Experimental study on hydraulic fracturing of soft rocks: Influence of fluid rheology and confining stress
Experimental study on hydraulic fracturing of soft rocks: Influence of fluid rheology and confining stress
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DOI：
10.1016/j.petrol.2006.01.009
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发表时间：
2006-08-01
影响因子：
--
通讯作者：
de Pater, C. J.
中科院分区：
文献类型：
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作者：
Bohloli, B.;de Pater, C. J.
本文对松散岩石水力压裂进行了实验研究，重点研究了不同围应力下不同注入流体对裂缝起裂和扩展的影响机制。因此，开展了一系列参数研究，包括围应力、注入流体类型和注入段几何形状，以探索压裂对这些变量的依赖关系。结果表明，围应力和流体流变对压实砂的压裂行为有较大影响。注入黏性牛顿流体和交联凝胶主要产生与井眼膨胀有关的渗透。注入含石英粉交联凝胶和膨润土浆液后，裂缝明显。在注入液中加入石英粉和膨润土，可以形成清晰的裂缝。这表明流体流变学和流体添加剂对材料的压裂行为有很强的影响。施加围应力的范围为0.5 ~ 20MPa。在高围应力条件下，起裂压力与围压之比在2左右，而在低围应力条件下，起裂压力与围压之比要高得多，平均在10左右。这意味着在浅井中产生裂缝并不容易，因为注入压力应该达到围应力的10倍。(c) 2006 Elsevier b.v.版权所有
This paper presents an experimental study on hydraulic fracturing of unconsolidated rocks focusing on mechanisms of fracture initiation and propagation using different injection fluids at various confining stresses. Thus, a serial of parameter study including confining stress, type of injection fluid and geometry of injection section was carried out to explore the dependency of fracturing on these variables. Results showed strong influence of the confining stress and fluid rheology on the fracturing behaviour of the compacted sand. Injecting viscous Newtonian fluids and cross-linked gel yielded mainly infiltration associated with well bore expansion. Clear fractures were induced when injecting the cross-linked gel containing quartz powder and the bentonite slurry. When adding quartz powder and bentonite to the injection fluid, clear fractures could be created.This implies that the fluid rheology and the fluid additives have strong influence on the fracturing behaviour of material. Range of the applied confining stresses was between 0.5 and 20MPa. At high confining stress, the ratio of fracture initiation pressure to confining pressure was around 2 while at lower confining stress the ratio was much higher averaging around 10. This would imply that it is not much easier to create fractures in shallow well bores since the injection pressure should reach 10 times the confining stress. (c) 2006 Elsevier B.V All rights reserved.