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高校地质学报 ›› 2020, Vol. 26 ›› Issue (5): 559-568.DOI: 10.16108/j.issn1006-7493.2019083

• 能源地质学 • 上一篇    下一篇

基于“定体积法”的大佛寺井田煤储层稳产阶段动态含气量反演

刘巧妮1,刘钰辉1,2   

  1. 1. 中煤科工集团 西安研究院有限公司,西安 710077;
    2. 西安理工大学 水利水电学院,西安 710048
  • 出版日期:2020-10-20 发布日期:2020-10-28

Inversion of the Dynamic Gas Content of the Coal Reservoir during Stable Production in the Dafosi Area Based on “Constant Volume Method”

LIU Qiaoni 1,LIU Yuhui 1,2   

  1. 1. Xi’an Research Institute, China Coal Technology & Engineering Group Corp., Xi’an 710077, China;
    2. Xi’an University of Technology,Xi’an 710048, China
  • Online:2020-10-20 Published:2020-10-28

摘要: 含气量是影响煤层气井生产的关键参数,但是,多数煤层气井无法直接获得目标煤层含气量,且解吸法测定的低阶煤储层含气量误差较大。文章以大佛寺井田煤层含气量动态变化特征为研究目标,结合煤层气井排采数据对煤储层参数动态的同步反馈,采用“定体积法”分析煤层气井排采数据,进行4#煤储层实时含气量的动态反演。结果表明:(1)设定多个原始含气量,实时含气量随时间变化呈线性递减关系,且下降趋势一致,皆能得到实时含气量变化线性斜率相同的结果:产气量与含气量消耗同步,且与生产时间间隔无关。(2)分析1 d、3 d、5 d的不同时间步长,设定原始含气量分别为2 m3/t、3 m3/t、4 m3/t、5 m3/t、6 m3/t、8 m3/t时,煤储层实时含气量变化关系高度一致,认为煤层气井遵循“定体积”产气规律,即不存在压降漏斗的形成与扩展。(3)连续排采阶段,实时含气量与排采时间呈线性降低关系,排采间断前后两个阶段煤储层实时含气量线性降低速率不同:为-0.00546和 -0.00435;第二阶段较第一阶段实时含气量变化斜率减小,是因为排采过程产生煤粉,堵塞阻碍块煤的解吸作用,造成储层伤害,能够解吸的煤层体积缩小。

关键词: 煤层气, 排采, 定体积法, 含气量, 反演

Abstract: The gas content of coal reservoir is one of the key factors affecting gas production, which cannot be achieved directly for most gas wells, and the gas content of low-rank coal measured by desorption method is not accurate. The purpose of this study is to determine the dynamic variation of gas content of the coal reservoir in the Dafosi coal field by synchronizing feedback of coalbed methane (CBM) well drainage and production data to coal reservoir parameter dynamics and by studying the real-time gas content inversion through “constant volume method” using the production data of CBM wells. The results show that (1) for multiple original gas contents, qA decreases linearly with time and the descending trends are the same. Also, the real-time gas content changes with the same linear slope: gas production and gas consumption are synchronized, regardless of the production time interval. (2) Analyzing different time steps of 1 d, 3 d, and 5 d, and setting original gas content of 2 m3/t, 3 m3/t, 4 m3/t, 5 m3/t, 6 m3/t, and 8 m3/t respectively, the real-time gas content change relationship of coal reservoir is highly consistent. It is considered that CBM wells follow the law of “constant volume” gas production, that is, there is no formation and expansion of pressure drop funnel.(3)In the continuous drainage stage, the real-time gas content decreases linearly with the drainage time. The linear reduction rates of real-time gas content in coal reservoirs are different before and after the interruption of drainage and production: 0.00546 and -0.00435, respectively; the slope of real-time gas content change in the second stage is smaller than that in the first stage, which is interpreted to result from coal powder that was produced in the process of drainage and mining, blocking the desorption of lump coal, causing reservoir damage and reducing the volume of coal seam to be desorbed.

Key words: coalbed methane, production, constant volume, gas content, inversion

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