Advanced Materials Research Vol. 772

Abstract: Temperature gradient and solidification rate are two key parameters during polysilicon directional solidification, which are varied to improve the polysilicon production process. Dendritic growth, distribution of impurities, Minority carrier lifetime and resistivity mapping are also discussed in this paper. A better quality of polysilicon ingot is presented by optimized casting process.

Abstract: This paper summarizes the development process of wind turbines control technology, reviews the application of traditional control, sliding mode variable structure control, H robust control, adaptive control, fuzzy control, artificial neural network control and integrated control in the pitch angle control system of variable pitch wind turbines, points out its present situation and development prospect.

Abstract: The tests of domestic In-Situ Combustion began in 1960s, with smaller and slower development. The technology has been further developed in recent years. There are five pilot projects, which increase more than 60,000 tons of crude oil. X block of Xinjiang Oil Field has been ignited since December of 2009. With the development of the In-situ Combustion technology, the use of analysis of produced fluids is very necessary, which provide theoretical basis for the commencement of the next steps. We can draw conclusion through the analysis of produced fluids: the success of ignition; the adequacy of combustion; reactions at high temperature or low temperature; the forward direction and location of fire front. Analysis of produced fluids for Xinjiang Oil Field determine clearly the ignition is successful and the way forward of the fire-drive front.

Abstract: Fractured-horizontal well can effectively reduce the percolation resistance near wellbore, improve the fluid mobility and enhance the production. However, in Chang 6 ultra-low permeability reservoir, BaiBao block, HuaQing oilfield, the efficiency of fractured-horizontal well is highly poor due to the production swiftly down and water cut sharply up. For studying the unsatisfying oil development by fractured-horizontal well in HuaQing oil field, the evaluation of reservoir properties and the option of stratum for fractured-horizontal well application have been performed based on the practical geological model of BaiBao block in HuaQing oil field. The numerical simulation is used to study the effect of reservoir permeability, Thickness and Aeolotropism on the production and to optimize the horizontal length, fracture spacing, half length and conductivity. The conclusion shows that Chang 6₃ stratum is qualified for fractured-horizontal well application. Through the practical geological model, the optimizations of horizontal length range, fracture spacing, half length and conductivity are 800m to 1200m, 77m, 150m, and 15μm²cm, respectively. The results can be conducted for fractured-horizontal well application in HuaQing oil field.

Abstract: The future of the energy sector in the coming years is expected to be significantly affected by unconventional gas resources. Flow through porous media has many applications in the chemical, petroleum, gas, and pulp and paper industries, as well as in soil remediation and material characterization. In petroleum and natural gas production, flow through porous media has significance in the production of gas and/or oil. There are many characteristics of tight reservoir rock resulting in high and complex water saturation such as tiny pore throat, poor sorting, high displacement pressure, and so on. The one hand, the gas seepage is affected by the slippage effect, resulting in the abnormal gas relative permeability. On the other hand, the residual water of the tight core is controlled by displacement pressure. This study is directly related to gas reservoir engineering and is specifically focused to obtain fundamental information for two phase flow through low permeability porous media (Tight Sand Gas).

Abstract: The statistical analysis of constant elements of red mudstones in the lower part of the fourth member of Shahejie Formation (S₄) in Dongying Depression shows that the red mudstones in the lower S₄ of Dongying Depression can be classified into three major types based on the characteristics of their constant elements, which is closely relevant to the sedimentary structures of red mudstones. Among the three types of red mudstones, two types originate from one single source area while the other type embraces the characteristics of multi-sources.

Abstract: Most hydrocarbon absorption attenuation studies are based on poststack seismic data processing but, because of multiple stacks at full angle, poststack data will lose some lithology and hydrocarbon-bearing capacity information. To overcome this disadvantage, a prestack angle-domain absorption attenuation analysis technique can be performed for seismic data stacked at various angles to obtain angle-domain-dependent absorption profiles. The absorption anomaly reflects the gas-bearing reservoir and also decreases as the angle increases. Actual data from the Sulige gas field, Ordos Basin, have been processed, and the hydrocarbon predictions match very well with actual drilling results, validating the method's effectiveness.

Abstract: Coalbed gas, also called coalbed methane gas, is a kind of unconventional natural gas located in coal and rocks, coexisting with coal and its main ingredient are methane. On different levels of structure, coal bed methanes adsorption has partition zonality. The gas-bearing of coal seams has relative concentration in different tectonic units, is known as coalbed methane (CBM) enrichment. Influenced by coal rank, coal, rock properties and various geological conditions and other factors, the enrichment has certain regularity. In the study of the coal bed gas enrichment, coal bed gas enrichment especially refers to coal bed methane enrichment. Economic evaluation is that it may analysis reserves financial feasibility and economical rationality for coal seam to get the best economic benefit evaluation, by various stages in CBM cost and final production and income situation.

Abstract: Stress-sensitivity effects have been recognized to have impact on the pressure/rate transient behavior of wells in several reservoirs. Although the effects of stress-sensitivity have been considered in well testing theory in the past thirty years, little has been done to determine their influence on rate decline behavior. This paper presents a single phase flow model considering stress-sensitive formation permeability to investigate the characteristic of production rate decline of a vertical well. The stress-sensitive permeability is considered as an exponential form. The permeability changes with pressure drop are described by a permeability modulus. By introducing two pseudo functions, the equations of the mathematical model are linearized and approximate semi-analytical solutions are obtained. The analytical solutions are carefully verified through numerical simulation. Two sets of new decline type curves are diagramed on a log-log plot for constant rate case and constant bottomhole pressure case respectively. The influence of stress-sensitive permeability on decline curves are analyzed and compared. From this work, we recognized that the rate decline characteristics of stress-sensitive reservoir under constant rate and constant bottomhole producing condition are different. New analysis method should be developed to analyze field variable rate/variable pressure drop data.

Abstract: This paper takes Yingtai area which is located in the south of Qijia-Gulong sag and part of central sag area in the north of the Songliao Basin as the research area. Then combining all information of core, logging, three-dimensional seism and well testing data, it studies the reservoir type and oil-water distribution characteristics of Heidimiao by analyzing the comparison charts of sandstone, profile map of reservoir, T₀₇ structure diagram, well testing data, stratum thickness, sandstone thickness, ratio of sandstone thickness to stratum thickness, porosity values, permeability contour maps. The reservoir lithology of Heidimiao oil layer is siltstone-oriented with poor physical property. The main controlling factor of oil-water distribution is the lithology, followed by the structure. Heidimiao oil layer mainly includes three types, lithological oil reservoir, lithological - structural oil reservoir and structural oil reservoir, among which lithological reservoir plays a dominant role. Its oil-water distribution is characterized by the pattern of upper-water and bottom-oil; when the fault acts as the pathway for the longitudinal migration of oil and gas, the pattern changes to the upper-oil and bottom-water. This research could provide reliable geological basis for the research of old well re-examination, favorable area evaluation and horizontal well drilling design.