中国煤层气勘探的新思路

NEW THEORY FOR COALBED GAS EXPLORATION IN CHINA

我国的煤层气资源量约为３５×１０１２ｍ３。近年来，已在２０多个含煤区进行了煤层气勘探，４层气探井数已达７０口，其中煤层气日产逾千立方米的井仅有６口。目前的勘探特点为：①产量低，递减快；③煤层渗透率低，压力低；③煤阶低；④煤层埋藏浅，处于甲烷风化带；⑤煤层薄，顶底板砂岩含水层发育；③有的煤层埋藏太深。拟合于固体勘探和流体勘探之间的煤层气勘探，其最大特点是气源岩与储气层同层，勘探开发的重点是煤层中的吸附气，研究的重点是搞清控制煤层中甲烷的分布、储存能力和气井产能的地质及水文因素。必须突破旧有思路的束缚，从煤层气勘探的选区评价、布井、钻井、完井和增产措施到开采方式、集输和环境保护等方面建立起一整套行之有效的工作程序和勘探方法。勘探重点地区应为华北地区的京津唐含煤区以及山西、陕西和河南的部分含煤区等；其次是华南地区的有利含煤区。

In recent years, coalbed gas exploration has been done in 20 coalbed areas in our country, the number of exploration wells has reached 70,but there are only 6 wells whose production is above 1 000 m3/d.The characteristics of the present exploration are:①low production, rapid decrease;②low permeability and pressure;③low coal step; ④the hurlal depth of coalbed is shallow and locate at the weathered zone of methane; ⑤the coalbed is thin,the aquifer at the top and bottom of sandstone is well developed, and the burial depth of some coalbed is very deep.Coalbed gas exploration lies between coal exploration and oil-gas exploration, it's outstanding characteristic, is that the gas source rock and gas-bearing reservoir are at the same layer, and the focal point of exploration is the absorbed gas in coalbed. To make clear the geology and hydrology factors that control the methane distribution in coalbed, storage capability and gas well productivity, it's necessary to break through the limitation of old theory, in addition, build a set of working procedure and exploration method of evaluation,well spacing, well drilling,well completion, stimulation, recovery method,gathering and environmental protection.The coalbed resource in our country is about 35 trillion cubic meters and 'lainly distribute in Jingjintang area of North China, Shanxi,Shanxi, Henan and South China.