地层水矿化度对硬脆性泥页岩蠕变规律影响的试验研究  

Experimental Study of the Effect of Formation Water Salinity on Creep Laws of the Hard Brittle Shale

作　　者：王萍[1,2] 屈展[1,2] 黄海[2] 

机构地区：[1]西北工业大学航空学院,陕西西安710072 [2]西安石油大学机械工程学院,陕西西安710065

出　　处：《石油钻探技术》2015年第5期63-68,共6页Petroleum Drilling Techniques

基　　金：国家自然科学基金项目"力学与化学耦合下泥页岩井壁蠕变损伤失稳研究"(编号:51174162);陕西省教育厅项目"泥页岩水化损伤的蠕变特性研究"(编号:14jk1575)联合资助

摘　　要：硬脆性泥页岩层理、微裂缝发育,易造成井壁坍塌,特别当受到外来流体侵入时,泥页岩具有明显的流变效应。以硬脆性泥页岩为研究对象,进行了不同矿化度地层水饱和岩样的单轴压缩蠕变试验。在相同的外载条件下,矿化度6.0×104 mg/L地层水饱和岩样的蠕变变形量最小（0.001～0.014）,矿化度8.0×104 mg/L地层水饱和岩样的蠕变变形量稍大（0.005～0.024）,矿化度4.0×104 mg/L地层水饱和岩样的蠕变变形量最大（0.010～0.030）。借鉴经典元件组合模型的建模思路,建立了反映蠕变三阶段的蠕变模型,模型中瞬时弹性模量、黏滞系数和加速蠕变黏滞系数等3个重要参数都明显趋于下降。试验结果表明：矿化度与泥页岩蠕变变形量之间呈二次非线性函数关系,太高或太低都会对泥页岩的力学性质产生较大的影响。研究认为,在现场钻井中应考虑钻井液矿化度对井壁稳定的影响。Hard brittle clay shale has micro-fractured bedding and tends to cause side-wall collapse.Particularly when being invaded by foreign fluids,the rock has obvious rheological effects.Taking hard brittle shale as the object of study,uniaxial creep experiments on water saturation samples of formations with different degrees of mineralization were conducted.Research results showed that under the same externally applied loads,the creep deformation degree of the formation water saturated rock samples with a salinity of 6.0×104 mg/L was the least（0.001-0.014）and the creep deformation degree of the formation water saturated rock samples with a salinity of 8.0×104 mg/L was a little greater（0.005-0.024）,while the creep deformation degree of the formation water saturated rock sample with a salinity of 4.0×104 mg/L was the greatest（0.010-0.030）.Learning from the modeling ideas of classic element combination models,the creep model reflecting three creep stages was established.Three important parameters（instantaneous elastic modulus,viscous coefficient,accelerated creep viscous coefficient）in the model tended to decrease obviously.Test results showed that the relation between rock mineralization and creep deformation degree was quadratic non-linear,and that too high or too low salinity would have the greatest influence on the mechanical properties of rocks.The study suggested that the influences of drilling fluid salinity on borehole wall stability should be considered in drilling operations.

关 键 词：地层水 矿化度 硬脆性 泥页岩 蠕变 实验室试验 

分 类 号：TE21[石油与天然气工程—油气井工程]