摘要
砂堵是严重的工程事故,长期的加砂压裂施工经验认为,通过提高排量可以提升缝内净压力从而增加水力裂缝宽度,以防止砂堵。但在国内某油田的加砂压裂施工中却出现当排量高于一定值以后,反而会比排量较低时更容易形成砂堵的情况。为此,首先归纳总结了形成砂堵的3种主要机理,即储层的地质特性、施工参数与材料的选取不合理、裂缝宽度过窄,分析认为裂缝宽度不足是形成该现象的主要原因;然后在前期研究成果的基础上,建立了同层平行多裂缝和穿隔层裂缝的宽度模型,模拟了排量上升、裂缝宽度减小的现象,分析了模型中各参数的敏感性,认为多裂缝模型中的主控因素是杨氏模量和泊松比,而穿隔层模型中的主控因素是隔层外的最小水平主应力;最后提出了安全压力区的概念,将施工压力稳定在安全压力区内可以预防反常砂堵。该研究成果对于提高裂缝型和薄隔层储层的加砂压裂施工成功率具有重要的指导意义。
From numerous field practices in sand fracturing treatment, we have gained experience of preventing sand plug, a serious engineering accident, by improving the injection rate to increase the net pressure and the width of hydraulic fractures. However, in one failure case in an oil field, sand plug was more likely to occur when the injection rate was higher than a certain value. Hence, three dominant mechanisms for sand plug were first summarized： geological features of the reservoir, inappropriate selection of construction parameters and materials, and excessively narrow width of fractures. According to the relevant analysis, the last one was thought to be the primary cause for that failure case. Then, based on the pervious research results, two models were established re spectively for the same-layer parallel multi-fracture propagation and the inte-layer fracture propagation to simulate the phenomena under the condition of increased injection rate and reduced fracture width, and to analyze the sensibility of all the parameters. The study and analysis results show that the Young＇s modulus and Poisson＇s ratio are the main controlling parameters of the former model and that the minimum horizontal principal stress out of barrier layers is the main controlling parameter of the latter model. In the end, a new concept of safe pressure range is put forward, i. e. , such abnormal phenomenon of sand plug in the said case can be prevented by controlling the construction pressure within the safe pressure range. The study results are of great importance to impro ving the success rate of fracturing treatment especially in those fractured or thin intercalated reservoirs.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2013年第4期56-60,共5页
Natural Gas Industry
基金
国家科技重大专项课题(编号:2011ZX05049-003)
新世纪优秀人才支持计划(编号:NCET-11-1062)
四川省青年科技基金(编号:2012JQ0010)
关键词
水力压裂
砂堵
施工排量
裂缝宽度
多裂缝
断裂韧性
多层模型
数学模拟
hydraulic fracturing
sand plug
injection rate
fracture width
multi fracture
fracture toughness property
multi-layermodel
mathematical simulation
