Structure optimization of the organ-pipe cavitating nozzle and its erosion ability test on hydrate-bearing sediments

Cavitating jet is a promising drilling rate improvement technology in both the marine natural gas hydrate (NGH) fluidization exploitation method and the integrated radial jet drilling and completion method. In present study, we aim to improve the efficiency of jet erosion and extracting NGH. With a computational fluid dynamics (CFD) method, the pressure, velocity and cavitation field characteristics of organ-pipe cavitating jet (OPCJ) are analysed. The divergent angle, throat length, and divergent length of OPCJ nozzle are preferred to obtain stronger jet cavitation erosion effect. Laboratory experiments of gas hydrate-bearing sediments (GHBS) erosion by OPCJ and conical jet (CJ) are conducted to compare and validate the jet erosion performance. The impinging models of OPCJ and CJ are constructed to study the impact characteristics. Results show that the preferred values of divergent angle, throat length, and divergent length are 15°, 1d, and 3d, respectively, in present simulation conditions. For GHBS, the OPCJ possesses the advantages of high efficiency and low energy consumption. Moreover, the OPCJ has higher penetration efficiency, while showing equivalent penetration ability compared to CJ. During the impinging process, the OPCJ can induce stronger impact pressure and turbulence effect, and also shows stronger chambering effect and bottom cleaning ability compared to CJ. This study presents the erosion performance of OPCJ and CJ on GHBS, and provides preliminary insights on the potential field applications in NGH exploitation.

The first offshore natural gas hydrate production test in South China Sea

Natural gas hydrates (NGH)is one of key future clean energy resources.Its industrialized development will help remit the huge demand of global natural gas,relieve the increasing pressure of the environment, and play a vital role in the green sustainable growth of human societies.Based on nearly two decades' studying on the reservoir characteristics in the South China Sea (SCS)and the knowledge of reservoir system,the China Geological Survey (CGS)conducted the first production test on an optimal target selected in Shenhu area SCS in 2017.Guided by the "three-phase control"exploitation theory which focused on formation stabilization,technologies such as formation fluid extraction,well drilling and completing, reservoir stimulating,sand controlling,environmental monitoring,monitoring and preventing of secondary formation of hydrates were applied.The test lasted for 60 days from May 10^th when starting to pump, drop pressure and ignite to well killing on July 9^th,with gas production of 3.09×10^5 m^3 in total,which is a world record with the longest continuous duration of gas production and maximal gas yield.This successful test brings a significant breakthrough on safety control of NGH production.

High salt-induced weakness of anti-oxidative function of natriuretic peptide receptor-C and podocyte damage in the kidneys of Dahl rats

Background:Atrial natriuretic peptide(ANP)and its natriuretic peptide receptors A(NPR-A)and C(NPR-C)are involved in the regulation of physiological and pathophysiological process of blood pressure.The present study aimed to determine the role of NPR-C in the development of salt-sensitive hypertension.Methods::The Dahl salt-sensitive(DS)and salt-resistant(DR)rats were used in this study.Animals were matched according to their age and weight,and then placed on either a high-salt(HS,8%)or a normal-salt(NS,0.4%)diet for 6 weeks randomly using random number table.The systolic blood pressure(SBP),plasmatic sodium concentration(PL Na),urinary sodium excretion(UV Na),and serum creatinine concentration(Scr)were measured.The concentration of ANP in blood and tissues(heart and kidney)was detected by enzyme-linked immunosorbent assay.The expression of ANP,NPR-A,and NPR-C in kidney was evaluated with western blot analysis.Regarding renal redox state,the concentration changes in malondialdehyde(MDA),lipofuscin,nicotinamide adenine dinucleotide phosphate(NADPH)oxidase(Nox),and nitric oxide synthase(NOS)in kidney were detected by a spectrophotometric method.The kidney damage was evaluated using pathological techniques and the succinodehydrogenase(SDHase)examination.Furthermore,after an intra-peritoneal injection of C-atrial natriuretic peptide(ANP)4-23(C-ANP 4-23),an NPR-C receptor agonist,the SBP,biochemical values in blood and urine,and renal redox state were evaluated.The paired Student’s t test and analysis of variance followed by the Bonferroni test were performed for statistical analyses of the comparisons between two groups and multiple groups,respectively.Results::The baseline SBP in all groups was within the normal range.At the end of the 6-week experiment,HS diet significantly increased the SBP in DS rats from 116.63±2.90 mmHg to 162.25±2.15 mmHg(t=-10.213,P<0.001).The changes of SBP were not significant in DS rats on an NS diet and DR rats on an NS diet or on an HS diet(all P>0.05).The significant increase of PL Na,UV Na,and Scr related to an HS diet was found in both DS and DR rats(all P<0.05).However,significant changes in the concentration(t=-21.915,P<0.001)and expression of renal ANP(t=-3.566,P=0.016)and the expression of renal NPR-C(t=5.864,P=0.002)were only observed in DS hypertensive rats.The significantly higher desmin immunochemical staining score(t=-5.715,P=0.005)and mitochondrial injury score(t=-6.325,P=0.003)accompanied by the lower SDHase concentration(t=3.972,P=0.017)revealed mitochondrial pathologic abnormalities in podocytes in DS rats with an HS diet.The distinct increases of MDA(t=-4.685,P=0.009),lipofuscin(t=-8.195,P=0.001),and Nox(t=-12.733,P<0.001)but not NOS(t=-0.328,P=0.764)in kidneys were also found in DS hypertensive rats.C-ANP 4-23 treatment significantly decreased the SBP induced by HS in DS rats(P<0.05),which was still higher than NS groups with the vehicle or C-ANP 4-23 treatment(P<0.05).Moreover,the HS-induced increase of MDA,lipofuscin,Nox concentrations,and Nox4 expression in DS rats was significantly attenuated by C-ANP 4-23 treatment as compared with those with HS diet and vehicle injection(all P<0.05).Conclusions::The results indicated that the renal NPR-C might be involved in the salt-sensitive hypertension through the damage of mitochondria in podocytes and the reduction of the anti-oxidative function.Hence,C-ANP 4-23 might serve as a therapeutic agent in treating salt-sensitive hypertension.