基于核磁共振的煤层气产出过程气水动态变化规律模拟

发布时间：2018-03-16 13:50

本文选题：核磁共振　切入点：驱替　出处：《中国矿业大学》2016年硕士论文　论文类型：学位论文

【摘要】：本文以沁水盆地无烟煤为研究对象,探讨了2D NMR中T1-T2技术在区分甲烷和水信号方面的可行性及利用型煤替代原煤进行煤层气产出过程甲烷和水状态研究的可行性。通过观测CO2驱水过程中T2谱图变化,分析了CO2对煤储层中水的状态的影响;通过观测重水驱甲烷过程中T2谱图变化,分析了煤层气产出过程中水和驱替压力对甲烷产出的影响。研究结果如下:2D NMR和型煤驱替实验表明,甲烷和水的T1和T2比值十分接近,试图通过二维谱T1-T2区分煤体中甲烷和水的信号比较困难;用型煤代替原煤时,所用粘合剂要求在整个实验过程中均无核磁共振信号。不同渗透率煤样的CO2驱水实验表明,对低渗储层,煤层气在储层中的运移非常困难;开采深部煤层气时,储层的可改造性尤为重要;CO2能够改变煤的润湿性,使煤储层中吸附水逐渐向自由水转变。干燥煤样和含水煤样吸附解吸实验表明,甲烷的吸附是由大孔隙向小孔隙逐渐吸附,且在煤表面甲烷的吸附解吸随时间的变化符合对数关系。整个吸附过程可分为三个阶段,前两个阶段为线性变化阶段,第三个阶段为对数变化阶段。其中,第一个线性阶段,吸附速率非常大,说明解吸初期,解吸速率也非常高。同时发现,煤柱中吸附甲烷量在一定范围内时,其吸附速率与压力相关性不大。煤柱中的水不但阻碍甲烷的运移,还降低了甲烷在煤表面的吸附速率。一方面是由于煤表面对水的吸附能力强于甲烷;另一方面是一部分孔隙可能被水填满;同时,由于孔隙的不规则性,水分子会阻塞部分孔隙,导致甲烷分子无法进入这部分孔隙。煤柱中水对甲烷运移速度的影响,是由于煤表面、水分子和甲烷分子之间的作用力以及水对运移通道的堵塞作用造成的。煤柱中的水降低了甲烷的解吸速率,但对其整体规律影响不大,说明水对煤储层甲烷解吸影响的根本原因是水对煤储层吸附甲烷的影响。重水驱替甲烷实验表明,驱替压力对甲烷的产出起双重作用,既有促进作用,又有阻碍甲烷解吸的作用。在煤层气持续产出过程中,储层含水量对煤层气解吸的影响已经不是主要因素,关键是井底压差的控制。实验模拟发现,大宁区块煤层气井的井底压差应控制在0.5-1.5 MPa之间。同时,在注气开采中,驱替压力的控制非常重要。
[Abstract]:Taking Qinshui Basin anthracite as the research object, discusses the technology of T1-T2 2D NMR in the process of coal-bed methane and water output of the state of the feasibility in distinguishing the feasibility of methane and water signals and the utilization of coal instead of raw coal by observation of CO2 flooding diagram change spectrum of T2 in the process of water, analyzes the influence of CO2 on coal reservoir the state of water; by observing the changes of T2 spectrum diagram of heavy water flooding methane process, analyzes the process of water production of coalbed gas and the displacement pressure of methane output. The results are as follows: 2D and NMR coal displacement experiment shows that methane and water T1 and the ratio of T2 is very close, trying to distinguish the signals of methane and water the coal in the two-dimensional spectrum of T1-T2 is difficult; instead of coal briquette, the adhesive required during the whole experiment. There were no NMR signals of different permeability of coal sample CO2 water displacement experiment showed that the low Permeability reservoir, coalbed gas migration in the reservoir is very difficult; deep coal mining gas reservoir, the transformation can be particularly important; CO2 can change the wettability of coal, the adsorption water gradually transformed into free water in the coal reservoir. Dry coal and water coal adsorption desorption experiments showed that adsorption of methane is gradually adsorbed by large pores to small pore, and the adsorption and desorption of methane in coal surface changes over time in line with the logarithmic relationship. The adsorption process can be divided into three stages, the first two stages are linear stages, third stages for the logarithmic change stage. In the first stage, linear. The adsorption rate is very large, that the initial desorption, desorption rate is very high. At the same time, the coal pillar in the adsorption amount of methane in a certain range, the adsorption rate and pressure are not relevant. Migration of coal pillar in the water will not only hinder the methane, reducing methane in coal The adsorption rate of the surface. On the one hand is due to the coal surface adsorption ability to face strong water to methane; on the other hand is a part of the pore may be filled with water; at the same time, due to the irregular pore, the water molecules will lead to pore blocking part, methane molecules can not enter the pores. The influence of coal on water column methane migration speed, due to the coal surface, caused by blockage of interaction between water molecules and methane molecule force and water on the migration channel. The coal pillar water reduces methane desorption rate, but it has little effect on the overall pattern, the root cause of water on coal reservoir methane desorption affects the effect of water on coal the reservoir of methane adsorption. Heavy water flooding experiment indicate that the displacement pressure of methane, methane output plays a dual role, both promote and hinder the methane desorption effect. In the continuous output of coalbed gas in the process of reservoir water The influence of quantity on the desorption of coal-bed gas is not the main factor. The key is the control of bottom hole pressure difference. Experimental simulation shows that the bottom hole pressure difference of CBM well in Daning block should be controlled between 0.5-1.5 MPa. Meanwhile, the control of displacement pressure in gas injection mining is very important.

【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE37

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