鄂尔多斯盆地苏里格气田储层次生孔隙性质与分布预测

Permian reservoir in Sulige area of Ordos Basin, on which this paper focused, belongs to fluvial-delta lithofacies. The majority formations in this area are complicated channel sand deposit with serious inhomogeneity which makes natural gas exploration be very tough in this area. This inhomogeneity can be found everywhere both in large horizontal area and vertical profile of inner and interbedded formations.This paper studied the inhomogeneity characteristic of Permian formation in sulige area of Ordos Basin according to the logging data.Correlating with core data, a criterion to distinguish different type of reservoirs by using logging data is determined after the study of logging response is done considering the diverse conditions of deposit environments, lithology and reservoir space. The characteristic relationships between the various type formations and logging responses fully and systemically are established.It investigated reservoir parameter calculation methods amply. Combining the conventional and special logging data, basing on the feature of low porosity -permeability formation of sulige area, a set of methods to calculate reservoir parameters was formed including primary porosity, secondary porosity, fracture porosity, permeability and water saturation under the conditions of both low porosity-permeability and inhomogenous reservoirs. One thing should be pay close attention is the parameter M for calculating saturation. It is found that the M in low porosity -permeability formation decreases as the porosity decrease, which is opposite to the law that M increases as the porosity decrease in the formation with intermediate to high porosity and permeability. This view has innovated the traditional theory and offered theory basis for the logging interpretation of low porosity - permeability reservoir. Meanwhile it also improved the Arqi formula theoretically and enhanced the logging interpretation accuracy and rescued a number of formations which has been thought to be hopeless according to the old theory.By using advantage logging interpretation procedure, a territorial synthetic geology evaluation to the inhomogeneous reservoir was completed basing on the single well interpretation. All the reservoir evaluation parameters including sand formation thickness, primary porosity, secondary porosity were calculated and evaluated. The rules of changing and development for sand formation thickness, sand physical properties and secondary porous were found at different formations of upper part of the Member 8 of Shihezi, lower part of the Member 8 of Shihezi, the Member 1 of shanxi and the Member 2 of shanxi individually. Evaluation and Correlation of these five formations were also completed and one conclusion was arrived: upper part of the Member 8 of Shihezi formation has the best performance followed by the lower part of the Member 8 of Shihezi, the Member 1 of shanxi and the Member 2 of shanxi formation.After studied the relationship between reservoir deposition characteristic and the natural gas richness, it is regarded that reservoir inhomogeneity is the key issue of the impaction on the natural gas. Natural gas in Sulige gas field was mainly accumulated in sands of channel bar, distributary channel and debouchure bar. Especially, the quartz sand with rich of secondary porous space has obvious better physical properties than other reservoir and usually can forms the concentration of natural gas.

Numerical Simulation of Nox Formation in Coal Combustion with Inlet Natural Gas Burning

A full two-fluid model of reacting gas-particle flows and coal combustion is used to simulate coal combustion with and without inlet natural gas added in the inlet. The simulation results for the case without natural gas burning is in fair agreement with the experimental results reported in references. The simulation results of different natural gas adding positions indicate that the natural gas burning can form lean oxygen combustion enviroment at the combustor inlet region and the NOz concentration is reduced. The same result can be obtained from chemical equilibrium analysis.

Analysis of Temperature and Pressure Changes in Liquefied Natural Gas (LNG) Cryogenic Tanks

Liquefied natural gas (LNG) is being developed as a transportation fuel for heavy vehicles such as trucks and transit buses, to lessen the dependency on oil and to reduce greenhouse gas emissions. The LNG stations are properly designed to prevent the venting of natural gas (NG) from LNG tanks, which can cause evaporative greenhouse gas emissions and result in fluctuations of fuel flow and changes of fuel composition. Boil-off is caused by the heat added into the LNG fuel during the storage and fueling. Heat can leak into the LNG fuel through the shell of tank during the storage and through hoses and dispensers during the fueling. Gas from tanks onboard vehicles, when returned to LNG tanks, can add additional heat into the LNG fuel. A thermodynamic and heat transfer model has been developed to analyze different mechanisms of heat leak into the LNG fuel. The evolving of properties and compositions of LNG fuel inside LNG tanks is simulated. The effect of a number of buses fueled each day on the possible total fuel loss rate has been analyzed. It is found that by increasing the number of buses, fueled each day, the total fuel loss rate can be reduced significantly. It is proposed that an electric generator be used to consume the boil-off gas or a liquefier be used to re-liquefy the boiloff gas to reduce the tank pressure and eliminate fuel losses. These approaches can prevent boil-off of natural gas emissions, and reduce the costs of LNG as transportation fuel.

Simulation of Natural Gas Production in Hydrate Reservoirs

This paper simulates a one-dimensional physical model of natural gas production from hydrate dissociation in a reservoir by depressurization. According to the principles of solid hydrate decomposition in stratum and flow of natural gas in porous medium, the pressure governing equations for both gas zone and hydrate zone are set up based on the physical production model. Using the approximation reported by N. N. Verigin et al. (1980), the nonlinear governing equations are simplified and the self-similar solutions are obtained. Through calculation, for different reservoir parameters, the distribution characters of pressure are analyzed. The decline trend of natural gas production rate with time is also studied. The simulation results show that production of natural gas from a hydrate reservoir is very sensitive to several reservoir parameters, such as wellbore pressure and stratum porosity and permeability.

Effect of microwave on formation/decomposition of natural gas hydrate

Natural gas hydrate (NGH) reservoirs have been considered as a substantial future clean energy resource and how to recover gas from these reservoirs feasibly and economically is very important. Microwave heating will be taken as a promising method for gas production from gas hydrates for its advantages of fast heat transfer and flexible application. In this work, we investigate the formation/decomposition behavior of natural gas hydrate with different power of microwave (2450MHZ), preliminarily analyze the impact of microwave on phase equilibrium of gas hydrate,and make calculation based on van der Waals-Platteeuw model. It is found that microwave of a certain amount of power can reduce the induction time and sub-cooling degree of NGH formation, e.g., 20W microwave power can lead to a decrease of about 3A degrees C in sub-cooling degree and the shortening of induction time from 4.5 hours to 1.3 hours. Microwave can make rapid NGH decomposition, and water from NGH decomposition accelerates the decomposition of NGH with the decomposition of NGH. Under the same pressure, microwave can increase NGH phase equilibrium temperature. Different dielectric properties of each composition of NGH may cause a distinct difference in temperature in the process of NGH decomposition. Therefore, NGH decomposition by microwave can be affected by many factors.

An industrial scale dehydration process for natural gas involving membranes

An industrial scale dehydration process based on hollow fiber membranes for lowering the dew point of natural gas is described in this paper. A pilot test with the feed flux scale of 12x10(4) Nm(3)/d was carried out. Dew points of -8 degreesC-13 degreesC at a gas transport pressure in the pipeline of 4.6M Pa and methane recovery of more than 98% were attained. The water vapor content of the product gas could be maintained around 0.01 vol% during a continuous run of about 700 hours. The effects of feed flux and operation pressure on methane recovery and water vapor content were also investigated. Additionally, some auxiliary technologies, such as a full-time engine using natural gas as fuel and the utilization of vent gas in the process, are also discussed. A small amount of the vent gas from the system was used as a fuel for an engine to drive vacuum pumps, and the heat expelled from the engine was used to warm up the natural gas feed. The whole system can be operated in a self-sustainable manner from an energy point of view, and has a relatively high efficiency in the utilization of natural gas.