油井水泥环降脆增韧作用机理研究

Research on mechanism of increasing flexibility and decreasing brittleness of cement sheath in oil well

针对油井水泥环井下易脆裂问题,对脆性水泥环破坏的根本原因进行了研究。结果表明,水泥石内部化学键断裂导致内部裂缝的扩展是水泥环后期层间密封性能失效,并诱发环空窜流的主要原因之一。实验研究了外加剂及外掺料对油井水泥石脆性改善的微观作用机制,建立了包括结晶相、凝胶相、粒间充填及粒间搭桥在内的基质塑化设计模型。利用此设计模型开发了多元材料复合增韧水泥石,与常规水泥石相比,其力学形变完整性的保持能力有较大的提高,适应井下工况环境变化的能力得到增强,可满足油气井后期安全开发生产的需要。

The cracking reason of cement sheath in oil well was analyzed. The crack of chemical bond and the propagation of inner fractures in cement stone resulted in the annual flow in the later stage of stimulation and development of oil-gas wells. The experi-ment of active mechanism of additives and material adding into cement stone for controlling brittleness of cement stone in oil-gas wells was carried out. The matrix-plastization design mode for crystalline phase, gel phase, intergranular packing and intergranular bridging was established. This model was used to develop the multi-compound material for decreasing the brittleness and increasing the flexibility of cement sheath. The multi-compound material cement stone was adaptable to down-hole conditions. The integrity of cement sheath can meet the demands of oil and gas development and prolong the production lifetime of oil and gas wells.