Gas-Water Production of a Continental Tight-Sandstone Gas Reservoir under Different Fracturing Conditions

A numerical model of hydraulic fracture propagation is introduced for a representative reservoir(Yuanba continental tight sandstone gas reservoir in Northeast Sichuan).Different parameters are considered,i.e.,the interlayer stress difference,the fracturing discharge rate and the fracturing fluid viscosity.The results show that these factors affect the gas and water production by influencing the fracture size.The interlayer stress difference can effectively control the fracture height.The greater the stress difference,the smaller the dimensionless reconstruction volume of the reservoir,while the flowback rate and gas production are lower.A large displacement fracturing construction increases the fracture-forming efficiency and expands the fracture size.The larger the displacement of fracturing construction,the larger the dimensionless reconstruction volume of the reservoir,and the higher the fracture-forming efficiency of fracturing fluid,the flowback rate,and the gas production.Low viscosity fracturing fluid is suitable for long fractures,while high viscosity fracturing fluid is suitable for wide fractures.With an increase in the fracturing fluid viscosity,the dimensionless reconstruction volume and flowback rate of the reservoir display a non-monotonic behavior,however,their changes are relatively small.

Microscopic experiment on efficient construction of underground gas storages converted from water-invaded gas reservoirs

Based on the microfluidic technology,a microscopic visualization model was used to simulate the gas injection process in the initial construction stage and the bottom water invasion/gas injection process in the cyclical injection-production stage of the underground gas storage(UGS)rebuilt from water-invaded gas reservoirs.Through analysis of the gas-liquid contact stabilization mechanism,flow and occurrence,the optimal control method for lifecycle efficient operation of UGS was explored.The results show that in the initial construction stage of UGS,the action of gravity should be fully utilized by regulating the gas injection rate,so as to ensure the macroscopically stable migration of the gas-liquid contact,and greatly improve the gas sweeping capacity,providing a large pore space for gas storage in the subsequent cyclical injection-production stage.In the cyclical injection-production stage of UGS,a constant gas storage and production rate leads to a low pore space utilization.Gradually increasing the gas storage and production rate,that is,transitioning from small volume to large volume,can continuously break the hydraulic equilibrium of the remaining fluid in the porous media,which then expands the pore space and flow channels.This is conducive to the expansion of UGS capacity and efficiency for purpose of peak shaving and supply guarantee.

Influence of depressurization rate on gas production capacity of high-rank coal in the south of Qinshui Basin, China

A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher.

Experimental study on gas production and solution composition during the interaction of femtosecond laser pulse and liquid

The process of ionizing normal saline induced by femtosecond laser is studied from the perspective of gas production rate and composition.When the repetition rate is less than 1000 Hz,each laser pulse independently generates ionization gas.At the same time,we discovered the inhibitory effect of meglumini diatrizoici on the ionization process and explained the reasons for this inhibition.Finally,the gas composition proved that the primary gas production mechanism of the femtosecond laser is the decomposition of water molecular,and the composition of the solution after the reaction proved the decomposition effect of the laser on meglumine.

Gas evolution characteristics of three kinds of no-bake resin-bonded sands for foundry in production

No-bake resin-bonded sand is commonly used in casting production.However,its air pollution is relatively serious,especially in the molding and pouring process.For this reason,it is necessary to study the gas evolution characteristics of no-bake resin-bonded sand from room temperature to high temperatures,and not only the amount of gaseous products,but also the composition of the gaseous products.No-bake furan resin-bonded sand(#1),phenolic urethane no-bake resin-bonded sand(#2),and alkaline phenolic no-bake resin-bonded sand(#3)are the three most common no-bake resin-bonded sands in casting.The gas evolution volume and rate of these three no-bake resin-bonded sands were studied.Thermogravimetry-mass spectrometer(TG-MS),headspace-gas chromatography/mass spectrometer(HS-GC/MS),and pyrolysis-gas chromatography/mass spectrometer(PY-GC/MS)were used to measure the composition of the gaseous products emitted from binders at room temperature and high temperatures.The differences between formaldehyde,heterocyclic aromatic compounds(HAC),monocyclic aromatic hydrocarbons(MAH),and polycyclic aromatic hydrocarbons(PAHs)gaseous products from the three types of no-bake resin-bonded sands during the molding and casting process were compared.From the perspective of environmental protection,alkaline phenolic no-bake resin-bonded sand and no-bake furan resin-bonded sand are better than phenolic urethane no-bake resin-bonded sand.

Maximizing the Benefit of Rate Transient Analysis for Gas Condensate Reservoirs

In recent years,many trials have been made to use the Rate Transient Analysis(RTA)techniques as a method to describe the gas condensate reservoirs.The problem with using these techniques is the multi-phase behavior of the gas condensate reservoirs.Therefore,the Pressure Transient Analysis(PTA)is commonly used in this case to analyze the reservoir parameters.In this paper,we are going to compare the results of both PTA and RTA of three wells in gas condensate reservoirs.The comparison showed a great match between the results of the two mentioned techniques for the first time using a reference GOR of 75,000 SCF/STB.Therefore,we concluded that we could depend on RTA instead of PTA to spare the cost associated with the PTA in the gas condensate reservoirs.

Study on Influencing Factors of Methane Production Efficiency of Microbial Electrolytic Cell with CO_(2) as Carbon Source

Reducing CO_(2) to produce methane through microbial electrolytic cell(MEC)is one of the important methods of CO_(2) resource utilization.In view of the problem of low methanogenesis rate and weak CO_(2) conversion rate in the reduction process,theflowfield environment of the cathode chamber is changed by changing the upper gas cir-culation rate and the lower liquid circulation rate of the cathode chamber to explore the impact on the reactor startup and operation and products.The results showed that under certain conditions,the CO_(2) consumption and methane production rate could be increased by changing the upper gas recirculation rate alone,but the increase effect was not obvious,but the by-product hydrogen production decreased significantly.Changing the lower liquid circulation rate alone can effectively promote the growth of biofilm,and change the properties of biofilm at the later stage of the experiment,with the peak current density increased by 16%;The methanogenic rate decreased from the peak value of 0.561 to 0.3 mmol/d,and the CO_(2) consumption did not change signifi-cantly,which indicated that CO_(2) was converted into other organic substances instead of methane.The data after coupling the upper gas circulation rate with the lower liquid circulation rate is similar to that of only changing the lower liquid circulation rate,but changing the upper gas circulation rate can alleviate the decline of methane pro-duction rate caused by the change of biofilm properties,which not only improves the current density,but also increases the methane production rate by 0.05 mmol/d in the stable period.This study can provide theoretical and technical support for the industrial application scenario offlowfield regulation intervention of microbial elec-trolytic cell methanogenesis.

Numerical investigation on the effect of gas parameters on ozone generation in pulsed dielectric barrier discharge

Pulsed dielectric barrier discharge is a promising technology for ozone generation and is drawing increasing interest. To overcome the drawback of experimental investigation, a kinetic model is applied to numerically investigate the effect of gas parameters including inlet gas temperature, gas pressure, and gas flow rate on ozone generation using pulsed dielectric barrier discharge. The results show that ozone concentration and ozone yield increase with decreasing inlet gas temperature, gas pressure, and gas flow rate. The highest ozone concentration and ozone yield in oxygen are about 1.8 and 2.5 times higher than those in air, respectively. A very interesting phenomenon is observed： the peak ozone yield occurs at a lower ozone concentration when the inlet gas temperature and gas pressure are higher because of the increasing average gas temperature in the discharge gap as well as the decreasing reduced electric field and electron density in the microdischarge channel. Furthermore, the sensitivity and rate of production analysis based on the specific input energy （SIE） for the four most important species 03, O, O（1D）, and O2（b1∑） are executed to quantitatively understand the effects of every reaction on them, and to determine the contribution of individual reactions to their net production or destruction rates. A reasonable increase in SIE is beneficial to ozone generation. However, excessively high S1E is not favorable for ozone production.

Temperature Sensitivity of Soil Respiration Probed by Numerical Analysis of Field-Observed Data Sets

Temperature sensitivity of soil respiration is essential to predict possible changes in terrestrial carbon budget on various scenarios about atmospheric and soil climates. Although it is often evaluated by using respiratory quotient “Q10”, Q10 values of soil respiration seem to vary depending on methods or scales of evaluation. Aiming at probing how Q10 values of soil respiration are evaluated differently for a field, this study used a model of soil respiration rate, and numerically evaluated soil respiration rates along depth by fitting the model to depth distributions of CO2 concentration measured in a field. And temperature sensitivity of soil respiration rate was evaluated by comparing the determined soil respiration rates with atmospheric and soil temperatures measured in the field. The results showed that the relation between surface CO2 emission rates and atmospheric temperatures was represented by lower Q10 values than that between soil respiration rates and soil temperatures, presumably because the top soil layers had acclimatized in more extent to the existing thermal regime than the underlying deeper layers. Thus, for evaluating effects of long-term rise in atmospheric temperature on soil respiration, it is necessary to precisely predict the long-term change in depth distribution of soil temperature as well as to quantify temperature sensitivity of soil respiration along depth. The evaluated sensitivity of surface CO2 emission rate to atmospheric temperature showed hysteresis, implying the needs for more knowledge about temperature sensitivity of soil respiration evaluated in both warming and cooling processes for better understandings and predictions about terrestrial carbon cycling.

Logistic模型的改进及在油藏可采储量预测中的应用

为了更准确地预测油气藏未来的经济可采储量,依据油气藏随开发必然要经历产量递减和生产收支平衡的实际,利用Logistic模型中技术可采储量、产量与时间的相互关系,经推导和改进后,再结合当前经济技术条件下的废弃产油量,预测油气藏的有效生产时间及其经济可采储量。实践证实,改进后的Logistic模型预测结果更符合油气藏的生产实际,能为油气藏的储量管理提供可靠的依据。

含大规模风光电源电力系统随机生产模拟

从电源规划的角度,利用随机生产模拟对新能源接入系统发电成本进行评估。根据风电与光伏电源的自身电源特性及其与电网的相互关系,提出风电与光伏电源参与随机生产模拟的原则。根据所提原则对应提出风功率损失期望及弃风比率2个评价指标。并利用IEEE-RTS测试系统验证了所提原则及方法的有效性与可行性。

天然气开发中气藏废弃条件研究及应用

从经济学的角度出发,应用盈亏平衡分析,研究了天然气开发中气藏废弃产量计算方法,在此基础上,根据地层压力与产量的关系,得到了相应的废弃地层压力,经在实践中应用,取得了较好的开发效果和经济效益。

油田开发中后期可采储量标定方法

在油田开发中后期,部分油田或开发单元调整产液结构后,水驱特征曲线表现出“压头”、“上翘”现象,用水驱特征曲线计算的可采储量不能反映开发单元的实际开发状况。根据渗流力学原理,建立油田开发中后期开发单元采油速率与采出程度之间的关系式,利用该关系式可计算出油田开发单元的最终采收率及可采储量。应用分析表明,该方法计算的可采储量合理,较好地解决了在油田开发中后期水驱曲线变形给标定采收率带来的困难。

一种计算气藏废弃压力的方法——二项式产能方程法

废弃压力是准确计算气藏采收率和可采储量的基础和前提。二项式产能方程法评价气藏废弃压力能够反映出气藏原始压力、气藏埋深、储层非均质特征、以及不同废弃条件等多种因素对于废弃压力的影响,因此该方法评价结果较传统废弃压力评价方法如经验法、气藏埋深法等更可靠。针对二项式产能方程法在求解参数过程中存在的难点,对该方法进行了迭代改进,并编写了相应程序,提高了计算效率及精度。

超稠油油藏废弃产量界限的确定

针对杜229断块超稠油油藏开采效果逐渐变差的趋势,通过生产规律分析和推算,提出了合理的废弃产量界限,从而为该区块超稠油的合理开发提供了依据。

苏里格气田含水气藏废弃地层压力确定的新方法

苏里格气田是典型的致密砂岩气藏,储层不但致密,非均质性强,气井产量低,且多数产水,气藏采收率低。废弃地层压力是气藏采收率的关键影响因素之一,对于不产水气藏可以通过单相二项式产能方程结合经济极限产量综合确定,但对于产水气藏废弃地层压力的确定国内外研究不多。本文针对苏里格气田产水气藏,以最小携液速度下的产气量与产水时经济极限产气量相结合共同确定了废弃产量区间范围,应用质量守恒原理推导得出气水两相产能公式,最终求取含水气藏废弃地层压力的一种新方法,并对影响因素进行分析。本文利用VC编程采用多次迭代计算,提高了计算精度,为产水气藏废弃地层压力的求取及采收率的确定提供了一种新思路。

强非均质气藏废弃地层压力的确定

传统的废弃压力评价方法，如经验法、气藏埋深法等，只是考虑原始地层压力、气藏埋深对于气藏废弃地层压力的影响，没有考虑储层物性及其他相关因素的影响，计算结果往往具有偏差。本文提出采用二项式产能方程法、数值模拟法对气藏的废弃压力进行评价，评价结果能够反映出气藏平面非均质特征，并考虑到不同废弃条件对于废弃地层压力的影响，因此计算结果较为可靠。另外本文首次提出了二项式产能方程法的具体迭代求解过程，并编写了相应程序，提高了效率及精度。

储能电站对电网购电特性的影响研究

储能电站在电网中应用广泛,由于其能量搬迁作用,大规模储能电站对电网购电特性的影响很大。文中采用基于数学优化的生产模拟仿真程序,考虑了机组启停、水电跨周调节、抽蓄跨日调节、光热电站跨日调节,比较了储能电站对电网购电减少量、最大购电功率和新能源弃电的影响,研究了购电曲线对购电量的影响,确定外购电方式。并在确定购电方式后,分析储能电站对购电特性的影响。西北某实际电网的仿真计算结果表明,相比于直线购电方式,阶梯式购电方式可减少电网外购电量和新能源弃电率,但最大购电功率增加;在阶梯式购电基础上,建设储能电站,可进一步降低电网外购电量、新能源弃电率和最大购电功率,建议采用阶梯式购电方式并建设1200 MW储能电站。研究成果可为我国高比例新能源系统电网侧储能电站的建设提供参考。

Carbon Productivity Analysis to Address Global Climate Change

Developing low-carbon economy and enhancing carbon productivity are basic approaches to coordinating economic development and protecting global environment, which are also the major ways to address climate change under the framework of sustainable development. In this paper, the authors analyze the annual rate of carbon productivity growth, the differences of carbon productivity of different countries, and the factors for enhancing carbon productivity. Consequently, the authors clarify their viewpoint that the annual rate of carbon productivity growth can be used to weigh the efforts that a country takes to address climate change, and propose policies and suggestions on promoting carbon production.

提升局部区域新能源外送能力的储能容量优化配置方法

局部区域内的新能源大规模集中开发会造成严重的弃电问题,配置一定规模的储能装置可显著减少弃电。文中基于时序生产模拟软件和概率统计分析方法研究了考虑新能源发电不确定性和弃电率约束的局部断面储能容量配置问题。首先,介绍了主流的时序生产模拟软件的算法框架;基于该软件在考虑新能源出力的不确定性下获取局部区域断面的弃电曲线。然后,考虑弃电率限制,利用恒功率法确定储能的初始配置规模,再对断面弃电时长进行累积概率统计分析以得到储能最佳时长;进而对储能进行优化配置,得到满足弃电率约束的储能最佳配置规模。最后,针对中国西北某省实际电网进行了算例分析,并对储能配置规模与新能源装机占比和新能源利用率开展敏感性分析,验证了所提方法在求解方面的便捷性。