中国致密砂岩气及在勘探开发上的重要意义

Tight gas in China and its significance in exploration and exploitation

致密砂岩气藏系指聚集工业天然气的致密砂岩场晕或圈闭,根据其储集层特征、储量大小及所处区域构造位置高低,可将致密砂岩气藏分为两类:"连续型"致密砂岩气藏和"圈闭型"致密砂岩气藏,前者通常位于构造低部位,圈闭界限模糊,无统一气水界面,往往气水倒置,储源一体或近源;后者位于圈闭高处,上气下水,储量规模较小但产量相对较高。中国致密砂岩气都是煤成气,组分以烷烃气(C1 4)为主,甲烷含量最高,烷烃气具正碳同位素系列;非烃气(主要是CO2和N2)含量低。截至2010年底,中国致密砂岩气的储量和年产量分别占全国天然气储量和产量的39.2%和24.6%,预计将来比例还会提高。与页岩气、煤层气等非常规气相比,中国近期在非常规气勘探开发中应以致密砂岩气为先。

Tight gas reservoirs refer to the tight sandstone fields or traps accumulating natural gas of commercial values.According to reservoir characteristics,reserves,and structural height,they can be divided into two types,continuous-type and trap-type： the former are located at the lower part of the structure and have indistinct trap boundaries,inconsistent gas-water boundaries and reversal of gas and water,and their reservoirs are the same as or near the source;the latter are located at the higher part of the structure,with gas above water in traps,low reserves,and relatively high production.Tight gas in China is all coal-derived,dominantly alkane gases（C1—4）,in which the amount of methane is greatest and the alkane gases have positive carbon isotopic series.The content of non-hydrocarbon gases（mainly CO2and N2） is low.At the end of 2010,the reserves and annual production of tight gas in China accounted for 39.2% and 24.6% of the total natural gas,respectively,and the proportions are expected to increase.Compared to the shale gas and coalbed gas,tight gas should be considered in priority in the exploration and exploitation of unconventional gas in China.