摘要
支撑剂嵌入裂缝壁面会降低人工裂缝的导流能力,加快产能递减,使前期的压裂增产施工效率降低,甚至无效化。因此,在生产实践中,多采用多层铺置的模式增加裂缝导流能力,降低支撑剂嵌入及变形的负面影响。但是,现有支撑剂嵌入模型大多建立在支撑剂正方形排列单层铺置的基础上,模型太过理想化,对嵌入后导流能力的模拟并不准确。为使模型计算结果更接近实际,充分考虑支撑剂菱形排列多层铺置对压后支撑缝宽的影响,基于弹性力学和Hertz接触理论对支撑剂在原地应力作用下的应变进行分析,建立了压后支撑缝宽变化的数学模型,并结合实验数据与模型计算结果,对闭合压力、粒径、支撑剂铺置层数等参数进行了敏感性分析,认为适当增加支撑剂铺置层数和选用较大粒径支撑剂有利于降低压后缝宽变化幅度;最后分析了不同储层弹性模量下支撑剂变形量与嵌入量的相对大小,给出了根据云图图版优选不同弹性模量支撑剂的方法。该研究对加砂压裂施工中的砂比优化和支撑剂类型优选具有一定指导意义。
The embedment of proppant in fracture surface can greatly decrease the conductivities of hydraulic fractures,as well as the productivity. The field practices have validated the design of proppant multilayer pattern in the fractures which can effectively relieve the negative effect of proppant embedment and deformation. Most of existing models of proppant embedment are based on the square single-layer pattern of proppant arrangement,which is so idealized that can not accurately compute the fracture conductivity when proppant embedment is considered. The rhombic multi-layer pattern of proppant arrangement is taken into account,in order to better analyze the impact of proppant embedment on fracture aperture. Elastic mechanics and Hertz theory are first introduced to accurately calculate the proppant's strain under the closure,and then the mathematical model for calculating propped fracture width is established. The experimental data and the calculating results are combined to analyze the sensibilities of closure pressure,proppant diameter and the number of proppant layers. The results show that more proppant layers and larger diameter proppant are beneficial to decrease the depth of proppant embedment. In the end,the extent of proppant deformation and embedment under different reservoir Young's modulus conditions are analyzed,and the optimization method for the proper Young's modulus proppant according to standard plate is presented. The results have great guiding and practical significance in selecting proper type of proppant and optimizing sand concentration.
出处
《科学技术与工程》
北大核心
2018年第6期107-113,共7页
Science Technology and Engineering
基金
四川省青年科技创新研究团队专项计划(2017TD0013)
国家自然科学基金重大项目(51490653)资助
关键词
支撑剂嵌入
支撑剂变形
支撑缝宽
弹性力学
闭合压力
数学模型
proppant embedment
proppant deformation
popped fracture width
elastic mechanics
closure pressure
mathematical models
