基于流态物理模拟实验的煤粉产出机理研究

In the process of CBM drainage and production, the pulverized coal stuck in the pore of the cracks, gradually decrease conductivity of fracturing, so that the premature decay phenomenon of CBM productivity; pulverized coal deposition in the well, leading to the buried pump and stuck pump, thus the continuity of flow pattern with gas, water and coal is destructed, and thus influence the potential of gas production; It has become the bottleneck of the CBM scale development that the dynamic output of the pulverized coal. The key of high-yield and stable -yield coal bed methane wells is to reasonably control output of pulverized coal. Based on fully collecting and analysis the coal quality, log interpretation, fracturing and completion reports, drainage daily data of selected typical of the study area, focus on physical simulation of pulverized coal flow state output, and as the secondary research methods with analysis of experiments with pulverized coal, coal and rock properties, and analysis of experiments with pulverized coal, coal and rock properties is as the secondary research methods, the project is planned to summarize the law of the pulverized coal output from the macro and micro perspective, to condense out scientific the output mechanism and influence factors of the pulverized coal under different drainage and production conditions. The results have important guiding significance, to elucidate the mechanism of pulverized coal output, to develop reasonable and effective engineering control measures of pulverized coal according to different coal reservoir characteristics and different drainag

煤层气排采过程中，煤粉滞留在裂缝中的孔道内，逐渐降低压裂形成的裂缝导流能力，使煤层气井产能过早出现衰减现象；煤粉在井内沉积，导致埋泵和卡泵，从而破坏气、水、煤粉流态的连续性，进而影响产气潜力；煤粉的动态产出已成为煤层气规模开发的瓶颈，合理地控制煤粉产出成为煤层气井高产、稳产的关键。本项目拟在充分收集和分析选定典型研究区的煤质、测井解释、压裂完井报告、排采日报等资料的基础上，以煤粉流态产出物理模拟实验研究为重点，以煤粉、煤岩物性分析实验为辅助研究方式，力求从宏观和微观角度总结煤粉产出的规律，科学凝练出不同排采条件下煤粉的产出机理及其影响因素。研究结果对阐明煤粉产出机理，进而针对不同煤储层特征、在不同排采过程中制定合理、有效的煤粉工程管控措施，实现煤层气井高产、稳产具有重要的指导意义。

煤层气排采过程中，煤粉滞留在裂缝中的孔道内，逐渐降低压裂形成的裂缝导流能力，使煤层气井产能过早出现衰减现象；煤粉在井内沉积，导致埋泵和卡泵，从而破坏气、水、煤粉流态的连续性，进而影响产气潜力；煤粉的动态产出已成为煤层气规模开发的瓶颈。为研究煤层气井排采过程中煤粉的产出机理及其影响因素及不同煤岩组分对煤粉产出的差异影响，本基金开展了单相流驱替状态下煤粉产出物理模拟实验。通过改变单相流驱替流速及煤砖样品上、下围压的大小，分析不同实验条件下煤粉产出量、煤粉粒度分布特征以及裂隙导流系统的渗透率变化等参数，查明了不同煤岩组分状态下的煤粉的动态产出规律，揭示了围压、流压、流速、流量等对煤粉产出的影响，归纳煤粉的动态产出规律。实验结果表明：（1）在围压稳定的实验条件下，煤粉的产出具有一定的启动运移速率；煤粉的产出量与驱替液流速呈正相关、与围压呈负相关；煤粉在裂隙系统中的存在与运移会对其渗透率产生显著的影响；间断后重启单相流驱替作用会使煤粉产出量瞬间剧增。（2）随流速及围压的增加，煤粉产出均有增大的趋势；粘土含量越高的煤岩，煤粉的产出量越大，且产出煤粉受驱替流速变化的影响越大；镜质组含量越高的煤岩,围压的增大会使煤粉的产出速率减小，且产出煤粉受围压变化的影响越大；围压不变，随驱替流速增大，煤岩渗透率均有增大的趋势，且流速越大，不同煤岩组分的渗透率变化趋势越接近；煤岩中粘土矿物可显著影响渗透率的变化，粘土矿物含量越高，渗透率则迅速提升；流速保持不变，随着围压的增大，煤岩渗透率均有降低的趋势；同时较少的粘土矿物含量无法有效地聚合分散的煤粉颗粒，表现为渗透率的持续降低。根据模拟实验结果可以认为,优化煤层气井的排采制度、控制井底流压降压速率的变化、稳定控制排水强度，将会有效地控制煤粉的产出量。