature of the seismic data is preserved. The analysis is made using a neural network algorithm producing a 3D classification output. The value of this approach to 3D seismic texture mapping has already been demonstrated in the analysis of gas chimneys [25, 34]. Distinct advantages of the approach are that (1) it is independent from and requires no previous horizon interpretation, (2) multiple attributes are simultaneously... 

P. Meldahl, R. Heggland, B. Bril, and P. de Groot (1999) The chimney cube, an example of semi-automated detection of seismic objects by directive attributes and neural networks part 1 methodology. In Expanded Abstr., 69th Arm. Int. Mtg., Soc. Expl. Geophys., Houston, USA, 1999. 

---