Applied Mechanics and Materials Vols. 295-298

Abstract: In order to investigate the pyrolysis characteristics of oil shale under in the extreme conditions of high temperature and high pressure generated by the ultrasonic cavitation. The different particle size of oil shale is mixed with water in accordance with the volume ratio of 1:12, under in different ultrasonic frequency and different power, the ultrasonic radiation experiments and the thermogravimetric experiments of different samples have been done. The results show that the organic content of oil shale samples reduced after ultrasonic radiation, and the chemical reaction rate of the remaining organic matter become faster, and its reflected as the volatile separate out rate was accelerated and the changes of TG(Thermogravimetry) and DTG(Derivative Thermogravimetry) curves were steeper. Oil shale pyrolysis weight loss rate peak values and the organic matter decomposed percentage during the pyrolysis have the selective on the ultrasonic frequency, ultrasonic power and particle size of the oil shale. Oil shale pyrolysis weight loss rate peak value increased with decreasing of ultrasonic power, and the weight loss rate peak value corresponding to the peak temperature was increased with the increasing of ultrasonic frequency, and the weight loss rate peak value corresponding temperature decreased with particle size increasing of oil shale. We can draw the conclusion that the ultrasonic cavitation can decomposition organic matter of oil shale, then, we should in-depth research the ultrasonic refining shale oil.

Abstract: Interpreting the remaining oil saturation in polymer flooding reservoir is very important for the oil exploration and development. Based on the original physical model of Archie formula, a kind of remaining oil saturation interpretation method for the polymer flooding reservoir is proposed, on the analysis of the variation rules of Archie parameters caused by the polymer influences in the reservoir microscopic pore structure, conductivity and wettability in this article. Theoretical analysis and actual applications show that Archie formula is still applied to calculate the remaining oil saturation for polymer flooding reservoir. This formula form is simple, easy to calculate the parameters, the interpretation accuracy can satisfy the practical development needs, and can be widely used for polymer flooding reservoir.

Abstract: For testing the feasibility of in-situ exploring oil shale by underground coal gasification. Based on the specification analysis of coal and oil shale, through simulating the occurrence state and characteristics of coal and oil shale, the underground Co-gasification model test was carried-out. In different gasification conditions (φ(O2) are 30%、35%、40%、45%、50% and oxygen/steam) ,The temperature-field extend rules of coal and oil shale、the separate-out rules of oil shale production and influence of oil shale on the quality of gas were studied. The results show that: when φ(O2) is 40-45%, temperature-rising rate is 7°C/min、extend rate of gasification face is 0.036m/h, the extend of temperature field is continuous and stable, the temperature change of oil shale and coal are synchronously , the high temperature of oil shale can up to 1000 °C above, that can satisfied the requirement of oil-gas collecting; and the same time , The heat-value of syngas improved 26.37%; The technological parameter was obtained in this test.

Abstract: As one of the most important displacements in producing petroleum, CO2 flooding has been developed for nearly 50 years around the world in order to improve the tertiary recovery. The recovery efficiency, R, is a key parameter in the CO2 displacement of crude oil. Traditionally, R is determined by conducting CO2 flooding experiment, requiring considerable resources and long time periods, with the consequence of a limited number of core plug evaluations for a particular reservoir. Thus, the estimation of R with mathematical models is developed in recent years, which also needs plenty of relevant parameters considered. The study reported in this paper uses artificial neural network to determine R. Five dimensionless variables are considered to analyse the CO2 immiscible displacement process. An optimal model is chosen with its suitable hidden layer nodes and activation functions for the hidden and output layers. Its performance is compared with the numerical simulation model, demonstrating the superior performance of the proposed R prediction model.

Abstract: Bayes confidence limit for domestic drilling mud pump piston life was given. Maximum likelihood estimation of mud pump piston life was discussed under Weibull life distribution. For further, failure mechanism of the same batch mud pump piston was studied, the shape parameter of Weibull distribution was considered to be constant. Bayes point estimation and confidence limit of distribution parameters and mud pump piston life were given, according to field life data collected from Daqing oil field, under non-information priori and conjugate prior information for scale parameter. Example shows the effectiveness of the proposed method.

Abstract: In order to study the effect of CO2 dissolving in formation water on the process of CO2 injection, a thermodynamic model of CO2-hydrocarbon-formation water has been used to study the dissolving law of CO2 in formation water and oil-gas-water phase behavior considering the CO2 dissolution in formation water. Based on compositional model considering the dissolution of CO2 in formation water, a dimensional model for long core CO2 displacement is presented to simulate the oil displacement efficiency, gas/oil ratio, oil or gas saturation profile, the solubility of CO2 in in-place oil or formation water with grid distance in the process of long core displacement of CO2 injection. The results show that the solubility of CO2 in formation water increases with increasing pressure and decreases with increasing temperature, and that the solubility of CO2 in formation water is usually about 5.5 wt% at the condition of reservoir pressure and temperature. In addition, oil saturation and gas phase saturation with the consideration of CO2 dissolving in formation water lag behind those without consideration of CO2 dissolution, which results in later breakthrough time for CO2 injection. Moreover, residual oil saturation with considering CO2 dissolving in formation water is higher than that without considering CO2 dissolution at the condition of the same hydrocarbon pore volume for CO2 injection, and the ultimate recovery for the former is lower than that for the latter when pouring into 0.3 hydrocarbon pore volume of CO2.

Abstract: Production of superheated steam huff and puff wells is affected by reservoir geological characteristics (effective thickness, net gross ratio), the state of development (recovery degree, integrated water-cut) and steam injection parameters (intensity of steam injection, steam injection rate, temperature and degree of superheat. etc.). On the basis of analysis of each factor, All factors set were established by a new specified model and the weight of each factor was determined by the functional correlation between the factors and production of each well. The integrated measured value of all factors was calculated by dimensionless value of each factor through integrated evaluation methods. Statistics results showed that the oil production of each well has perfect proportional relationship with the integrated measured value of all factors, there is the higher the integrated measured value of all factors, the higher the oil production of each well. According to this good correspondence, the integrated evaluation template was formed, and the total coincidence reached 96% with high reliability in the practical application in the Kenkiyak Oilfield, Kazakhstan.

Abstract: The interaction between n-alkanes and pour point depressants with different structures was investigated. Using n-hexadecane as the representative component of crude oil n-alkanes, molecular simulation was employed to study the interaction between polyacrylate pour point depressants with different side chain length and n-hexadecane, and the interaction between polyacrylate pour point depressants with different polar building blocks and n-hexadecane. It was shown that during wax precipitation process, the mixed energy is low when the side chain length of acrylate is compatible with n-hexadecane. It is easier for polyacrylate to go into wax-crystal lattice, thus lowering crude oil pour point. The simulation for pour point depressants consisting of acrylate and other different polar building blocks demonstrated that the stronger the polarity of polar building block, the lower the interaction energy between polymer pour point depressant and n-hexadecane. At the same time, it is easier for polymers with polar building blocks to interact with n-alkanes. The polar building block can effectively inhibit wax-crystal growth and thus improve crude oil low-temperature fluidity.

Abstract: Taking the example of the fourth member of the Lower Cretaceous Quantou formation reservoirs in fault block Sheng554 of Sanzhao sag, this article discusses the methodology of flow units in extra-low permeability reservoirs. The research on flow units in such reservoirs can be divided into two ranks, one is to determine the distribution of seepage barriers and inner connected sands， the other is to analyze the differentia of fluid flow in the inner connected sands so as to subdivide the flow units. The result shows that the pelitic barriers are rather developed in fault block Sheng554. Through the analysis of differentia of fluid flow, according to the value of flow zone index (FZI), the inner connected sands can be classified into three types of flow units, among which type A with FZI value greater than 1.0 has better permeable property and higher intensity of water injection, and the ability of permeability and water injection of type B with FZI value between 0.5 and 1.0 takes the second place, and type C is the worst flow unit with the worst permeable property and intensity of water injection with FZI value less than 0.5. Among the three types of flow units, type A poorly develops, while type B and type C develops well. The research on flow units can provide reliable geologic bases for forecasting the distribution of remaining oil in extra-low permeability reservoirs and for developing remaining oil in the study area.

Abstract: Multi-stage hydraulic fracturing in horizontal wells has been more widely adopted for shale gas development. Fracturing cost control is the key point to guarantee shale gas development benefit. Currently, valuation standard of fracturing in shale gas large horizontal well has not been introduced in China. Based on conventional gas fracturing standard, which cost is determined by scale increasing, fracturing cost in shale gas is fairly high and is inconformity with the practical situation. This paper analyzes the characteristics of the horizontal wells fracturing and differences of 8 technical and economic parameters of the fracturing engineering in conventional gas. The advantages and disadvantages and the application scope of three models, bill of quantities, quota valuation and total charge, are compared. And these models have been commonly used in fracturing engineering valuation at home and abroad. Valuation methods of combining on bill of quantities and quota valuation are put forward which are suitable for the present stage of shale gas development. The key valuation parameters of fracturing in shale gas horizontal wells are studied. Four control measures about the technical research, the standard establishment, the design optimization and the market competition are discussed. The research has a positive significance to speed up the shale gas resources development and improve the investment efficiency.