薄互层低渗透油藏压裂开发裂缝扩展规律及产能预测研究

发布时间：2018-08-19 08:41

【摘要】：薄互层低渗透储层砂体发育零散、砂泥交互、纵向层数多、厚度薄,压裂裂缝形态复杂、难以控制,进而使得注水效果差,有效动用程度低,单井产量低。对其直井压裂和水平井多级压裂的耦合渗流规律和裂缝扩展规律认识不清,会严重制约薄互层低渗透油藏的有效开发。因此,需针对薄互层压裂裂缝起裂、扩展规律和压裂开发耦合渗流理论进行深入研究。本文开展了三向应力下裸眼水平井压裂物模实验研究：基于薄互层岩心变形破坏特征,建立适用于薄互层井眼起裂判定准则,推导出不同完井方式、不同井型的破裂压力计算方程；针对不同力学特性砂泥交替的薄互层,建立宏观平均意义下的薄互层复合岩体本构方程,推导了薄互层等效弹性参数；引入异材参数,基于Griffith断裂准则和裂缝界面断裂准则,建立薄互层非平面裂缝起裂-扩展准则,实现裂缝在砂泥界面偏转、滑移、突破等复杂扩展形态的描述,揭示了薄互层非平面裂缝起裂-扩展规律。基于等值渗流阻力法和流场划分方法,建立了考虑薄互层纵向非均质性及压裂裂缝非平面特征的压裂直井耦合渗流数学模型,及考虑射孔、裸眼完井和裂缝相互干扰耦合渗流的水平井多级压裂渗流数学模型。针对薄互层整体压裂注水开发,建立了考虑启动压力梯度和压裂裂缝形态的薄互层混合井网压裂三区耦合流动的两相渗流模型,实现了不同储层条件下不同井网压裂裂缝参数的优化。研究结果表明,水平主应力差为10MPa时,水平井井筒方位角60°,易生成两翼对称的横切缝；井斜角、方位角、水平主应力差越小,破裂压力越大；层间应力差5MPa,隔层厚度6m,均不能实现薄互层上下砂体间沟通；净总厚度比越大,裂缝非平面性越强,启动压力梯度越大,变形系数越大,薄互层压裂单井产量越低；当启动压力梯度大于0.01MPa/m以后,对产量的影响显著；当储层渗透率为1～10mD时,裂缝最优导流能力为10～20D·cm;当储层渗透率超过10mD时,裂缝最优导流能力为20～25D·cm。利用本文所建理论模型进行现场应用,为薄互层低渗透油藏的压裂开发提供了理论依据。
[Abstract]:The sand body of thin interbedded low permeability reservoir is scattered, sand and mud are interactive, the number of longitudinal layers is more, the thickness is thin, the fracturing fracture form is complex and difficult to control, which makes the water injection effect is poor, the effective production degree is low, and the production rate of single well is low. It is difficult to understand the coupling percolation law and fracture propagation law of vertical well fracturing and horizontal well multistage fracturing, which will seriously restrict the effective development of thin interbed low permeability reservoir. Therefore, it is necessary to deeply study the fracture initiation, propagation law and coupled seepage theory of fracturing in thin interbed fracturing. In this paper, an experimental study on fracturing model of open hole horizontal well under three direction stress has been carried out. Based on the deformation and failure characteristics of thin interbed core, the criteria for determining borehole initiation in thin interbed have been established, and different completion methods have been deduced. The fracture pressure equation of different well types, the constitutive equation of thin interbed composite rock mass with different mechanical properties of sand and mud alternately, the constitutive equation of thin interbed composite rock mass in the sense of macroscopic average, the equivalent elastic parameters of thin interbed, the introduction of different material parameters, Based on the Griffith fracture criterion and fracture interface fracture criterion, the initiation and propagation criteria of thin interbedded non-plane fractures are established to describe the complex propagation forms of fractures such as deflection, slip and breakthrough at the interface of sand and mud. The law of initiation and propagation of thin interbedded non-plane cracks is revealed. Based on the equivalent percolation resistance method and the flow field partition method, a coupled seepage mathematical model considering the longitudinal heterogeneity of thin interbed and the non-plane characteristics of fractured fractures is established, and the perforation is considered. A mathematical model of multistage fracturing seepage in horizontal wells with mutual interference of open hole completion and fracture. Aiming at the whole fracturing and waterflooding development of thin interbed, a two-phase seepage model considering the starting pressure gradient and fracturing fracture form is established, in which the coupling flow in three areas of fracturing of thin interbed mixed well pattern is considered. The fracture parameters of different well pattern are optimized under different reservoir conditions. The results show that when the horizontal principal stress difference is 10MPa, the shaft azimuth angle of horizontal well is 60 掳, and it is easy to generate symmetrical transverse fractures with two wings, and the smaller the angle, azimuth and horizontal principal stress difference, the greater the fracture pressure. The stress difference between layers is 5MPa, the thickness of interlayer is 6m, and the communication between upper and lower sand bodies in thin interbed can not be realized. The larger the net total thickness ratio, the stronger the non-planarity of fracture, the greater the starting pressure gradient, the greater the deformation coefficient and the lower the production of single well in thin interbed fracturing. When the starting pressure gradient is larger than 0.01MPa/m, the effect on production is significant; when reservoir permeability is 1~10mD, the optimal conductivity of fracture is 10 ~ 20D cm, and when reservoir permeability exceeds 10mD, the optimal conductivity of fracture is 20 ~ 25D cm. The field application of the theoretical model in this paper provides a theoretical basis for the fracturing development of thin interbed low permeability reservoirs.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE357

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