基于黏聚层单元的缝内暂堵压力演化规律的有限元数值研究
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TE357

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国家自然科学(No. 51804033、No. 51936001和No. 51904031)、北京市高水平创新团队建设计划项目(No. IDHT20170507)、长城学者培养计划(No.CIT TCD20180313)、北京市重点联合(No. KZ201810017023)和北京市拔尖人才计划项目(No. CIT TCD201804037)联合支持。


Numerical Study on the Evolution Law of Temporary Plugging Pressure in the Hydro-fracture via Cohesive Zone Method Based Finite Element Analysis
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    摘要:

    暂堵转向压裂技术是目前高效改造低渗透难动用油气藏的“杀手锏”技术,目前缺乏对缝内暂堵压力演化规律方面的研究。本文基于粘聚层单元理论模拟暂堵带,采用应力-渗流全耦合有限元模型,对暂堵转向压裂过程中暂堵带封堵长度、暂堵剂封堵强度、压裂液注入排量、暂堵带滤失系数等因素对缝内压力变化的影响规律进行了数值模拟研究,并通过灰色关联分析确定各因素对缝内压力影响能力的相对关系。结果表明:暂堵剂封堵长度达到5m后,暂堵带的承压能力将趋于稳定;随暂堵剂封堵强度的增大,增压幅度呈现先快速上升后逐渐放缓的趋势,缝内压力可提升超过15%,有助于缝内形成憋压;增大压裂液注入排量可缩短76.3%的升压时间,有效加快缝内压力提升速率;暂堵带滤失系数减小至某一小值后,缝内增压效果明显且趋于稳定;根据关联系数分析得出影响能力从大到小的排序为:排量>暂堵剂封堵长度>暂堵剂封堵强度>渗透系数。本论文的研究成果对指导缝内暂堵转向压裂设计具有重要意义。

    Abstract:

    Temporary plugging and diverting fracturing technology is the “trump card” technology for the efficiently stimulate the low-permeability reservoirs that are hard to develop. However, at present, there is lack of study on the evolution law of temporary plugging pressure in the hydro-fracture. In this paper, temporary plugging zone is numerically simulated according to the theory of cohesive zone method (CZM) through a fully coupled stress-seepage finite element model. The main influence factors of the pressure change in the fracture, such as the length of the temporary plugging zone, plugging strength of temporary plugging agent, the injection rate of fracturing fluid, leak-off coefficient of temporary plugging zone is considered in this FEM model. The order of these factors which affect the temporary plugging pressure in the hydro-fracture is determined by the gray relation analysis. The results show that: (1) after the plugging length of the divert agent is up to 5 m, the bearing capacity of the temporary plugging zone will tend to be stable; (2) with the increase of the blocking strength of the temporary plugging agent, the scale of fluid pressure variation will rise rapidly at early stage and then slow down gradually; (3) Increasing the injection rate of fracturing fluid is beneficial to shorten the time of pressure increase by 76.3%, which can effectively improve the capacity of temporary plugging in the hydro-fracture. After the leak-off coefficient of temporary plugging zone decreases to a small value, the pressurization effect is obvious and tends to be stable. According to the gray relation analysis, the order of influence factors of temporary plugging pressure is as follows: injection rate > the length of the temporary plugging agent> plugging strength of temporary plugging agent > leak-off coefficient. The results in this paper have important instruction significance to design the scheme of temporary plugging and diverting fracturing.

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秦浩,汪道兵,李敬法,等. 基于黏聚层单元的缝内暂堵压力演化规律的有限元数值研究[J]. 科学技术与工程, 2021, 21(10): 4011-4019.
Qin hao, Wang Daobing, Li Jingfa, et al. Numerical Study on the Evolution Law of Temporary Plugging Pressure in the Hydro-fracture via Cohesive Zone Method Based Finite Element Analysis[J]. Science Technology and Engineering,2021,21(10):4011-4019.

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  • 收稿日期:2020-06-10
  • 最后修改日期:2021-04-04
  • 录用日期:2020-10-24
  • 在线发布日期: 2021-04-28
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