鄂尔多斯盆地合阳地区煤层气赋存特征研究

Study on occurrence features of coalbed methane in Heyang area, Ordos Basin

鄂尔多斯盆地合阳地区是我国煤层气勘探的重要区块,在该区进行煤层气赋存特征研究并预测煤层气资源量,对其进一步的开发十分必要。为此,从地质条件、储层特征(煤层分布、煤层埋藏深度、煤岩特征、煤储层吸附性、煤储层压力、煤储层渗透性及煤层含气性)等方面入手,分析了该区煤层气的赋存特征。结果表明:该区煤层气的保存条件优越;主要含煤地层为二叠系山西组和太原组,含煤层11层,可采或局部可采煤层4层,煤层累计厚度为11 m左右,主力煤层为5号煤层,单层厚度超过3 m;煤质以中—高灰分、低挥发分的贫煤为主,受构造活动破坏的影响较小,煤岩的原生结构较完整,煤储层含气量高且吸附性强。煤层气资源量预测结果表明:该区煤层气主要分布在埋深小于1 600 m的范围内,煤层气资源量约为442.72亿m3,其中埋藏深度小于1 300 m的煤层气资源量约为335.01亿m3。由此可见,合阳地区煤层气具有很好的勘探开发前景。

Heyang area in Ordos Basin is an important block of coalbed methane exploration in our country, so to study the occurrence features of coalbed methane and predict coalbed methane resources is necessary for field development. This paper analyzed the occurrence of coalbed methane in this area in respect of coalbed methane reservoir characteristics including burial depth and thickness of coal layer, features of coal, adsorption and pressure of coal reservoirs, permeability of coal reservoirs, as well as gas content. The results show that the preservation conditions of coalbed methane are advantage. The main coal-bearing strata are Shanxi Formation and Taiyuan Formation of the Permian, containing 11 layers coal, of which 4 layers are recoverable or partially recoverable, the cumulative thickness of coal seam is about 11 m, and the main coal seam is NO.5, of which the thickness is more than 3 m. The coals are dominated by lean coal with high ash and low volatile. Less affected by the destruction of tectonic activity, the original structure of coal is more complete, and the gas content of coal reservoir is high and the adsorption is strong. The prediction result of coalbed methane resources in this area shows that coalbed methane mainly occurs in coal layers shallower than 1 600 m with a cumulative coalbed methane resource volume of 442.72 ×108m3. Among them the coalbed methane resource volume with buried depth shallower than 1 300 m is 335.01×108m3.Therefore, the coalbed methane in Heyang area has very good prospects for exploration and development.