煤岩T型缝压裂实验及压力曲线分析

Experiments of fracturing and pressure curve analysis of T-shape fractures of coal bed

煤层气的水力压裂会形成煤层内多裂缝共存的复杂裂缝系统,有利于提高煤层气产能,而压裂实验可以分析复杂裂缝系统的形成。采集山西保德区块原始煤岩制成规则形状的煤样,利用设计的三轴可变应力压裂实验设备对煤样进行了室内水力压裂模拟,实验时分别设定了煤样的三轴应力,实验后得到了煤层T型缝,分析了压裂压力曲线及压裂后的煤样。实验条件下生成T型缝的压裂压力出现了2个峰值,其后裂缝开始延伸。分析认为,当压裂受煤岩原生裂缝影响时,压裂曲线会出现多个峰值,且峰值之间差别较小。压裂曲线的特征有助于现场压裂时复杂裂缝的判断。

The hydraulic fracturing of coal bed methane can form complex fracture system and improve production.Fracturing experiment can analyze the formation of complex fracture system.A coal sample is acquired from the raw coal of Block Baode of Shanxi Province and then the sample is machined into a regular shape.The sample with hydraulic fracturing is simulated with the sample with the three-axis variable stress fracturing experiment equipment.Different tri-axial stresses are set while doing experiment.,get the result of the T-shape fractures are obtained after the experiment.The fracturing pressure curve and the coal sample after fracturing are analyzed.Under the experimental conditions,there exist two peaks in the fracturing pressure curve and after that the fractures extend.It is recognized that there appear multi-peaks and the difference between the peaks are small when raw coal sample is influenced by raw fractures.The characteristics of the curves is helpful for the judgment of complex fracture system in field fracturing implementation.