人工裂缝复杂程度的压裂液返排表征方法及应用

发布时间：2019-04-24 16:57

【摘要】：为评价非常规储层体积压裂后人工裂缝的复杂化程度,基于储层基质与压裂液存在离子交换现象,分析返排液中盐浓度差异的表示方法,建立了体积改造后返排液中盐浓度的饱和度分布数学模型,分析了不同返排液中盐浓度与裂缝复杂化特征关系。结果表明:压后返排液中盐浓度变化主要表现出"平稳型"和"升高-平稳型",返排液初期流体主要以人工裂缝内的单相流为主,返排液中盐的浓度随着返排量的增加而增加,达到一定返排率后,出现2种特征:一是平缓型特征,即返排液中盐的浓度逐渐趋于平稳,表明储层改造后的人工裂缝与储层基质中的离子交换较少,人工裂缝趋向于单一裂缝为主的特征;二是升高-平稳型特征,即返排液中盐的浓度仍存在增加趋势,表明改造后人工裂缝与储层基质产生大量离子交换,并且交换的体积较大,盐浓度随返排液量增大而增加的时间越长,表明人工裂缝的复杂化程度越高。经现场应用并结合微地震等试验手段验证表明,该方法可判别非常规油气井压后人工裂缝的复杂化程度,为进一步优化体积压裂设计提供参考。
[Abstract]:In order to evaluate the complexity of artificial fractures after unconventional reservoir volume fracturing, based on the existence of ion exchange between reservoir matrix and fracturing fluid, the expression method of salt concentration difference in backflow fluid is analyzed. A mathematical model for the saturation distribution of salt concentration in the effluent after volume modification is established, and the relationship between the salt concentration and the characteristics of fracture complication in different backflow fluids is analyzed. The results show that the change of salt concentration in the liquid after pressure is mainly "stable" and "elevated-stable", and the initial fluid is dominated by single-phase flow in artificial fracture, and the results show that the change of salt concentration in the liquid after pressure is mainly composed of "stable" and "elevated-stable". The concentration of salt in the return liquid increases with the increase of the return rate. After reaching a certain return rate, there are two characteristics: one is the flat type characteristic, that is, the salt concentration in the backflow liquid gradually tends to be stable. The results show that the artificial fracture and the ion exchange in the reservoir matrix are less, and the artificial fracture tends to be the main feature of the single fracture. The other is that the salt concentration in the liquid is still increasing, which indicates that there is a large amount of ion exchange between the artificial fracture and the reservoir matrix after modification, and the volume of the exchange is large. The longer the salt concentration increases with the increase of backflow, the more complicated the artificial crack is. Field application and micro-seismic tests show that this method can distinguish the complexity of artificial fractures after fracturing in unconventional oil and gas wells, and provide reference for further optimizing the design of volume fracturing.
【作者单位】：中国石油集团科学技术研究院;中国石油华北油田公司;
【基金】：国家科技重大专项“储层改造关键技术及装备”(编号:2016ZX05023)
【分类号】：TE357.12

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