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大庆油田从投入开发到1981年底,油、水井套管损坏井占投产井数的9.8％。套管损坏井的分布规律是:构造高点多而集中;翼部少而分散,东翼少于西翼;断层附近多而一般地区少;水井多而油井少。初步研究认为,套管损坏与断层分布和地层泥岩有密切关系。 高压注水导致套管损坏加剧。主要是:高压层挤压低压层,低压层产生横向流动;高压注水压开油层原生裂缝,引起油层破裂,加剧层间水窜。 断层的现今复活运动对套管损坏十分明显,断层的现今复活必须具备两个条件:第一,断层面充水产生“润滑”,有利于岩块活动。第二,断层两侧地层压力不平衡,达到足以移动岩块的一定能量。 大庆油田萨零组底～萨二组顶泥岩是损坏套管的“危险段”,存在两层膨润土层,富含蒙脱石,遇水体积膨胀可达28～68倍。 利用材料断裂力学原理计算出:水井放喷作业引起疲劳裂纹扩展的压力界限(门槛值)为45大气压。
From the investment and development of Daqing Oilfield to the end of 1981, the casing damage of oil and water wells accounted for 9.8% of the production wells. The distribution pattern of casing damage well is that the structural high points are more and more concentrated; the wing parts are less and scattered, the east wing is less than the west wing; there are many but near normal faults in the fault; Preliminary studies suggest that there is a close relationship between casing damage and fault distribution and formation mudstone. High-pressure water injection led to increased casing damage. Mainly: high pressure layer extrusion low pressure layer, low pressure layer produces lateral flow; high pressure water injection pressure open the primary fracture, causing the oil layer rupture, exacerbate the interlayer water channeling. The current revival of the fault is very obvious for casing damage. The present resurrection of the fault must have two conditions: First, the fault surface should be filled with water so as to be “lubricated”, which is good for rock activity. Second, the formation pressure on both sides of the fault is unbalanced, reaching a certain amount of energy sufficient to move the rock mass. The top mudstone from the bottom of Zaoliao-Sa2 group in Daqing Oilfield is the “dangerous section” of casing damage. There are two layers of bentonite, which are rich in montmorillonite and can expand 28-68 times with water volume. Using the principle of material fracture mechanics, it is calculated that the pressure limit (threshold value) for fatigue crack growth caused by blow-out operation in a well is 45 atm.