Nonlinear flow in low permeability reservoirs: Modelling and experimental verification

The low-permeability reservoirs are of heavy heterogeneity, low permeability, fine oil-water passages, strong resistance during flow, and the significant interaction between solid and liquid interfaces causes the flow of fluid in reservoir deviating from the Darcy’s law. There is no agreement on the interaction between the various factors in seepage process and the influence of seepage law. The boundary layer exists when liquid flow in micro-tubes and nano-tubes, and the boundary layer decreases with the increase of driving force, and the maximum value of boundary layer ratio is equal to 1. Based on the capillary boundal model and the boundary layer theory, a new exponential seepage model for low permeability reservoirs was proposed. Some experiments of water flow with different pressure gradient were carried out in low permeability cores with permeability of 4 to 8 milidarcy in natural rock cores from an oilfield in China, and the nonlinear model is of good agreement with the single-phase water flooding experiments of these cores. The results demonstrate that the physical meaning of each parameter of the new model is clear and it can be applied to describe the nonlinear characteristics of low permeability reservoirs. The large driving force can overcome disadvantages in the developments of low permeability reservoirs.Cited as: Song, F., Bo, L., Zhang, S., Sun, Y. Nonlinear flow in low permeability reservoirs: Modelling and experimental verification. Advances in Geo-Energy Research, 2019, 3(1): 76-81, doi: 10.26804/ager.2019.01.0

Nonlinear flow in low permeability reservoirs: Modelling and experimental verification

The low-permeability reservoirs are of heavy heterogeneity, low permeability, fine oil-water passages, strong resistance during flow, and the significant interaction between solid and liquid interfaces causes the flow of fluid in reservoir deviating from the Darcy’s law. There is no agreement on the interaction between the various factors in seepage process and the influence of seepage law. The boundary layer exists when liquid flow in micro-tubes and nano-tubes, and the boundary layer decreases with the increase of driving force, and the maximum value of boundary layer ratio is equal to 1. Based on the capillary boundal model and the boundary layer theory, a new exponential seepage model for low permeability reservoirs was proposed. Some experiments of water flow with different pressure gradient were carried out in low permeability cores with permeability of 4 to 8 milidarcy in natural rock cores from an oilfield in China, and the nonlinear model is of good agreement with the single-phase water flooding experiments of these cores. The results demonstrate that the physical meaning of each parameter of the new model is clear and it can be applied to describe the nonlinear characteristics of low permeability reservoirs. The large driving force can overcome disadvantages in the developments of low permeability reservoirs

Threshold Pore Pressure Gradients in Water-Bearing Tight Sandstone Gas Reservoirs

Tight gas reservoirs commonly occur in clastic formations having a complex pore structure and a high water saturation, which results in a threshold pressure gradient (TPG) for gas seepage. The micropore characteristics of a tight sandstone gas reservoir (Tuha oilfield, Xinjiang, China) were studied, based on X-ray diffraction, scanning electron microscopy and high pressure mercury testing. The TPG of gas in cores of the tight gas reservoir was investigated under various water saturation conditions, paying special attention to core permeability and water saturation impact on the TPG. A mathematical TPG model applied a multiple linear regression method to evaluate the influence of core permeability and water saturation. The results show that the tight sandstone gas reservoir has a high content of clay minerals, and especially a large proportion of illite–smectite mixed layers. The pore diameter is distributed below 1 micron, comprising mesopores and micropores. With a decrease of reservoir permeability, the number of micropores increases sharply. Saturated water tight cores show an obvious non-linear seepage characteristic, and the TPG of gas increases with a decrease of core permeability or an increase of water saturation. The TPG model has a high prediction accuracy and shows that permeability has a greater impact on TPG at high water saturation, while water saturation has a greater impact on TPG at low permeability

Clinical characteristics and immunogenetics of BCGosis/BCGitis in Chinese children: a 6 year follow-up study.

In this study, the clinical and immunogenetical features in a cohort of Chinese patients with BCGosis/BCGitis were investigated. For the patients with abnormal immunological functions, Sanger sequencing was used to identify the involved genes. There were 74 confirmed cases of BCGosis/BCGitis during 2007-2012. Classified by infected tissues and organs, no cases only had local infection, 39 patients had a regional infection, 21 patients had a distant infection and 14 patients had a disseminated infection. Thirty-two patients (43.2%) had definitive primary immunodeficiency diseases (PID) and chronic granulomatous disease (CGD) is the most common PID (n = 23, accounted for 71.9% of all PID patients). For CGD patients, based on the anti-tuberculosis treatment, administration of rhIFN-γ resulted in better control of BCGosis/BCGitis. The results indicate that PIDs are associated with susceptibility to BCG disease. For children with BCGosis/BCGitis, immune function evaluation is necessary, and IFN-γ treatment for BCGosis/BCGitis patients with CGD is effective

N-3-Substituted Imidazo Quinazolinones: Potent and Selective PDE5 Inhibitors As Potential Agents for Treatment of Erectile Dysfunction

Phosphodiesterase type 5 (PDE5) inhibitors with improved PDE isozyme selectivity relative to sildenafil may result in agents for the treatment of male erectile dysfunction (MED) with a lower incidence of PDE-associated adverse effects. This paper describes the discovery of 14, a PDE5 inhibitor with improved potency and selectivity in vitro compared to sildenafil. This compound shows activity in a functional assay of erectile function comparable to that of sildenafil

Genetic and Evolutionary Analysis of Porcine Deltacoronavirus in Guangxi Province, Southern China, from 2020 to 2023

Porcine deltacoronavirus (PDCoV) has shown large-scale global spread since its discovery in Hong Kong in 2012. In this study, a total of 4897 diarrheal fecal samples were collected from the Guangxi province of China from 2020 to 2023 and tested using RT-qPCR. In total, 362 (362/4897, 7.39%) of samples were positive for PDCoV. The S, M, and N gene sequences were obtained from 34 positive samples after amplification and sequencing. These PDCoV gene sequences, together with other PDCoV S gene reference sequences from China and other countries, were analyzed. Phylogenetic analysis revealed that the Chinese PDCoV strains have diverged in recent years. Bayesian analysis revealed that the new China 1.3 lineage began to diverge in 2012. Comparing the amino acids of the China 1.3 lineage with those of other lineages, the China 1.3 lineage showed variations of mutations, deletions, and insertions, and some variations demonstrated the same as or similar to those of the China 1.2 lineage. In addition, recombination analysis revealed interlineage recombination in CHGX-MT505459-2019 and CHGX-MT505449-2017 strains from Guangxi province. In summary, the results provide new information on the prevalence and evolution of PDCoV in Guangxi province in southern China, which will facilitate better comprehension and prevention of PDCoV

Optimization of Substituted N-3-Benzylimidazoquinazolinone Sulfonamides As Potent and Selective PDE5 Inhibitors

A previous report from these laboratories identified the N-3-benzylimidazoquinazolinone nucleus as a more selective PDE5 inhibitor template compared to the pyrazolopyrimidine of sildenafil. This paper describes in detail the structure-activity relationships of a set of sulfonamide analogues, several of which are both more potent and more selective PDE5 inhibitors in vitro than sildenafil. The synthesis, in vitro enzyme activity and selectivity, and in vitro functional and preclinical pharmacokinetic assessment of molecules in this series are described