A Well Productivity Model for Multi-Layered Marine and Continental Transitional Reservoirs with Complex Fracture Networks

Using the typical characteristics of multi-layered marine and continental transitional gas reservoirs as a basis,a model is developed to predict the related well production rate.This model relies on the fractal theory of tortuous capillary bundles and can take into account multiple gas flow mechanisms at the micrometer and nanometer scales,as well as the flow characteristics in different types of thin layers(tight sandstone gas,shale gas,and coalbed gas).Moreover,a source-sink function concept and a pressure drop superposition principle are utilized to introduce a coupled flow model in the reservoir.A semi-analytical solution for the production rate is obtained using a matrix iteration method.A specific well is selected for fitting dynamic production data,and the calculation results show that the tight sandstone has the highest gas production per unit thickness compared with the other types of reservoirs.Moreover,desorption and diffusion of coalbed gas and shale gas can significantly contribute to gas production,and the daily production of these two gases decreases rapidly with decreasing reservoir pressure.Interestingly,the gas production from fractures exhibits an approximately U-shaped distribution,indicating the need to optimize the spacing between clusters during hydraulic fracturing to reduce the area of overlapping fracture control.The coal matrix water saturation significantly affects the coalbed gas production,with higher water saturation leading to lower production.

Hydraulic Fracture Parameter Inversion Method for Shale GasWells Based on Transient Pressure-Drop Analysis during Hydraulic Fracturing Shut-in Period

Horizontal well drilling and multi-stage hydraulic fracturing are key technologies for the development of shale gas reservoirs.Instantaneous acquisition of hydraulic fracture parameters is crucial for evaluating fracturing effectiveness,optimizing processes,and predicting gas productivity.This paper establishes a transient flow model for shale gas wells based on the boundary element method,achieving the characterization of stimulated reservoir volume for a single stage.By integrating pressure monitoring data following the pumping shut-in period of hydraulic fracturing for well testing interpretation,a workflow for inverting fracture parameters of shale gas wells is established.This new method eliminates the need for prolonged production testing and can interpret parameters of individual hydraulic fracture segments,offering significant advantages over the conventional pressure transient analysismethod.The practical application of thismethodology was conducted on 10 shale gaswellswithin the Changning shale gas block of Sichuan,China.The results show a high correlation between the interpreted single-stage total length and surface area of hydraulic fractures and the outcomes of gas production profile tests.Additionally,significant correlations are observed between these parameters and cluster number,horizontal stress difference,and natural fracture density.This demonstrates the effectiveness of the proposed fracture parameter inversion method and the feasibility of field application.The findings of this study aim to provide solutions and references for the inversion of fracture parameters in shale gas wells.

Thyroxine treatment for elderly patients with heart failure and sick euthyroid syndrome

Objectives To evaluate the effect of thyroid hormone therapy with low dose of thyroxin on cardiac function in elderly patients with heart failure and sick euthyroid syndrome.Methods Forty-seven patients(33 males and 14 females,mean age 85.9+4.6 years,ranging from 80 to 99 years)with chronic heart failure(NYHAⅡ-Ⅳ)and low triiodothyronine(T_(3))state were randomly allocated to the treatment group or control group.The treatment group patients received oral administration of levothyroxine sodium(Euthyrox)25-50mg/d in addition to conventional therapy of heart failure,whereas patients in control group were given conventional therapy only.Serum level of total T_(3)(TT_(3)),free T_(3)(FT_(3)),total thyroxine(TT_(4)),free thyroxine(FT_(4)),and thyroid-stimulating hormone(TSH)were determined.For both groups,left ventricular ejection fraction(LVEF)and stroke volume(SV)were assessed by two-dimensional echocardiography before and at 8 weeks after treatment.The changes of these parameters after the treatment were evaluated by adjusting heart rate in the two groups.Results The reduced serum T_(3) level in the treatment group was corrected after thyroid hormone therapy,and these patients had a significant improvement in cardiac function after treatment.By contrast,in the control group only changes of serum TT_(3) and TT_(4) levels and SV and LVEF after treatment were statistically significant.The heart rate-adjusted mean SV and LVEF in both groups were also increased,which was significantly greater in the treatment group than in the control group.Conclusion In the elderly patients with heart failure and sick euthyroid syndrome,addition of thyroxine at a low dosage to the conventional treatment could effectively improve the low T_(3) state and cardiac function independent of changes of heart rate.

Scaffold-based tissue engineering strategies for soft-hard interface regeneration

Repairing injured tendon or ligament attachments to bones(enthesis)remains costly and challenging.Despite superb surgical management,the disorganized enthesis newly formed after surgery accounts for high recurrence rates after operations.Tissue engineering offers efficient alternatives to promote healing and regeneration of the specialized enthesis tissue.Load-transmitting functions thus can be restored with appropriate biomaterials and engineering strategies.Interestingly,recent studies have focused more on microstructure especially the arrangement of fibers since Rossetti successfully demonstrated the variability of fiber underspecific external force.In this review,we provide an important update on the current strategies for scaffold-based tissue engineering of enthesis when natural structure and properties are equally emphasized.We firstly described compositions,structures and features of natural enthesis with their special mechanical properties highlighted.Stimuli for growth,development and healing of enthesis widely used in popular strategies are systematically summarized.We discuss the fabrication of engineering scaffolds from the aspects of biomaterials,techniques and design strategies and comprehensively evaluate the advantages and disadvantages of each strategy.At last,this review pinpoints the remaining challenges and research directions to make breakthroughs in further studies.

Improved Fixed-Time Convergence Guidance Scheme Design and Its Application to Missile

This study presents a fixed-time convergence guidance scheme for impact time and angle control.First,two improved fixed-time stable systems are presented,which have smaller initial control command and better terminal convergence.16 An improved fixed-time extended state observer is proposed to provide accurate estimation of system states and disturbance,which effectively solves peaking value problem.Furthermore,an improved fixed-time sliding mode controller is derived,which avoids the singular problem and achieves faster convergence rate with smaller initial control command.Second,a new guidance scheme with impact angle and impact time constraints is proposed for intercepting a stationary target.By introducing a virtual target,the guidance process is divided into two stages.The proposed fixed-time controller is employed in the first stage.The method with a virtual leader ensures that the missile intercept the virtual target with desired line-of-sight angles at a specific time.By using the proportional navigation guidance law,the missile keeps travelling with desired flight-path angles to hit the real target in the second stage,17 so as to achieve the impact time and angle control.Finally,the feasibility and effectiveness of the proposed guidance scheme in different engagement scenarios are verified by numerical simulations with comparisons.