低煤阶应力敏感性机理及其对产气的影响——以二连盆地为例

为研究低煤阶应力敏感性机理,建立双重孔隙介质应力敏感性模型和产气预测模型,基于应力敏感性实验和数值模拟,讨论了应力敏感性对高、低煤阶的产气影响。研究表明:应力敏感性与煤岩微观结构、力学参数、压缩性质有关,弹性模量越小、裂缝压缩系数越大,应力敏感性越强;含裂缝煤岩应力敏感性强于无裂缝煤岩,多次升降压会造成渗透率的不可逆降低;非连续排水会产生地层压力波动,产气量比连续排水时要低,而且应力敏感性越强,非连续排水对产气影响越大;应力敏感性对霍林河地区产气影响大于樊庄地区,针对巨厚煤层、强应力敏感性的特点,可试验直井"分段间接"压裂、顶板"L"型水平井分段压裂以降低应力敏感性、改善渗透性,提高单井产量。

Stress sensitivity mechanism of low-rank coal and its influence on gas production：A case study from Erlian Basin

In order to study the stress sensitivity mechanism of low-rank coal,the dual media stress sensitivity model and gas production forecast model were established.Based on the stress sensitivity experiment and numerical simulation,the influence of stress sensitivity on the gas production of high and low rank coal were discussed.This research show that：The stress sensitivity is related to the microstructure,mechanical parameters and compression property.The smaller the elastic modulus and the greater the fracture compressibility coefficient,the greater the stress sensitivity.The stress sensitivity of coal with fracture is greater than that of coal without fracture.Multiple increase and decrease of pressure would irreversibly reduce permeability.Discontinuous drainage would cause pressure fluctuation.The gas production is lower than that when the drainage is continuous,the greater the stress sensitive,the greater effect on gas production.The effect of stress sensitive on gas production in Huolinhe area is greater than that in Fan Zhuang area.Due to the characteristic of thick coal and strong stress sensitive,the multistaged indirect fracturing technique and staged fracturing in type “L” horizontal well in roof could be applied to reduce stress sensitivity and improve permeability and gas production.