Research On Sandstone Borehole Enlargement Mechanisms And Prevention Technology In Lamadian Oil Field

Lamadian Oil Field (shortened as La area) located at northward of Daqing placanticline, because of approaches on the deposit provenance, its reservoir has the characteristic of highly porous and high permeability. In process of well drilling recent years, many wells arises the phenomenon which borehole abnormal enlargement and borehole collapse at high permeability sand zone. The phenomenon of borehole enlargement causes the log to distortion, and exerts to interpretation of porosity and permeability and etc. Moreover borehole enlargement may arouse the complex accident during well drilling, and also the difficulty of the cementing operation will be increased, causes the hole cement quality to be worse.The high permeability sand zone borehole enlargement is the new question which the waterflood oilfield development in later stage, on the mechanisms, it has essential differences with mudstone borehole enlargement and collapsing. In order to study on the mechanism of borehole enlargement and protection techniques in La area, such analysis and research have been done as the following: the research on regularity for change of the formations'property and electric property, comparative analysis on the produced water and the injection water and X ray diffractive analysis on core samples from main formations of oil wells in La area, determination of mechanics parameters of sandstone cores for the first time and research on longitudinal regularities of distribution and variation trend of rock intensity in La area, research on the correlations between mechanics parameters of sandstone and electric property and the establishment of mathematical model, putting forward the theory and methods of predicting low-cementation areas according to fluid penetrating velocity and development of the predicting software, research on preventing enlargement in high-permeability sandstone, on collapse drilling techniques and on cementing techniques in big borehole intervals.It is concluded that the sedimentary features and exploiting mode of La area have made the injection water produce a destroying effect on formations and have caused borehole enlargement and collapse in sandstone interval of La area in Placanticline Oilfield. The contents of solid particles of the produced water are higher than those of the injection water obviously, which shows the destroying effect of the injection water on formations is mainly washing action currently and the injection water has a strong washing and schlepping effect on clay mineral. The sandstone intensity of La area is comparatively lower, and areas with strong permeation velocity are easily led to borehole enlargement and collapse. Areas with low sandstone intensity can be predicted by calculating penetrating velocity.According to core sample of Lamadian Oil field in this thesis, mechanics parameter determination,longitudinal distribution rule of rock intensity,change tendency have been studied. For the first time sandstone mechanics parameter,electrical relevant research and mathematical model have been established. According to fluid seepage velocity forecasting principle and method of sandstone low cemented region has been provided. In this thesis, according to mechanism analysis result, developing has been prevented the sandstone bore hole expansion,caving in well drilling craft and big bore hole section well cementation processing technology research work. After 30 well field applications, the good effect has been obtained.In this engineering research process has utilized domain oil-field development, geophysics, oil field chemistry theories and the methods and so on. In order to solve the oil field well drilling production actual problem to play the vital role. This technology has certain academic value and the application value.