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Water exists in shale gas reservoirs in the form of connate water and retained fracturing fluid. The nanoscale interaction between gas and water plays an important role in gas transport in shale na...

Establishment of productivity equation is an important premise for rational and efficient development of low-permeability condensate gas reservoir and accurate analysis of production performance. Based on two-phase seepage mechanism of gas and condensate oil in formation, the productivity equation is established considering threshold pressure, stress sensitivity, slippage effect, retrograde condensate effect and high-velocity non-Darcy effect. The integrals of pseudo-pressure, turbulence factor and pseudo-threshold pressure are calculated with numerical method to resolve the productivity equation. Example calculation results indicate that with the decrease in bottom hole pressure, the increase in condensate gas well production rate is near linear first and then the increase is getting slower and slower. Slippage effect increases apparent permeability and condensate gas well productivity. Retrograde condensate effect, stress sensitivity and threshold pressure decrease apparent permeability and condensate gas well productivity. Based on orthogonal experiment design, the sensitive parameters influencing the productivity of low-permeability condensate gas well are analyzed. Various factors have different influence degrees on gas well productivity in different ranges of bottom hole pressure. Research results lay a theoretical foundation for taking measures to improve gas well productivity in the gas field.

Condensate oil and water invasion coexist in the condensate gas reservoir with bottom water. Because of influences of condensate oil pollution and water invasion, gas recovery obviously decreases. ...

Water-soluble gas reservoirs have the characteristics of high temperature and high pressure (HTHP) and experience obvious pressure-sensitive effects during the production process. Therefore, the influences of formation water and dissolved natural gas in formation water on water-soluble gas reservoirs are different from conventional gas reservoirs. In view of this, this work first carried out a stress sensitivity test with irreducible water and variable internal pressure at high temperature for a water-soluble gas reservoir, showing that permeability loss ratio and effective stress have an exponential relationship, a result basically consistent with conventional tests. However, the stress sensitivity test result with irreducible water was greater than the stress sensitivity test result without irreducible water; porosity decreased slightly with increasing confining pressure, and the total decrease ratio was less than 5.2%, with an average of 3.01%. Second, a high-pressure, high-temperature, nuclear magnetic resonance (NMR) online detection system was introduced to detect the pore signal of core samples under different effective stress states, and pore compression and deformation characteristics were evaluated. Results show large pores to have been compressed slightly more than small pores, pores to be significantly compressed in the initial stage, and the greater the increase in effective stress, the more obvious the compression. Third, the occurrence and characteristic changes of irreducible water in the process of rock compression were detected by the NMR online system, indicating irreducible water to be difficult to migrate through compression in water-soluble gas reservoirs under slight compression of rock and pore structure and the occurrence and characteristics of irreducible water to have not changed significantly. Finally, by establishing a theoretical model of water-soluble gas reservoirs to simulate the water breakthrough of gas wells under stress sensitivity conditions, this work shows that when stress sensitivity exists, gas-well water breakthrough time is earlier and production is diminished.

Complex fracture systems including natural fractures and hydraulic fractures exist in shale gas reservoir with fractured horizontal well development. The flow of shale gas is a multi-scale flow process from microscopic nanometer pores to macroscopic large fractures. Due to the complexity of seepage mechanism and fracture parameters, it is difficult to realize fine numerical simulation for fractured horizontal wells in shale gas reservoirs. Mechanisms of adsorption–desorption on the surface of shale pores, slippage and Knudsen diffusion in the nanometer pores, Darcy and non-Darcy seepage in the matrix block and fractures are considered comprehensively in this paper. Through fine description of the complex fracture systems after horizontal well fracturing in shale gas reservoir, the problems of conventional corner point grids which are inflexible, directional, difficult to geometrically discretize arbitrarily oriented fractures are overcome. Discrete fracture network model based on unstructured perpendicular bisection grids is built in the numerical simulation. The results indicate that the discrete fracture network model can accurately describe fracture parameters including length, azimuth and density, and that the influences of fracture parameters on development effect of fractured horizontal well can be finely simulated. Cumulative production rate of shale gas is positively related to fracture half-length, fracture segments and fracture conductivity. When total fracture length is constant, fracturing effect is better if single fracture half-length or penetration ratio is relatively large and fracturing segments are moderate. Research results provide theoretical support for optimal design of fractured horizontal well in shale gas reservoir.

In high-temperature, high-pressure (HTHP), water-soluble gas reservoirs, a significant amount of natural gas is dissolved in the formation water. During development, with changing reservoir pressure, the natural gas in the formation water will be released. The released natural gas will carry the formation water to form gas-liquid two-phase flow into the porous media of the gas reservoir, which results in premature water breakthrough, thus changing the law of formation water invasion. In order to determine the influence of water-soluble gas on formation water invasion, it is important to study the water-soluble gas content of water-soluble gas reservoirs. Based on experimentation and existing modeling, a prediction model was established for water-soluble gas content in HTHP water-soluble gas reservoirs, and the influence of water-soluble gas content on water invasion was studied. From the results, the following conclusions can be drawn. (a) The content of water-soluble gas increases with increasing pressure, first decreasing and then increasing with increasing temperature. (b) In addition to temperature and pressure, the factors affecting the content of water-soluble gas include the gas components and the mineralization degree of formation water. (c) The existing prediction model has the problems of large error and inconsistency with the measured value, (average error being 33.92%), especially lacking consideration of how changing carbon dioxide content in the gas composition affects the water-soluble gas content. (d) Considering the influences of temperature, pressure, gas components, and formation water mineralization on the prediction model of water-soluble gas reservoirs, the calculation results of the model are more in line with the actual circumstances of gas reservoirs, with the average error being 6.81% and the accuracy of water-soluble gas content prediction being increased five times. (e) Through case analysis, it is shown that the release of water-soluble gas has a great impact on the water breakthrough law of gas wells. Considering the water-soluble gas, the water breakthrough time of gas wells is relatively early. Results show that the water-soluble gas content prediction model for HTHP water-soluble gas reservoirs can predict the water-soluble gas content of water-soluble gas reservoirs more accurately, laying a foundation for understanding the water invasion law of water-soluble gas reservoir development and developing such a gas reservoir efficiently.

It is important that the tight gas reservoir is developed with test wells in the first place for the reasonable development, and it is necessary evaluation production index of test well. So, the paper will evaluate gas wells capacity, reasonable production, production decline law and producing reserves. Combining with calculation theory, comparison of adjacent wells and field practice, obtained reasonable production, production decline law and production reserves about test well, and through analysis the adjacent well obtained development experience and lessons about tight gas reservoir. The results show that the gas well development should pay attention to reasonable production and prevent energy falling too fast in tight gas reservoirs, The decline rule of wells with long production time should be analyzed by two stages. Through study, it will provide some reference and guidance for the development of gas wells in tight gas reservoirs.

A snake well is a complex well type and meanders in a sinusoidal pattern through multiple drainage areas provided by multiple isolated production zones. Conventional productivity calculation methods for horizontal wells could not be applied directly for snake wells because the production segments in the wellbore have large vertical fluctuation and wellbore pressure drop is noticeable. Starting from the distribution of velocity potential produced in an infinite reservoir by one snake well, this paper uses mirror image and the principle of superposition to obtain velocity potential and pressure distributions in bottom water drive reservoirs with and without gas cap, and edge water drive reservoir. Flow characteristics along the wellbore are then investigated and a pressure drop model is developed. Coupling the flow inside wellbore and in the reservoir, we developed and further solved a productivity prediction model for the snake well. The proposed approach to calculating well productivity better meets the reality and results in more accurate prediction. Case studies in bottom water drive reservoir with and without gas cap, and edge water drive reservoir show that snake wells with small fluctuation rates yield higher productivities than horizontal well. Also, permeability anisotropy has less impact on the productivity of snake well than that of horizontal well. For the reservoir with low vertical permeability, snake well can perform better than horizontal well.

The function of capillary pressure in the process of CO displacement in low-permeability reservoir is researched through combination of indoor experiments and numerical simulation. On the basis of different displacement experiments in long core chamber, one-dimensional numerical simulation component model is built to research the function of capillary pressure under the different CO displacement ways. The results show that the capillary pressure under the different CO displacement ways is not consistent. Capillary pressure is the driving force in the process of CO displacement while resistance force in the process of CO pressure buildup and displacement. In order to promote reasonable and efficient development of low-permeability reservoirs, it is suggested that further study about microscopic effects and laws of the capillary pressure in the reservoir should be done through experiment.

Die service life improvement is an important problem in high-pressure die casting industry. Former studies show that biomimetic laser remelting process provides desirable microstructural and microhardness changes, which induces the intensified particles for improving the service life. The present study concerns laser surface remelting of H13 tool steel in a quenched and tempered state using an Nd:YAG laser. This purpose is to obtain data for establishing database of laser parameters for H13 material, which is helpful for applying laser remelting on die casting dies. The influence of laser parameters on the characteristics of the unit has been investigated. The interrelationships among the laser processing parameters, the penetration depth, the width, and the area of the unit were discussed by single-factor experiments. A set of die casting die was selected and processed by laser remelting, and the die service life has been increased from 13,000 shots to 27,000 shots under practical die casting conditions.

Die service life improvement is an important problem in high-pressure die-casting industry. Die service life, which is defined as the maximum product number produced before it fails, and die performance directly determine the production cost and quality of die-casting product. To reduce the repair and maintenance costs, an approach to prevent die from thermal damage and prolong the die lifetime is required. Biomimetic laser-remelting process (BLRP) provides a promising method to improve the service life of die-casting mold. However, the laser processing regions can only be determined by experiences. In order to determine the exact laser processing regions for a set of new die before BLRP, a combination system of CAE and BLRP is proposed in this paper. Through analyzing the mold filling process and the temperature distribution, potential thermal cracks are worked out by numerical simulation system, which are the laser processing regions. The method proposed in this paper advances the efficiency of the BLRP. And practical production validates the veracity and the reliability of the method.

Die service life improvement is an important problem in high-pressure die-casting industry. As many factors affecting the service life, die service life improvement is a systematic project. In this paper, a cover die-casting die was investigated in order to increase its life time. Different die materials, computer-aided engineering (CAE) analysis, biomimetic laser-remelting process, and die structure optimization are adopted in order to enhance its performance. The die service lives are traced for dies of different die materials (H13 and SKD61). The die service lives are compared for dies with/without structure optimization with the help of CAE simulation. The application shows that CAE simulation is a useful tool for die structure optimization. Experiment result on SKD61 die steel after laser-remelting process shows that biomimetic laser-remelting process provides desirable microstructural and microhardness changes in biomimetic units, which induces the intensified particles for improving the service life.

Die service life improvement is an important problem in high-pressure die-casting industry. Experiment results on die steel shows that biomimetic laser-remelting process provides a promising method to improve the service life of die-casting die. A casting with uneven wall thickness was selected and problems existing in die-casting production were analyzed. The corresponding die-casting die was processed by biomimetic laser-remelting process. The application result indicates that the service life of the die processed by biomimetic laser-remelting process has been increased from 12,000 to 28,000 shots, which is more than twice that of no processed one under real high-pressure die-casting conditions. The application of laser-remelting process provides desirable micro-structural changes in biomimetic units, which induces the intensified particles effect for improving the service life.

Punches and dies are the real operating components and account for a large portion in the progressive die design procedure. This paper presents a structural design tool for punches and dies for progressive dies of motor core based on functional component. The descriptive model of punch and die component is established which contains three aspect of information, geometry information, assembly-related constraint attribute and hole-related information on plates. Based on the classification and 3D modeling method of punches and dies, the library of components for punches and dies is set up according to the descriptive model. Methods for modeling and data management for components of punches and dies are discussed in detail. The proposed tool for progressive die for motor cores can complete the design of five classes of punches and dies and generate holes on plates automatically. This design tool is constructed on a PC and integrated with a SolidWorks CAD system. The progressive die design for the motor core of house appliance is employed as a practical example to demonstrate the effectiveness of the design tool. The results reveal that it can dramatically improve the design quality and can save both time and costs.

Chunguang oilfield is a lithologic trap reservoir with edge water drive, whose horizontal well development effect is influenced by static factors and dynamic factors. In the process of production, the influences of static factors including reservoir physical properties and dynamic factors including working system, liquid production velocity on horizontal well development effects are different, and it is difficult to find main factor influencing horizontal well development effect with conventional single-factor analysis method. Combined with static and dynamic data of Chunguang oilfield, using multi-factor grey correlation analysis method, quantitative relationships between horizontal well development effect and different factors are systematically analyzed. Main factors influencing horizontal well development effect and dynamic influence laws between different factors and horizontal well development effect are clarified. Problems existed in the development process are known and it can provide the direction for future development and adjustment of Chunguang oilfield.

OBJECTIVE: To explore the expression of intercellular adhesion molecule-1 (ICAM-1) in hepatic stellate cells (HSC). METHODS: Via in situ perfusion with proteinase and collagenase and density-gradient centrifugation with Nycodenz, HSC were isolated and cultured from the livers of both normal Wistar rats and the livers of rats treated with carbon tetrachloride. Expression of ICAM-1 in HSC was detected by an immunohistochemistry assay and reverse transcription–polymerase chain reaction (RT-PCR). RESULTS: No ICAM-1 was expressed in the freshly isolated HSC of normal rats, but ICAM-1 was found in primary cultures of HSC at day 10 and in secondary cultures of HSC at day 7. Additionally, the intensity of the expression increased over time. Expression of ICAM-1 was observed in freshly isolated HSC from the livers of rats treated with carbon tetrachloride. CONCLUSIONS: Expression of ICAM-1 is related to the activation of HSC, hepatic inflammation and hepatic fibrogenesis.

The gear sleeve is the key part of automobile and motorcycle. The top cavity is the small module involute internal gear with addendum modification and many teeth, the gear form is narrow, the tooth tip is pointed. The bottom is taper hole with three notchs, and the concentricity between the top and bottom is high. So, mechanical cutting of the sleeve is difficult, and plastic forming is difficult too. To meet the needs of markets and improving comprehensive function of automobile and motorcycle, the high efficiency cold precise forming technology of net-shaping for the gear sleeve is put forward based on analysis, study and repeated test. In the same time, a set of high accuracy die with simple novel structure and long service life is designed and manufactured. The advantage of the method has been verified that material utilization and production efficiency is high. For this reason, the technology of the cold precise forming is profitable reference for producing of the same type gear sleeve.