Rare earth complexes of Eu³⁺ and Nd³⁺ with pyridine dicarboxylate [Ln(2,6?dipic)(2,6?Hdipic)(H₂O)₂]?4H₂O (Ln: Eu, Nd) were synthesized by hydrothermal method. The structure, magnetism and thermodynamic properties of the complexes were studied by the means of single crystal X?ray diffraction measurement, magnetic test, thermogravimetric analysis and differential scanning calorimetry analysis. The results show that two complexes are isostructural crystallizing in the monoclinic system of space group P2₁/c. There are two different coordination modes for pyridine?2,6?dicarboxylic acid in the crystals. The complexes exhibit antiferromagnetism with obvious orbital coupling effect. The prepared complexes have good thermal stability.

The strong stress sensitivity of low permeability oilfield reservoirs leads to serious permeability loss,larger starting pressure gradient,and higher seepage resistance,thereby reducing the water?flooding effects of oilfields.The existing prediction models for water breakthrough time do not consider the stress sensitivity and variable starting pressure gradient at the same time,which results in inconsistency between calculation results and actual situation of mines.Therefore,for the first time,this paper deduced the prediction models for the water breakthrough time of well pattern of five point method,four point method,and inverse nine point method in the condition of unequal row spacing and well spacing considering stress sensitivity and variable starting pressure gradient.The calculation results show that the error of the new model is relatively small,which is more in line with the field practice.The results can guide the adjustment of block measures and provide theoretical support for improving the development of water drive oilfields.