寿阳区块煤层气井排采影响因素分析

Analysis of Influence Factors of CBM Wells in Shouyang Block

通过对寿阳区块煤储层地质条件、煤层气井钻完井工艺参数及排采控制特征的分析,认为影响该区块煤层气排采的主要因素有:生产煤层渗透率低、临界解吸压力低、含气饱和度低;本区块主力煤层15号煤的顶板以灰岩为主,含有不规则的裂隙水,导致部分井产水异常;构造复杂易造成直井压裂裂缝或水平井水平段与断层发生沟通,导致煤层与外部水层发生连通而干扰煤层的排水降压;水平井钻井过程中使用的泥浆体系对煤储层造成一定伤害,部分直井压裂后未及时返排并长时间未投入排采,压裂液长期浸泡煤层;因各种原因造成频繁的排采中断。针对这些主要影响因素,提出了针对性建议。

Through the analysis of the geological condition of coal reservoirs in Shouyang Block,the parameters of CBM well drilling and completion processes and characteristics of recovery control,the paper proposes that that the main factors influencing the CBM recovery in the Block includes the low permeability of the main coal seam,the low critical desorption pressure and low gas saturation. The roof of 15 # coal seam,which is the main seam in the Block,is mainly limestone,with irregular fissure water,which causes the abnormal water production in parts of wells. The complex structure also causes the fracturing cracks in the vertical wells or the communication of the horizontal section with the fault in the horizontal wells,and leads to the connection between the outer water layer and coal seam,and interfere the water drainage and pressure release of the coal seam. The mud system used in the process of horizontal well drilling will bring certain damage to the coal reservoir. Some of the vertical wells could not be flow back timely and put into operation for long time after fracturing,which causes the long-term immersion of the fracturing fluid to the coal seam. There are also various reasons causing the frequent interruption of gas recovery. According to these main influence factors,the paper puts forward the countermeasures.