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体积压裂分支裂缝的产生条件分析
Analysis on the forming conditions of branching fractures in volume fracturing
李传亮 朱苏阳
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作者单位:西南石油大学石油与天然气工程学院
中文关键字:页岩油气 水平井 体积压裂 裂缝 破裂压力 应力差 数学模型
英文关键字:Shale oil and gas; Horizontal well; Volume fracturing; Fracture; Fracturing pressure; Stress difference; Mathematicl Model
中文摘要:    页岩油气藏的物性极差,需要水平井加体积压裂才能实现经济有效开发。水平井压裂产生主裂缝的破裂压力公式已经建立起来,但还没有建立分支裂缝的破裂压力公式。根据岩石力学的有关理论,以深层页岩地层为例,分析了主裂缝壁面上的受力情况,推导建立了垂直分支裂缝的破裂压力公式。公式表明:①分支裂缝的破裂压力与地层的最大水平地应力有关,与上覆压力和最小水平地应力无关;②分支裂缝的破裂压力比主裂缝的破裂压力高,二者的破裂压力差是由地层的水平应力差导致的;③水平应力差越大,破裂压力差就越大,地层就越不容易形成分支裂缝,也就越不容易实现缝网压裂,水平应力差小的地层,比较容易实现缝网压裂。结论认为:对于应力差大的地层,可以通过提高泵的功率和采用低黏压裂液来实现缝网压裂。
英文摘要:    For most shale oil and gas reservoirs, the physical properties are quite poor resulting that their economically effective development cannot be realized unless horizontal-well drilling + volume fracturing are adopted. So far, one formula for calculating the fracturing pressure of the main fractures induced by horizontal-well fracturing has been established, but that for branch fractures has not been set up yet. According to geomechanical theory, the stress on the wall of main fractures was analyzed by taking deep shale as an example. And then another formula to calculate the fracturing pressure of branch fractures was deduced. Results show that, (1) for branch fractures, the fracturing pressure is related to the maximum horizontal in-situ stress instead of the overburden pressure and the minimum one; (2) the fracturing pressure of branch fractures is higher than that of main fractures, and the difference between two fracturing pressures is caused by the horizontal stress difference in strata; and (3) the larger the horizontal stress difference is, the larger the fracturing pressure difference is, and the more difficult it is to form branch fractures and to implement network fracturing. And network fracturing can be carried out easily in some strata with smaller horizontal stress difference. In conclusion, the network fracturing in other strata with larger horizontal stress difference can be implemented by increasing pumping power and adding fracturing fluid with low viscosity.
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国内统一连续出版物号:CN51-1159/TE |国内发行代码: |国际标准出版物号:ISSN1673-3177 |国际发行代码:
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