射孔参数对非均质砂岩水力压裂裂缝扩展规律的影响

Influence of perforation parameters on propagation laws of hydraulic fracture in heterogeneous sandstones

射孔参数对非常规油气资源储层压裂改造具有重要影响。目前人们对不同射孔参数条件下非均质储层岩石压裂裂缝的扩展机理认识不足,很大程度地制约了水力压裂技术的现场实施。以天然非均质砂岩为对象,运用CT成像、X射线衍射、电子探针等方法,分析天然砂岩内部矿物颗粒的成份、尺寸和空间位置等分布情况,建立砂岩矿物颗粒成分与尺寸和空间位置的对应关系,构建含矿物颗粒的非均质砂岩三维数字模型,模拟分析不同射孔参数下非均质砂岩水力压裂裂缝扩展行为,探讨射孔的密度、方位角、布孔方式、深度、孔径等参数以及矿物颗粒对非均质砂岩水压裂缝空间展布形态和扩展规律的影响,揭示不同射孔参数下非均质砂岩储层压裂裂缝的扩展机理。研究发现:破裂压力随射孔密度、孔径和孔深的增加而降低,随射孔方位角增大而增加,线性布孔下的破裂压力最大。射孔的密度和方位角对压裂裂缝展布形态有重要影响,射孔深度对压裂裂缝扩展方向起一定的控制作用,射孔孔径对压裂裂缝的影响体现在扩展范围上,布孔方式对裂缝的展布形态影响不大。同时,研究表明:矿物颗粒对砂岩压裂裂缝的扩展规律有很大的影响,非均质砂岩更易形成复杂缝网。

Perforation parameters play an important role in the fracturing of unconventional oil and gas resources reservoirs.At present,the mechanism of fractures propagation in heterogeneous reservoirs under different perforation parameters are not clearly understood,which restricts the field implementation effect of hydraulic fracturing technology to a great extent.Based on CT scan,X-ray diffraction and electron probe experiments,the composition,size and spatial location of mineral particles on natural heterogeneous sandstones are analyzed.The relationship among composition,spatial location and size of mineral particles are established.The reconstruction models of heterogeneous sandstones containing mineral particles were constructed.Based on the reconstruction models,a series of numerical simulations of hydraulic fracture propagation on heterogeneous sandstones under different perforation parameters were carried out.The effects of perforation parameters and mineral particles on the spatial distribution and propagation laws of hydraulic fractures in heterogeneous sandstones were analyzed.The perforation parameters contain perforation density,azimuth angle,perforation pattern,perforation depth,and perforation diameter.The fractures propagation mechanisms of heterogeneous sandstones reservoirs were revealed under different perforation parameters.The results show that the fracture pressure decreases with the increase of perforation density,perforation diameter and perforation depth.The fracture pressure increases with the increase of perforation azimuth,and the maximum fracture pressure appears under the linear perforation layout.Perforation density and perforation azimuth have a great influence on the fracture distribution morphology.Perforation depth has a certain control effect on the propagation direction of fracturing fracture.The influence of perforation diameter on fracturing fractures is reflected in the expansion range.Perforation layout way has little effect on the fracture distribution morphology.The mineral particles have a great influence on the propagation law of fracturing fractures in sandstones,and heterogeneous sandstones are more likely to form complex fracture networks.