煤层气井煤粉成因、运移和防控研究进展

doi:10.13809/j.cnki.cn32-1825/te.2020.04.011

摘要/Abstract

摘要：

我国煤层气开发以高阶煤为主,高阶煤脆性较大,在钻井、压裂工程中以及排采过程中易破碎产生煤粉。生产过程中,煤粉被水流搬运从而参与流动。随着产水递减,储层中煤粉的沉降会导致流动通道的堵塞,使得煤储层的渗透率大幅度降低。当煤粉进入气井井筒后,井底的煤粉可能使泵吸入口堵塞,造成卡泵、埋泵等事故,使得气井停产修井。综述了煤层气生产过程中煤粉产生的机理、运移规律以及目前主要的控粉措施,分别论述了煤粉产生的力学模型、水动力学模型,在储层以及井筒中运移机制的研究进展,将煤粉的运移全过程总结为剥蚀产生、流化启动、悬浮运移以及沉降堵塞四个阶段。我国的煤田地质构造复杂,部分含煤盆地的后期改造作用强烈,破碎的煤体加剧了煤粉产出和运移问题,而煤层气井的控粉工艺多借鉴油藏防砂技术,尚未形成针对煤粉特点以及煤层气排采特征的煤层气井防粉控粉技术。

关键词: 煤层气, 煤粉, 运移机制, 控粉措施, 排采特征

Abstract:

CBM development in China focuses on the high-rank coal, which is brittle and, during drilling, fracturing and drainage, easily crushed into coal fine. During the production, coal fine flows owing to the water flashing effect. As the water production declines, the coal fine will sediment and block the flowing channels, leading to the great reduction of coal permeability. When the coal fine enter the wellbore, it may jam the pump, resulting in accidents in production such as pump stuck or buried pump, and leading to the stop of production for well repair. In order to solve this problems, the generation mechanism, migration rules and current major controlling approaches of coal fine are summarized. And then, the mechanics model, hydraulic model and migration model are investigated respectively. According to the former studies, the coal fine migration process can be summarized as four stages: denudation, detachment, suspension and sedimentation. However, the geology conditions of coal seam in China are extremely complex and the structure changes effect is dramatic on coal basins. These factors enhance the problems of production and migration. Nevertheless, the coal fine controlling approach method primarily learns from the sanding control technology in oil reservoir and is still undeveloped for the CBM reservoirs.

Key words: CBM（coalbed methane）, coal fine, flowing laws, power-controlling approach, generation and migration

中图分类号:

TE37

吴昊镪,彭小龙,朱苏阳,冯宁. 煤层气井煤粉成因、运移和防控研究进展[J]. 油气藏评价与开发, 2020, 10(4): 70-80.

WU Haoqiang,PENG Xiaolong,ZHU Suyang,FENG Ning. Research progress of coal fine formation, migration and control in CBM well[J]. Reservoir Evaluation and Development, 2020, 10(4): 70-80.

图/表 14

图1

图2

图3

表1

煤粉动力学分析的模型"

模型名称	表达式	变量含义
惯性力	$I = ρ s d 2 v a 18 μD$	控制悬颗粒特性的有关重要参数,颗粒概括为粒径（d）,m;孔隙介质颗粒的直径（D）,m; 颗粒密度（ρ_s）,g/cm³;黏度（μ）,mPa·s;对流速度（v_a）,m/s
球形Stokes速度	$v s = (ρ s - ρ) g d 2 18 μ$	g为重力加速度,m²/s;ρ为携带液的密度,g/cm³
离心力	$G c = R ω 2 (ρ s - ρ) d 2 18 μ v a$	离心力由外部加速度产生的,以角速度ω和半径R产生的
布朗扩散模型	$D = KT 3 π μd$	直径小于1 mm的小颗粒在液体介质中的布朗运动。T为绝对温度
扩散力	$P e = 3 π μD v a KT$	K=1.38×10^-23为玻尔兹曼常数
吸附力	$Fvw (s) = 1 (s - 2) 2 F n (s - 2 λ)$	作用在颗粒表面,其中London-Van der Waals力为引力,s为径向间隔距离除以颗粒半径
双电层斥力	$F R (s) = exp [- kd (s - 2)] 1 + exp [- kd (s - 2)]$	当微粒和流体吸附层内的离子具有同性的电荷时,产生斥力,k为Debye倒数双层厚度,m
剪切力	$τ = μ dv dr$	固相微粒附近的流体流过固相时对固体颗粒表面产生的剪应力

表1

图4

表2

图5

图6

图7

图8

图9

图10

表3

图11

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研究人员	研究时间	研究内容
HAN等	2015	将煤粉按产生过程和产生机理进行了系统分类,并进行了煤粉运移的岩心实验,用统计方法建立了煤粉流动模型
张芬娜等	2015	依据疏松砂岩出砂理论,对岩石在单相水流排采阶段中开展受力分析,研究了煤粉运移的启动条件
綦耀光等	2015	研究了煤粉沉降对煤储层渗流通道的影响,建立了煤粉沉积压裂缝物理模型和数学模型
徐鸿涛	2016	通过支撑剂沉降模型,描述煤粉在支撑剂孔隙中的沉降规律
王铭伟	2016	基于煤粉在割理中的流动实验,初步建立了描述煤粉流动的数学模型,并通过等效数值模拟研究
马飞英等	2016	为了对适度出粉排采策略进行探索,建立了单相水流阶段煤储层裂缝中沉积煤粉启动的力学模型
IGOR & NICOLAS	2017	研究了煤储层渗透率的应力敏感与煤粉运移对产生动态的影响
ZHU等	2017	建立煤粉流动的数学模型,并通过等效数值模拟研究
皇凡生等	2017	推导了煤粉的启动压力梯度公式,研究了煤储层中煤粉稳定剂注入对煤粉的防控措施
GUO & PHUNG	2018	实验研究了单相流动条件下,煤粉在岩心尺度上的运移规律

阶段划分名称	阶段划分依据		特征阶段	适用范围	优点	缺点
阶段划分名称	主要依据	辅助依据	特征阶段	适用范围	优点	缺点
三段划分法	产气量	产水量井底压力	定量产水段负递减段产气递减段	中高渗煤层	简单明了,表明了中高渗煤层的主要排采特征	因素较少,指导性较差
四段划分法	产水量井口套压井底流压产气量	解吸压力废弃压力	排水段憋压控压段高产稳产段衰竭段	中低渗煤层	生产特征明显,同时具有压力和产量特征	划分标准不统一,压力和产量同时为划分依据, 命名不统一
六段划分法	产气量	产水量井底压力	未见气段见气段产气上升段气量稳定段产气递减段废弃段	低渗透煤层	划分标准简单, 能直接反映生产过程中的产气产水状况	划分阶段稍复杂