An analysis method of injection and production dynamic transient flow in a gas field storage facility

A dynamic transient flow analysis method considering complex factors such as the cyclic injection and production history in a gas field storage facility was established in view of the limitations of the existing methods for transient flow analysis and the characteristics of the injection-production operation of strongly heterogeneous gas reservoirs, and the corresponding theoretical charts were drawn. In addition, an injection-production dynamic transient flow analysis model named "three points and two stages" suitable for an underground gas storage(UGS) well with alternate working conditions was proposed. The "three points" refer to three time points during cyclic injection and production, namely, the starting point of gas injection for UGS construction, the beginning and ending points of the injection-production analysis stage;and the "two stages" refer to historical flow stage and injection-production analysis stage. The study shows that the dimensionless pseudo-pressure and dimensionless pseudo-pressure integral curves of UGS well flex downward in the early stage of the injection and production process, and the dimensionless pseudo-pressure integral derivative curve is convex during the gas production period and concave during the gas injection period, and the curves under different flow histories have atypical features. The new method present in this paper can analyze transient flow of UGS accurately. The application of this method to typical wells in Hutubi gas storage shows that the new method can fit the pressure history accurately, and obtain reliable parameters and results.

A Study on Remediation Technologies for Cadmium Contamination in Greenhouse Vegetable Fields

Based on the literature and experimental results, three kinds of amendments, namely, rice biochar, hydroxyapatite and potassium dihydrogen phosphate(KH2PO4), and deeper ploughing were selected to evaluate the field application effect of soil amendments and agronomic measures on the remediation of Cd contamination in greenhouses. Cd-contaminated greenhouse screening was conducted from 2015 to 2017. In September 2017, comparative tests of eight treatments were performed in September 2017, and a selective test was performed in September 2018. The results of the screening of contaminated areas indicated that the distributions of over-standard sites and Cd content were significantly different. Greenhouse No. 4, in which the highest over-standard rate was 83.33% and the average content of Cd in soil was 0.535 mg/kg, was used as a comparative test experimental site for eight treatments. Greenhouse No. 1 was selected as the optimum test greenhouse for selective testing, with three plots having average Cd concentrations of 0.530, 0.568 and 0.792 mg/kg. The 8 months following comparative treatment showed that the content of available Cd following the treatment of rice biochar+hydroxyapatite+deeper ploughing(treatment T6) was reduced by 32.55% and 24.96% compared with the CK(the control) and 2 months following treatment, respectively. The content of available Cd using rice biochar+KH2PO4+deeper ploughing(treatment T7) treatment decreased by 47.88% and 31.00% compared with the CK and 2 months following treatment. The selective test results showed that in rice biochar+hydroxyapatite+deeper ploughing: the total Cd content of decreased from 0.489 to 0.372 mg/kg(23.86% lower), compared with the CK, and the mean content of available Cd decreased by 10.71% after 8 months, which was the lowest available Cd measured(0.133 mg/kg). In addition, the bean plant Cd content, bioconcentration factor(BCF) and translocation coefficient(TF) decreased by 15.86%, 23.68% and 25.77%, respectively. Rice biochar+hydroxyapatite+deeper ploughing is a favoured technology for the remediation of Cd-contaminated protected vegetable fields.