准噶尔盆地陆东—五彩湾地区石炭系火山岩电性与地震响应特征

勘探实践证实,准噶尔盆地石炭系已成为一套现实勘探层系;陆东－五彩湾地区石炭系火山岩体规模大、分布广,是重要的天然气储集体;火山岩储层有效性主要受不整合、岩性、岩相控制,识别火山结构、火山岩岩性、岩相成为判别储层有效性的关键.由于主要目的层巴塔玛依内山组特殊的三段式火山岩组合层序结构,为通过测井、地震物探手段识别火山岩岩性、岩相创造了条件.基性熔岩具高密度、高电阻率、高自然伽玛电性特征,中基性熔岩具高电阻率、高密度、低自然伽玛电性特征,中酸性熔岩具中电阻率、中等密度、较高自然伽玛电性特征,火山角砾岩相具低电阻率、中低密度、高自然伽玛电性特征,凝灰岩具低电阻率、低密度、高自然伽玛电性特征.上、下火山岩段表现为不连续的丘状反射或杂乱反射;中部沉积岩段表现为较强振幅、较连续的平行与亚平行结构反射;依据波组反射结构特征,能够识别出层状火山、锥状火山、浅成侵入体三类火山岩结构.火山岩储层均属风化壳型储层;储层有效性受岩性与岩相控制.近口亚相带主要发育于滴南凸起带、滴北凸起带、石西—石南凸起带、五彩湾凹陷南北缘、白家海北缘;远火山口亚相多发育于火山后亚相的东西两侧;溢流相带主要沿主断裂由南向北展布.近源的构造、岩性、岩相匹配的风化壳储层发育区,最有利于成藏;形成构造背景下的地层-岩性型原生火山岩天然气藏.

The electric characteristics and seismic response of Carboniferous volcanic rock in Ludong-Wucaiwan area of Junngar basin

It has been proved by practice of exploration that the Carboniferous System in the Junggar Basin is a set of prospective strata of actual exploring. The carboniferous volcanic rock has a large scale and a wide distribution in the Ludong-Wucaiwan area, and is an important reservoir rock of gas. The availability of volcanic reservoir rock is mainly influenced by unconformity, lithology and lithofacies control. Hence, the key to judge the availability of reservoir are to identify volcanic architecture, volcanic rock lithology and lithofacies. The major bed of interest called Batamayineishan Formation has a special triple architecture of volcanic rock sequence, which facilitates the identification of volcanic rock lithology and lithofacies through logging and seismic geophysical prospecting. Basic lavas have the features of high density, high resistivity and high electrical properties of natural gamma. Intermediate basic lavas are similar to basic lavas, but they have low electrical properties of natural gamma. On the contrary, volcanic breccia facies have a low resistivity and medium to low density, but have high electrical properties of natural gamma. Similarly, tuff, whose density is lower, also have the features like volcanic breccia. In addition, intermediate acid lavas have the features between the two extremes, with slightly high electrical properties of natural gamma. The upper segment and the lower segment which are volcanic rocks show the discontinuous mounded reflection or chaotic refection, but the middle segment which is sedimentary rock displays stronger amplitude and more continuous parallel and sub-parallel reflection. According to the characters of composite wave reflection configuration, it is possible to identify three volcanic rock architectures which are layered volcano, konide and hypabyssal intrusive, respectively. Volcanic rock reservoirs all belong to the type of weathering crust reservoirs and the reservoir availabilities are controlled by lithology and lithofacies. The sub-facies nearby the volcanic vents mainly develop in the Dinan bulge zone, Dibei bulge zone, Shixi-Shinan bulge zone, the south and north margins of Wucaiwan Sag and the north of Baijiahai. Most of the sub-facies which are far away from volcanic vents develop on the east and west sides of sub-facies after the volcano explode. Effluence facies mainly distribute in South-North major faults. The weathering crust reservoirs which are coupled with nearby structures, lithology and lithofacies, are the best to form the oil/gas reservoir, which form the stratigraphy-lithology origin volcanic rock gas reservoirs in the tectonic settings.