In Jilin Oilfield, development of water-flooding operations in tight oil reservoirs is not satisfactory due to low effective permeability, tiny pore throats, and low mobility of crude oil in the matrix. In the interest of improving water-flooding efficacy for tight oil reservoirs, researchers in this study developed one nanofluid permeation flooding system through microemulsion preparation. This paper presents the experiments evaluating the characteristics and mechanism of improving tight oil recovery using nanofluids. The study results demonstrate that (1) the nanofluid permeation flooding system, with an average particle size of <25 nm, is very stable under the reservoir conditions and can effectively expand the swept volume ratio of the matrix with low porosity and ultralow permeability; (2) under the flow condition, the system can split the tight oil in Jilin Oilfield into "oil droplets in nanosize" which can be easily displaced from the matrix, with both swept volume and oil displacement efficiency exceeding 90% according to the micro etching model; and (3) the system has a good interfacial activity, leading to an interfacial tension with the tight oil in Jilin Oilfield of up to 10 −1 mN/m, so that it can greatly promote the efficacy of oil displacement in the matrix with tiny pores. According to the flooding experiments with cores retrieved from the oilfield, the nanofluid permeation flooding system with a concentration of 0.3% improves the oil displacement efficiency of water flooding by more than 27% averagely and reduces the injection pressure by over 38%. NMR evaluation results of tight cores indicate that the flooding system allows crude oil to be more efficiently displaced from meso/micropores. The nanofluid permeation flooding system is presumed to effectively improve the swept volume and oil displacement efficiency of water flooding and replenish formation energy. It can be a great support for efficient water-flooding development and continuous enhanced oil recovery in tight oil reservoirs of Jilin Oilfield.

Long core flow experiment was conducted to study problems like excessive injection pressure and effective lag of oil wells during the polymer flooding in Honggang reservoir in Jilin oilfield. According to the changes in viscosity and hydrodynamic dimensions before and after polymer solution was injected into porous media, the compatibility of polymer hydrodynamic dimension and the pore throat size was studied in this experiment. On the basis of the median of radiusRof pore throats in rocks with different permeability, dynamic light scattering method (DLS) was adopted to measure the hydrodynamic size Rh of polymer solution with different molecular weights. The results state that three kinds of 1500 mg/L concentration polymer solution with 2000 × 104, 1500 × 104, and 1000 × 104molecular weight matched well with the pore throat in rocks with permeability of 300 mD, 180 mD, and 75 mD in sequence. In this case, the ratios of core pore throat radius median to the size of polymer molecular clewR/Rhare 6.16, 5.74, and 6.04. For Honggang oil reservoir in Jilin, when that ratio ranges from 5.5 to 6.0, the compatibility of polymer and the pore structure will be relatively better.

The relationship between hysterectomy and ovarian preservation and depression is controversial. This study aimed to determine the association of hysterectomy and ovarian preservation with depression using National Health and Nutrition Examination Survey. To assess the association between hysterectomy with or without ovariectomy and depression, we used 3 methods. Method 1: propensity score model (PSM) was established. Method 2 was logistics regression analysis of hysterectomy and depression before and after PSM. Method 3 was a logistics regression analysis of the relationship between hysterectomy and different depressive symptoms. At the same time, in order to evaluate the association between hysterectomy with or without oophorectomy and depression, we explored the effect of four different surgical procedures on depression using logistic regression equations. We enrolled 12,097 women, of whom 2763 underwent hysterectomy, 34.455% were positive for depression. After weighting, 33.825% of the total sample had a PHQ ≥ 5. Finally, a total of 2778 women were successfully matched by propensity score, and 35.537% of them were positive for depression. The OR for PHQ ≥ 5 was 1.236 after crude adjustment of covariates and 1.234 after exact adjustment. This suggests that Hysterectomy is strongly associated with positive depression. Positive depression (PHQ ≥ 5) was associated with little interest, feeling down and trouble concentrating. It was not associated with trouble sleeping, feeling tired, poor appetite, feeling bad, slow moving or speaking, and suicidal thoughts. Oophorectomy-alone is not associated with depression. Hysterectomy-alone is a risk factor for depression, but Hysterectomy combined with Oophorectomy has a stronger correlation with depression than Hysterectomy-alone. Women who have had a Hysterectomy are at higher risk of depression than women who have not had a Hysterectomy, and this risk may be exacerbated if the uterus and ovaries are removed. When clinically appropriate, surgeons should try to preserve the patient's ovaries.