临兴深部煤层气含气性及开发地质模式分析

鄂尔多斯盆地东缘晋西挠褶带临兴中部地区煤层埋深大于1 000 m,达到了深部煤层气的研究范畴。基于实际生产资料,探讨区内深部煤层含气性,提炼了深煤层开发地质模式。研究认为:以含气量转折为深煤层临界深度的划分依据,则工区内深部煤层的临界深度在2 000 m左右;且深部中煤阶储层的吸附性对温度的敏感性要小于压力,中煤阶煤层的临界深度相对深于高煤阶;深部煤层气仍以吸附气为主,现有的等温吸附测试方法易造成深部煤层气含游离气比例换算较大的误区;深部煤层受温度影响,煤层临储比较高,受应力影响,储层物性较差,气井总体具有"见气快、排水降压难、产气量上升缓慢"的特点;研究区深部煤层气潜力巨大,现有气井经验显示,合理优化开发单元为深煤层单井突破的关键,A型"源-储"相通的富集开发地质模式是深煤层突破重点考虑的开发模式。

Gas analysis of deep coalbed methane and its geological model for development in Linxing Block

Depth of coal seams in Linxing middle area of the east margin of Ordos is more than 1 000 m,which has reached the research field of deep CBM.Based on the actual production data,this paper discusses the gas bearing capacity of deep coal seam,and refines the development geological model of deep coal seam in the area.The study shows that critical depth of the deep coal seam divided by the turning of gas content is about 2 000 m in the work area.Adsorption sensitivity of deep middle coal rank reservoirs is less sensitive to temperature than the pressure,so that critical depth of medium rank coal seams is relatively deeper than that of high rank coal seams.Deep coalbed gas is still mainly adsorbed gas,and the existing isothermal adsorption testing method is easy to cause the misunderstanding of the proportion of free gas in deep coalbed methane.Due to the influence of temperature,the deep coal seam is relatively high in temporary storage ratio.Due to the influence of stress,the reservoir properties are poor.The gas wells generally have the characteristics of “quick gas seepage,difficult drainage pressure reduction and slow gas production increase”.The potential of deep coalbed methane is huge.The experience of gas well shows that rational and optimized development unit is the key to the single-well breakthrough in deep coal seams.The enriched development geological model associated with Type A “source-reservoir” is a development model that is mainly considered in the breakthrough of deep seams.