Geophysical Responses And Distribution Of Carboniferous Volcanic Rocks In Ludong Region Of Juggar Basin

Based on the main Carboniferous distribution area in Ludong region of Junggar Basin which distributes some density of two-dimensional seismic lines, this paper studied the geophysical responses and their distribution of Carboniferous volcanic rocks. Though studying the three-dimensional seismic project of Dixi 10 well in Dinan bulge, combining the methods of marking seismogeological horizon, the relationship between each lithologic member of wells and seismic response nearby wells of Carboniferous System can be created. And through using the two-dimensional seismic lines of well tie regional framework, combining methods of division and matching of successions among outcrops, well drilling and seismic, and methods of recognition and correlation of seismic of sequence boundary marks, this paper also builds the Carboniferous seismogeological sequence framework and seismogiological interpretation scheme with uniting the wells and seismic data of internal basin.Mainly using the method of combining the wells and seismic data, this paper studied and analyzed the logs of important wells and their characteristics on the seismic profiles. According to the major seismic facies characteristics of Carboniferous volcanic rock, the results display:(1)Lithologies in the upper volcanic rocks member change frequently, and they also have stronger reflected wave in the seismic profiles.(2)Lithologies in the lower volcanic rocks member is relative stability.Thereby the curves of lower volcanic rock member manly keep stable, and mostly display weaker amplitude and chaotic seismic reflection with local stronger amplitude and more continuous reflection which indicate the energy of internal reflected wave is weaker.(3)Sedimentary rock member can usually find continuous and stronger amplitude reflection events in the seismic profiles, which mostly display continuous and subparallel reflection characteristics.Based on lithology,(1)The effusive facies of basalt and andesite can display some features such as stronger amplitude, more continuous reflection, low frequency, layered parallel reflection and so forth. Basalt and andesite usually appear in upper volcanic rock member of Carboniferous which have complicate and quickly changing lithologies characteristics and easily formed clear seismic reflection.(2)The explosive facies of tuff also display some features like strong amplitude, worse continuity, lower frequency, sub-layered reflection and so forth.(3)The effusive facies of rhyolite display their features like strong amplitude, well continuity and layered reflection. This is because rhyolite generally appears in lower volcanic rock member, and has individual lithology. Hence, its seismic facies has worse obvious features and worse layered than basalt and andesite.(4)The transition facies of interbedded sand and mudstone have their features including strong amplitude, well continuity and layered parallel reflection, low frequency and so forth.From the aspect of the volcanic phase to analyze: (1)Volcano channels phase appearance is nearly vertical irregular pillars、mushroom form、strong amplitude、low frequency、blank, mixed and disorderly Concentres reflection.(2)Volcano outbreak phase appearance is waveform,earthworm shape, lay-like structures , strong amplitude, concentres reflex, disorderly, extensions closer.(3)Volcano relief phase appearance is dome shape, wedge, broom shape, strong amplitude, low frequency, continuous reflex, extensions is long.In tne aspect of area distributing,(1)Upper volcanic rock member usually is absence,and represent square shape,only exist in the low-lying of hollow of basin(2)The sedimentary rock which between the upper and lower volcanic rock widely exist in the ludong area,just run short of in the heave area.(3)Lower volcanic rock is mostly abroad in the area.There is a lack of lower volcanic rock in the north of the heave of the dibei area,in the south of the heave of dinan area,and in the north of wucaiwan hollow,but the scarcity range is obvious small when compare with the scarcity part of sedimentary rock.