西山煤田古交矿区煤层气富集规律及产能主控因素研究

发布时间：2018-05-17 12:29

本文选题：古交矿区 + 煤储层　；参考：《太原理工大学》2017年博士论文

【摘要】：本文收集了西山煤田古交矿区煤矿采掘工程地质及煤层气井相关资料;开展了矿区野外地质填图及矿井煤层剖面地质编录工作;采集了矿区2#、8#煤层新鲜样品17组,并进行了煤岩组分、镜质体反射率、甲烷等温吸附、低温氮比表面积、常规孔渗、变围压孔渗及核磁共振等实验分析;采集了煤层气井产出水样品30组,进行了水化学检测。综合各类地质资料及实验结果,分析了古交矿区2#、8#煤层地质特征;结合煤层含气量分布规律,对古交矿区煤层气分布模式进行了系统研究,揭示了不同分布模式下煤层气的富集规律;在煤层气地质特征研究及分布模式划分基础上,结合工程措施及排采制度,定量分析了古交矿区不同区块内产气量主控因素。论文研究获得的主要成果和认识如下:(1)将古交矿区划分为平缓单斜浅埋、平缓单斜深埋、陡峭单斜、复杂褶皱4种煤层气分布模式。复杂褶皱模式和陡峭单斜模式下煤层含气性差、含气饱和度低,平缓单斜浅埋及平缓单斜深埋模式下煤层含气性好。平缓单斜浅埋模式下煤层气富集条件是埋深大、保存条件好;平缓单斜深埋模式下埋深小、水动力弱有利于煤层气富集。(2)基于古交矿区煤层气井产能特征,结合无因次产气率及煤层气等温吸附/解吸过程,揭示矿区内煤层气井达到稳产时对应无因次产气率为0.65。计算了古交矿区煤层气井稳产气量,并对煤层气井产能进行了分级:高产井产气量大于500m3/d,大于1000m3/d为特高产井;中产井产气量300~500m3/d;低产井产气量小于300m3/d,产气量等于0为干井。(3)古交矿区内煤级变化大,随煤岩变质程度升高,抗压强度和渗透率稳定性增强,渗透率损伤率逐渐减小。气煤、肥煤及焦煤煤质相对较软,压裂过程中易发生变形,并产生大量煤粉堵塞裂隙,阻断流体渗流通道。针对这类煤储层,在煤层气开发过程中应当慎重采用直井水力压裂开发方式。(4)气井排采过程中,随着储层压力下降,大孔、裂隙中自由气和溶解气首先渗流至井筒,小孔中吸附气逐渐开始解吸,当储层压力下降一定幅度后,微孔中吸附气才开始缓慢解吸。电阻率测井、水力压裂关键压力数据是评估煤储层压裂改造前、后渗透性的重要参数。建立了电阻率对原始储层渗透率的评价模型。探索了破停压力差、停降压力差评价压裂改造效果的可行性。(5)古交矿区内:平缓单斜浅埋模式下,煤储层原始渗透性、压裂改造效果对产气量影响最显著;平缓单斜深埋模式下,产气量主要受到资源量的影响,渗透率的影响相对较小;陡峭单斜模式下,煤层气井无法有效排水,区块内煤层气井产水量均为0,整体产气效果差,不具有高产井;复杂褶皱模式下,煤层气井产能主要受控于排采因素,排水效果好、生产压差小最有利于煤层气井高产。
[Abstract]:This paper has collected the relevant data of mining engineering geology and coalbed methane wells in Gujiao mining area of Xishan coalfield, carried out the field geological mapping and geological cataloguing of coal seam section in mining area, collected 17 groups of fresh samples of 2 #n8# coal seam in mining area, The composition of coal and rock, vitrinite reflectance, isothermal adsorption of methane, specific surface area of nitrogen at low temperature, conventional porosity and permeability, perturbed pore permeability and nuclear magnetic resonance (NMR) were analyzed, and 30 groups of water samples from coalbed methane wells were collected and tested by hydrochemistry. Based on all kinds of geological data and experimental results, the geological characteristics of coal seam No. 2#y8# in Gujiao mining area are analyzed, and the distribution pattern of coalbed methane in Gujiao mining area is systematically studied in combination with the distribution law of gas content in coal seam. The enrichment law of coalbed methane under different distribution modes is revealed, and the main controlling factors of gas production in different blocks of Gujiao mining area are quantitatively analyzed on the basis of the study of geological characteristics of coalbed methane and the division of distribution model, combined with engineering measures and drainage system. The main achievements and understandings of this paper are as follows: (1) the Gujiao mining area is divided into four coalbed methane distribution models: flat monoclinal shallow burying, gentle single oblique deep burying, steep monoclinal and complex fold. Under the complicated fold model and steep monoclinal mode, the gas content of coal seam is poor, the gas saturation is low, and the gas content of coal seam is good under the flat monoclinal shallow burying mode and the gentle monoclinal deep burying mode. The enrichment conditions of CBM in flat monoclinal shallow burial mode are large buried depth and good preservation condition, and the buried depth is small in flat monoclinic deep buried mode, and the weak hydrodynamic force is favorable to coalbed methane enrichment. 2) based on the productivity characteristics of coalbed methane wells in Gujiao mining area, Combined with dimensionless gas production rate and isothermal adsorption / desorption process of coalbed gas, it is revealed that the corresponding dimensionless gas production rate of coalbed gas wells in mining area is 0.65 when they reach stable production. The steady gas production of coalbed gas wells in Gujiao mining area is calculated, and the productivity of coalbed gas wells is classified as follows: the gas production of high production wells is more than 500m3 / d, which is greater than that of 1000m3/d wells; The gas production of middle production wells is 300 ~ 500m3 / d; the gas production of low production wells is less than 300m3 / d, and the gas production is equal to 0) the coal rank in Gujiao mining area changes greatly, with the increase of metamorphic degree of coal and rock, the compressive strength and permeability stability increase, and the permeability damage rate decreases gradually. The coal quality of gas coal, fat coal and coking coal is relatively soft, and it is easy to deform during fracturing, and a large amount of pulverized coal is produced to block the fissure and block the fluid seepage channel. In view of this kind of coal reservoir, in the process of coalbed methane development, the hydraulic fracturing development mode of vertical well. Y4) should be carefully adopted. In the process of discharging and producing gas wells, with the decrease of reservoir pressure, the free gas and dissolved gas in the big pore and fracture flow first to the wellbore. The adsorbed gas begins to desorb gradually, and when the reservoir pressure decreases by a certain extent, the adsorption gas in the micropore begins to desorb slowly. Resistivity logging and key pressure data of hydraulic fracturing are important parameters for evaluating permeability of coal reservoir before and after fracturing. The evaluation model of resistivity to original reservoir permeability is established. In Gujiao mining area, the original permeability of coal reservoir and the effect of fracturing modification on gas production are most significant under the flat and single oblique shallow burying mode. The gas production is mainly affected by the amount of resources, and the influence of permeability is relatively small under the mode of flat and single oblique deep burying, and the coalbed methane well can not be effectively drained under the steep monoclinic mode, and the water production of the coalbed gas well in the block is all 0, and the overall gas production effect is poor. Under the complex fold model, the productivity of coalbed gas wells is mainly controlled by the factors of drainage, the drainage effect is good, and the production pressure difference is the most favorable to the high production of coalbed gas wells.
【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TE37;P618.13

【参考文献】