贵州五轮山井田构造演化与煤层气成藏

Tectonic Evolution and CBM Reservoir Formation in Wulunshan Minefield, Guizhou

贵州五轮山井田自二叠系煤层形成以来,主要经历了三期构造应力场的更替。在构造控制下,煤层主要经历了四期煤化作用。煤层气主要生产阶段,发生在印支期末—燕山早期,保存的煤层气资源量巨大,据勘探资料推算,可采煤层的煤层气含量达到7.14～32.30m3/t.r。构造演化研究表明,自燕山期煤层气成藏以来,五轮山地区处于持续抬升剥蚀状态,煤层埋藏不断变浅,并发育了多组节理和断层。该区构造较为完整,煤层厚度较大,其主力煤储层层间距较小,盖层以泥岩为主,虽经多期构造改造,盖层仍保存完整,煤层较小,为煤层气的创造了条件。

The Wulunshan minefield, Guizhou had experienced 3 stages of tectonic stress field replacement. Under the tectonic control, coal seams experienced 4 stages of eoalification. The main CBM producing stage was during the late Indo-China to early Yanshanian stages and/ibundant CBM resources preserved. Estimation from exploration data, CBM content in mineable coal seams can be 7.14~32.30m3/t ·r. The tectonic evolution study demonstrated that since the formation of CBM reservoir during Yanshanian stage, the Wulunshan area was stood in continuous uplifting and denuding state, coal seam buried depth was constantly shallowed, many sets of joint and fault have developed. Structures in the area are rather integrated whole, coal seam thickness is rather large, intervals between coal reservoirs rather small, capping bed is mainly mudstone. Although experienced multi staged tectonic reformation, capping beds are still completely preserved, thus a favorable condition to CBM preservation.