TS区块煤层压力预测研究

Prediction of Coal Seam Pressure in TS Block

相较于普通的储层而言,煤岩极为特殊,不仅存在割理发育现象,而且强度相对较低,当进行钻井时,将会频繁出现井壁坍塌事故。除此之外,煤岩本身的结构,并不有利于煤井井壁含有的稳定性,因此,研究煤层的三压力剖面。根据井壁周围的围岩应力以及井壁应力分布特征确定修正系数,通过实验确定煤层岩石力学参数,建立地层孔隙压力,坍塌压力,破裂压力模型确定三压力剖面。研究结果表明,孔隙压力和坍塌压力正常,破裂压力因不同层系波动较大,因此,在钻井过程应该适当控制钻井液密度,避免压破地层。

Compared with conventional reservoirs, coal reservoirs are characterized by low strength and well cleavage structure, and borehole wall instability is serious during drilling. At the same time, the particularity of coal and rock structure also increases the difficulty of studying the mechanism of borehole wall instability of CBM wells. Therefore, the study of three pressure profiles of coal seams is necessary. According to the surrounding rock stress around the wellbore and the distribution characteristics of the wellbore stress, the correction coefficient is determined. The rock mechanics parameters of coal seam are determined by experiments. The pore pressure, collapse pressure and fracture pressure models are established to determine the three pressure profiles.The results show that the pore pressure and collapse pressure are normal, and the fracture pressure fluctuates greatly due to different formations. Therefore, the density of drilling fluid should be properly controlled in the drilling process to avoid fracturing formation.