仿生学蒲公英支撑剂在类似煤层气裂缝网络中输运规律的物理模拟研究

Physical simulation study on the transport of biomimetics dandelion proppant in similar coalbed methane fracture network

  • 摘要: 加快深部煤层气资源勘探开发是煤层气的重点发展方向,但随着大规模体积压裂在深部煤层气开发中的应用,深部煤层压裂形成的裂缝复杂程度逐渐提升,但低黏度压裂液携带圆球形支撑剂在复杂深部煤层气裂缝中的输运性能和转向性能有限,导致圆球形颗粒对于分支裂缝及远端裂缝的铺置效果差,严重影响深部煤层气体积压裂的效果。在此基础上,基于仿生学的理念,提出了一种能在低黏压裂液中具备高效输运和转向能力的仿生学蒲公英支撑剂,为进一步了解不同施工参数情况下该种支撑剂在深部煤层裂缝中的输运和转向性能,基于深部煤层中常见的T 型裂缝,构建了T型可视化复杂裂缝支撑剂输运试验系统,研究了排量、射孔位置、压裂液黏度、支撑剂粒径、支撑剂浓度等施工参数对于仿生学蒲公英支撑剂在T型裂缝中输运及转向性能的影响,发现随着排量的提升,仿生学蒲公英支撑剂在T型裂缝主裂缝中的支撑面积和砂堤通道率逐渐提升,同时更多的支撑剂转向进入T型裂缝的分支裂缝中,说明排量增加,仿生学蒲公英支撑剂的输运和转向性能随之提升。仿生学蒲公英支撑剂在不同黏度的压裂液中均能保持较好的输运效率,同时能够堆积形成具有大通道的砂堤;中部单射孔能够在T型裂缝的分支裂缝和主缝中都形成更好的堆积效果;随着砂比的增加,支撑剂在T型裂缝的主裂缝和分支裂缝中的面积都逐渐增加,但增幅逐渐变缓,同时砂堤的通道率逐渐降低。基于施工因素的定性分析,综合推荐在深部煤层气应用仿生学蒲公英支撑剂时,采用中高排量、低黏度,中部射孔方式、小粒径支撑剂以及7%~11%砂比。本研究能促进仿生学蒲公英支撑剂在深部煤层压裂中的规模化应用,同时也对我国深部煤层气的高效开发具有重要意义。

     

    Abstract: Accelerating the exploration and development of deep coalbed methane resources is a key direction for developing coalbed methane. However, with large-scale volume fracturing in deep coalbed methane development, the complexity of the fractures formed by deep coalbed methane fracturing gradually increases. However, the low-viscosity fracturing fluid carrying spherical proppants has limited transport and turning performance in complex deep coalbed methane fractures, resulting in the poor placement of proppant on the branch and deep fractures, seriously affecting the effect of deep coalbed methane large-scale volume fracturing. Thus, the author proposes a biomimetic dandelion proppant with efficient transport and steering capabilities in low-viscosity fracturing fluids. To further understand this proppant's transport and steering performance in deep coal seam fractures under different construction parameters, this study constructs a T-shaped visualized complex fracture proppant transport experimental system based on common T-shaped fractures in deep coal seams. The effects of construction parameters such as pump rate, perforation position, fracturing fluid viscosity, proppant particle size, and proppant concentration on biomimetic dandelion proppant transport and steering performance in T-shaped fractures were studied. It was found that with the increase of pump rate, the support area of biomimetic dandelion proppant in the primary fracture of T-shaped fractures would increase. The sand embankment channel rate was gradually increasing. At the same time, more proppants were turning into the branch fractures of the T-shaped fractures, indicating an increase in pump rate and an improvement in the transport and turning performance of the biomimetic dandelion proppants. Biomimetic dandelion proppants could maintain good transport efficiency in fracturing fluids of different viscosities and accumulate to form sand embankments with large channels. A single perforation in the middle could form better accumulation effects in both the branch and central fractures of the T-shaped fracture. As the sand ratio increases, the area of the proppant in the primary and branch fractures of the T-shaped gradually increases. However, as time passes, the increase of proppant area would slow down, and the channel rate of the sand embankment gradually decreases. Based on qualitative analysis of construction factors, it is recommended to use biomimetic dandelion proppant with medium to high displacement, low viscosity, middle perforation method, small particle size proppant, and 7%–11% sand ratio when applying it to deep coalbed methane. This study can promote the large-scale application of biomimetic dandelion proppants in deep coal seam fracturing and is also of great significance for the efficient development of deep coalbed methane in China.

     

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