川东石炭系气藏天然气富集的三元控制理论

the THEORY of THREE FACTS CONTROLLING GAS FOR CARBONIFEROUS RESERVOIR GAS ENRICHING IN EASTERN SICHUAN

川东石炭系是川东地区碳酸盐岩地层中最重要的一套含气储集层,天然气储量很大部分蕴含于特征的地层-构造复合圈闭之中,天然气在地层-构造圈闭中的富集主要受3个因素控制,即由石炭系地层厚度控制的地层元,由主体背斜、潜伏构造控制的构造元和由内部针孔及溶孔白云岩(有效储层)控制的储层元。石炭系残厚大于10米的区域就是地层-构造圈闭的理论含气范围,而石炭系残厚大于50米的区域是天然气形成工业性聚集的范围;在地层-构造圈闭之内,构造元和储层元控制着天然气富集的实际范围,那些埋藏适中、且无通天断层破坏的主体构造和潜伏构造是最有利的含气区域;而在非构造控制区域内,储层元起控制作用,中上段的溶孔及针孔白云岩(有效储层)累计厚度大于25米,或者其累计厚度占石炭系残厚在一半以上,符合此两条件之一的区域即为富气的有利区域。三元控气理论可以指导川东地区天然气的勘探实践。

carboniferous system is one of the most important gas bearing reservoir among the carbonate formation in the east Sichuan area.Lots of gas reserves contain in the characteristic stratigraphic-structural combination trap.three facts control the gas enrichment within the trap.They are stratagraphic fact controlled by the bed thickness,and the structural fact controlled by the main body structure and buried structure,as well as the reservoir fact controlled by the pin hole and the corroded hollow dolomite rock.The region whose carboniferous residuum thickness is more than 10 meters is the theoretical gas zone.While the region whose carboniferous residuum thickness is more than 50 meters is range which can form the productive gas accumulation.Within the range,structural and reservoir fact control the actual region enriching gas.The main body which has suitable buried deepness and has no destroying fault and the buried structure are favorable gas zone.Within the non structural controlling zone,the reservoir fact play the main role in controlling the enriching gas.The accumulating deepness of the the pin hole and the corroded hollow dolomite rock(effective reservoir) is more than 25 meters.Or it is more than half of the carboniferous residuum deepness,the region meeting either of two conditions is favorable gas zone.The theory of three fact controlling gas can guide the gas exploration practice in eastern Sichuan.