煤层应力敏感性及其对压裂液滤失的影响Experimental study on the stress sensitivity of coal and its impact on the filtration of the fracturing fluid
冯利娟,郭大立,曾晓慧,朱卫平,刘川庆
FENG Lijuan1,GUO Dali2,ZENG Xiaohui3,ZHU Weiping1,LIU Chuanqing1(1.Graduate School
摘要(Abstract):
压裂液滤失系数是压裂设计中非常重要的参数。由于煤层中的渗透率、孔隙度等物性对应力极为敏感,在对煤层进行压裂设计时,若直接用试井和测井测得的渗透率和孔隙度值代入滤失系数的计算公式,算出的结果可能与实际情况严重不符。通过实验室内不断改变围压的方式来模拟煤储层上覆压力的变化情况,建立了某盆地煤层应力与渗透率之间的关系,并在考虑煤层物性应力敏感性的情况下,探讨了煤层压裂液综合滤失系数的计算方法。结果发现,压裂液综合滤失系数及岩心渗透率与净围压的关系均符合指数递减规律。另外,通过对动态渗透率的拟合,使得到的综合滤失系数远远大于未考虑应力情况下的综合滤失系数,这样能更准确地反映实际情况。
The filtration coefficient of fracturing fluid is an important parameter in fracturing design.If the per-meability and porosity values obtained from well testing and logging are directly substituted into the equation of calculating filtration coefficient,the results calculated may be entirely different from the practical case,because the petrophysical parameters such as permeability and porosity,etc.are very sensitive to the stress in coal bed.Coal bed reservoir,fractured reservoir and tight sand reservoir are typical sensitive reservoirs.So it is necessary to study the stress sensitivity in coal bed.In the article the relationship between the stress and permeability in the coal res-ervoir was set up by simulating the coal reservoir pressure suffered by the overlying formation.And the method of calculating overall filtration coefficient during fracturing in coal bed is also generally discussed.The results show that both the overall filtration coefficient and permeability accord with the exponential decline law.Besides,on the basis of fitting of the dynamic permeability,the overall filtration coefficient under the consideration of stress sen-sitivity is higher than that which doesn’t consider the stress sensitivity,which is more practical and can describe the actual situation.
关键词(KeyWords):
煤层;压裂液;滤失系数;应力敏感性
coal bed;fracturing fluid;overall filtration coefficient;stress sensitivity
基金项目(Foundation):
作者(Author):
冯利娟,郭大立,曾晓慧,朱卫平,刘川庆
FENG Lijuan1,GUO Dali2,ZENG Xiaohui3,ZHU Weiping1,LIU Chuanqing1(1.Graduate School
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