In hydraulic fracturing and acid fracturing designs，it is necessary to calculate the fluid temperature distribution in a fracture, This paper has developed a fluid temperature field model when leak-off velocity in the wall is constant. It is simpler than Wheeler's and Whitsitt's models(2)(1)，and as accurate as the precise Wheeler's model. It can satisfy the requirements of practical calculations, In this paper are added calculation examples and curves which can be used for reference in practical calculations.
In order to study the friction-wear conditions of mud pump'sliner/piston in operation and search out the whole procedure of the occurence and trowth of piston's destructions as well as its failure, the observation of gracking the destructive procedure of two pistons has been made on a test bed developed by ourselves. Some phenomena have been observed which are very useful for prolonging the life of piston, The failure mechanism of piston is also introduced in this paper, The failure of piston is its losing the sealing ability, The failure of piston results from the alternate effect of various destructions under complex operation conditions, The fundamental reasons which affect the life of piston are the sealing ability，the properties of rubber materials and the lubricant state of piston.
After the expression of stress field near the tip of a crack of the k-thlaminated plate of the composite laminate is substituted into Tsai-Hill Criterion，a formula of evaluating the plastic zone size factor near the tip of a crack of, the k-th laminated plate of the composite laminate is obtained in this paper. Hence, its plastic zone size can be determined，which makes it possible to apply Fracture Mechanics Criterion to the composite laminate.
The problems of limit cycles in second-order recursive digital filters with a rounding off quantizer have been studied more systematically in this paper. The properties of limit cycles have been summarized，the distribution regions of various limit cycles on the coefficient planes(β1，β2)have been pointed out, and the linear stability conditions of second-order recursive digital filters have been derived, All conclusions in this paper have been verified by computer simulations.
In references (1) we have discussed Cauchy problem of the equation, and given an operator series formula for solution of the Cauchy problem.The present paper makes use of the operator series formula to solve the mixed problem of the equation on m-dimensional rectangular parallelepiped.
By observing the flame distribution of a burning flame ring, this experiment vividly shows the condition of the two oppositely travelling wave trains which cohere in the space of the ring and form standing waves, The number of wave crests and wave troughs of the flame varies regularly with the change of frequences of incoming Waves.
This paper deals with our experiments on the measurement of the hydranlic energy imposed on the rock surface of the hole bottom (denoted by “RSHB”). We have established two new theories of the hydraulic programs in design concerning the maximum hydraulic horsepower and impact force on the RSHB. The “black box” theory, which can be effectively used to solve modern engineering problems, has now been primarily introduced in the research of the flow field of the jet bit above the hole bottom. An unique full-scale experiment (i.e. the experiment measuring the hydraulic energy on the RSHB ) has been done to measure directly the hydraulic horsepower and the impact force of the jets beneath a tricone bit striking on the RSHB. Empirical formulae have been developed for calculating the hydraulic horsepower and the impact force on the RSHB. Two new hydraulic programs have been provided which take the maximum hydraulic horsepower and impact force on the RSHB as the design criteria for the optimized hydraulic programs.Under the experimental conditions in this paper, critical values have been obtained, such as the ratio (Rn) of the horsepower distribution for the maximum hydraulic energy on the RSHB and the range of the hydraulic energy decline factor at the standoff distance (135mm, from the nozzle exit to the RSHB). Under the same condition, the optimum flow rate for the maximum hdraulic energy on the RSHB is about 7.5 per cent more than that for the maximum hydraulic energy on the bit nozzle. From the theory and drilling practice, it has been proved that properly increasing the flow rate and pump-horsepower seems to be quite necessary.
Since jet drilling found wide application, continuous research has been carried out as to fully utilizing the bit hydraulic power at the bottom hole. This paper deals with the experimental study technique and the application of fluid flow direction in the flow field. The imperfect flow patterns of vortex, backflow and stagnation are found to be the main factors affecting the bottom hole scavenging efficiency.Improving the bottom hole flow field of a jet bit will increase the rate of penetration and reduce the cost of jet drilling.
The effective acid penetration distance is an important parameter in acid-fracturing treatment design and has treat influence upon the effect of the treatment. The temperature in a fracture and the acid-rock reaction products simultaneously affect the acid penetration greatly. But up to mow, no information concerning this aspect has been published.For satisfying practical requirements of calculation in the treatment design, this paper developes a new mathematical model for reaction of acid flowing in the fracture by taking principal factors affecting the effective penetration of the acid into consideration. This model is combined with the model of temperature distribution in a fracture, the model of velocity field and the model of acid-rock surface reaction kinetics to give their solution simultaneously and a corresponding computer program has been established to give a system calculation. Figures and tables of data on the influences of common ion effect, acid concentration, formation temperature and heat generated by the acid-rock reaction on effective acid penetration distance have been obtained by analyzing and correlating.The computer program and calculations obtained in this paper can be used in practical acid-fracturing treatment design.
Natural gamma-ray loging is one of the conventional loging methods used in petroleum industry. It can be used to identify rock lithology and analyze sedimentary facies quantitatively. This paper mainly describes a methld for quantitative analysis and recognition of fan-deltaic microfacies by means of the natural gamma ray log. Certain computer mathematical methods are adopted to establish the frequency and deviation patterns for the recognition of fan-deltaic sedimentary microfacies. This makes it possible for a computer to recognize and divide microfacies zones, and plot facies relationship maps and make quantitative analysis of sedimentary facies.The method introduced in this paper is of wide practical value in petroleum industry.
A new method for well test analysis has been discussed in this paper. Based on the method, an interactive computeraided well test interpretation software has been developed. The basic functions of the software are its being able to analyze and process various oil/gas well testing data for single/double media automatically and interpret various reservoir basic parameters accurately. Therefore, it is an important tool for recognizing the features and behaviors of wells and reservoirs.
Characteristics are presented of two phase flow imbibition relative pemeability curves with low interfacial tension. It is found experimentally that at a given saturation nonwetting permeabilities for an unconsolidated porous medium (sand pack) are higher than the drainage permeabilities. The contrary happens for consolidated porous media—imbibition nonwetting permeabilbities are smaller than drainage ones. The ezperimental results obtained in this stud are consistent with those obtained by NAAR with high interfacial tension systems.
This paper investigated the delayed fracture characteristics of high strength steel bolts from the viewpoint of fracture mechanics, and presented some ways and precautions to be taken in preventing the bolts from delayed fracture.
