【作者】 乔磊；

【导师】 焦养泉； 王小明；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2013， 博士

【摘要】 新安煤矿属于高瓦斯高突矿井,主采煤层二1煤主要为构造煤,经过近30多年的煤矿开采,浅部开采任务已基本完成,近年来,随着开采深度的增加和新区的开发,矿井瓦斯涌出量急剧上升,储层特征各向异性更加明显,对瓦斯地质资料的要求越来越严格。以往提供的瓦斯资料缺乏对影响瓦斯涌出量相关因素的综合分析和研究,尤其缺乏针对储层特征参数所作出的瓦斯地质分析,难免造成新采区设计工作的盲目性,迫切需要采用新思路和新方法并从储层特征的非均质性出发,对新安煤矿二水平的瓦斯涌出量情况进行精细的研究。论文将以新安矿二1煤层为研究对象,在资料的收集、整理和对已有成果消化吸收的基础上,综合钻井、井下观察、测试数据,结合瓦斯地质因素的平面分布特征,查明瓦斯地质因素(埋深、煤厚、20米砂岩比、40米砂岩比、大占砂岩厚度、灰分产率、水分、挥发份、全硫、煤岩显微组份、镜质组射率、断层落差、构造复杂程度等)对储层特征参数(瓦斯压力、孔隙裂隙、等温吸附、瓦斯含量、比表面积)的控制作用,结合数量化理论Ⅰ数学建模工具,对储层特征参数未采区定量化,重点重建了基于储层特征参数的瓦斯涌出量多变量数学模型,结合瓦斯地质理论,分析了储层特征对瓦斯涌出量的控制作用。论文首先选取合适的控制因素指标,综合判别新安煤矿二1煤储层特征的主要控制因素,定性定量分析埋深、煤厚、20米砂岩比、40米砂岩比、大占砂岩厚度、灰分产率、水分、挥发份、全硫、煤岩显微组份、镜质组射率、断层落差、构造复杂程度等对煤储层特征参数的影响,建立各地质因素与煤储层特征参数的对应关系,探讨各地质因素对储层特征的控制作用；研究已采区宏观煤岩类型,观察其裂隙特征,研究煤的微观孔隙裂隙特征,包括孔隙大小及其连通性,对裂隙研究包括裂隙长度、裂口宽度、裂隙类型及其发育程度等；分析煤的等温吸附特征、煤的储层渗透率特征、煤储层的瓦斯含量特征、煤储层的比表面积特征和煤储层瓦斯压力特征；分析煤储层特征对瓦斯的吸附能力以及解吸特性等；对己采区划分统计单元,选择己采区变量并取值,运用瓦斯地质理论和方法,分析已采区孔隙裂隙、等温吸附、渗透性、瓦斯含量、比表面积、瓦斯压力与埋深、煤厚、20米砂岩比、40米砂岩比、大占砂岩厚度、灰分产率、水分、挥发份、全硫、煤岩显微组份、镜质组射率、断层落差、构造复杂程度等等控制参数关系,筛选出主导控制参数,建立多元分析数学地质模型,对未采区煤储层特征参数定量化；分析已采区瓦斯涌出量特征,对已采区统计单元储层特征参数取值,建立已采区统计单元储层特征参数与瓦斯涌出量定量函数表达式；利用未采区煤储层特征的量化值,预测未采区瓦斯涌出量,构建基于储层特征参数的深部煤瓦斯涌出量预测模型,分析未采区储层特征对瓦斯涌出量的控制作用。取得的主要认识与结论如下：1、二1煤坚固性系数值都很低,在0.17-0.22之间,平均为0.19,是典型的构造软煤,是脆性剪裂变形的结果,碎粒煤、糜棱煤全面发育,严重破坏的煤岩可能以小颗粒或者粉末的形式随瓦斯运移,堵塞运移通道,从而降低了储层渗透性；2、二1煤孔隙十分发育,以变质孔偏多,原生孔多为丝质体、半丝质体空腔,部分孔隙被矿物充填,裂隙以构造裂隙为主,是瓦斯大量赋存的物质基础；比表面积测试结果显示,该区孔隙形态既有封闭型孔,也有开放型孔,封闭型孔居多。3、储层等温吸附常数a、b值均偏大,储层煤岩对瓦斯具有较强的吸附能力,当瓦斯压力由5Mpa降到1Mpa时,解吸瓦斯量较少,表明瓦斯总体解吸比较困难,当瓦斯压力小于1Mpa时,降压瓦斯解吸速率突然大增,成为瓦斯突出或煤与瓦斯突出的隐患,应成为瓦斯涌出量预测的重点区。4、储层平均渗透率为0.42mD,其中15061工作面煤层渗透率最大,为0.57mD,12201工作面煤层渗透率最低,仅为0.29mD。5、煤比表面积与断层落差、埋深和构造复杂程度成正相关；与Ro、镜质组含量、灰分产率、水分含量、惰质组含量成负相关；镜质组含量、埋深、水分含量、构造复杂程度的t统计量大于0.01显著性水平下的t临界值2.660；Ro、灰分产率、惰质组含量、断层落差的t统计量略小于0.1显著性水平下的t临界值1.671；t统计量检验说明镜质组含量、埋深、水分含量和构造复杂程度4个自变量对比表面积影响大,Ro、灰分产率、惰质组含量和断层落差4个自变量对比表面积影响相对较小。全区比表面积整体由矿区东北向西南呈现增加、减小,次增加的趋势,已采区高比表面积区域主要位于13采区和16采区,比表面积值大于0.8m2/g,低值区位于12采区,低于0.4m飞。6、等温吸附常数VL与Ro、比表面积、镜质组含量、断层落差、埋深、惰质组含量和构造复杂程度成正相关；与灰分产率、水分含量成负相关,埋深的t统计量大于0.01显著性水平下的t临界值2.660；镜质组含量、水分含量的t统计量介于0.1显著性水平下的t临界值1.671和0.01显著性水平下的t临界值2.660之间；Ro、比表面积、灰分产率、断层落差、惰质组含量、构造复杂程度的t统计量小于0.1显著性水平下的t临界值1.671,其中Ro、惰质组含量和构造复杂程度的t统计量略小于t临界值；t统计量检验说明埋深、镜质组含量、水分含量3个自变量对等温吸附常数VL影响大,Ro、比表面积、灰分产率、断层落差、惰质组含量、构造复杂程度6个自变量对等温吸附常数VL影响相对较小。全区等温吸附常数VL分布具有非均质性,变化幅度大,高值可达到35m3/t,低值则低于23m3/t,已采区11采区大部分区域等温吸附常数VL值高,大于32m3/t,其它采区VL值则分布不均。7、瓦斯含量与煤厚、瓦斯压力、镜质组含量、埋深、等温吸附常数VL、水分含量、惰质组含量成正相关；与20m砂岩比、40m砂岩比、比表面积、断层落差、灰分产率、Ro、大占砂岩厚度、构造复杂程度挥发分产率成负相关,瓦斯压力、比表面积、大占砂岩厚度的t统计量大于0.01显著性水平下的t临界值2.660；20m砂岩比、Ro、镜质组含量、水分含量和等温吸附常数VL的t统计量介于0.1显著性水平下的t临界值1.671和0.01显著性水平下的t临界值2.660之间；40m砂岩比、断层落差、煤厚、灰分产率、埋深、惰质组含量和构造复杂程度的t统计量小于0.1显著性水平下的t临界值1.671；t统计量检验说明瓦斯压力、比表面积、大占砂岩厚度、20m砂岩比、Ro、镜质组含量、水分含量和等温吸附常数VL8个自变量对瓦斯含量影响大,40m砂岩比、断层落差、煤厚、灰分产率、埋深、惰质组含量和构造复杂程度7个自变量对瓦斯含量影响相对较小。全区瓦斯含量值变化范围较大,可由3m3/t增加至16m3/t,瓦斯含量整体趋势由西北向东南逐渐增加,增加梯度大,瓦斯含量高值区出现在未采区的西南部,相对低值区主要位于未采区东北部大部分区域及中部部分区域,瓦斯含量小于10m3/t。8、瓦斯压力与煤厚、比表面积、瓦斯含量、埋深、大占砂岩厚度和构造复杂程度成正相关；与断层落差成负相关。埋深、大占砂岩厚度、比表面积的t统计量大于0.01显著性水平下的t临界值2.660;煤厚、瓦斯含量、构造复杂程度的t统计量介于0.1显著性水平下的t临界值1.671和0.01显著性水平下的t临界值2.660之间；断层落差的t统计量小于0.1显著性水平下的t临界值1.671；t统计量检验说明煤厚、比表面积、瓦斯含量、埋深、大占砂岩厚度和构造复杂程度6个自变量对瓦斯压力影响大,自变量断层落差对瓦斯压力影响相对较小。全区瓦斯压力整体由矿区西北部到东南部呈现先减小后增大的趋势,大致呈条带状,矿区东南部瓦斯压力高值区呈团块状,己采区高瓦斯压力区域主要位于14采区和16采区,瓦斯压力超过0.6MPa。9、瓦斯涌出量与瓦斯压力、瓦斯含量成正相关；与比表面积、等温吸附常数VL成负相关。瓦斯压力的t统计量大于0.01显著性水平下的t临界值2.660;瓦斯含量、比表面积的t统计量介于0.1显著性水平下的t临界值1.671和0.01显著性水平下的t临界值2.660之间；等温吸附常数VL的t统计量小于0.1显著性水平下的t临界值1.671；t统计量检验说明瓦斯压力、瓦斯含量、比表面积3个自变量对瓦斯涌出量影响大,等温吸附常数VL对瓦斯涌出量影响相对较小。矿区瓦斯涌出量整体呈现由东北到西南增加的趋势,局部区域分布具有非均质性。已采区高瓦斯涌出量主要位于12采、14采区和16采区,其它采区较小10、瓦斯涌出量主要受瓦斯压力的控制,瓦斯压力在本研究区内受埋深、大占砂岩厚度主导因素的控制,由此可以得出,在矿区内埋深对瓦斯涌出量起关键控制作用；该矿区构造不发育,瓦斯保存条件好,煤岩破碎,瓦斯渗流通道缺失,大占砂岩厚度在研究区没有起到逸散介质的作用,其厚度大小只起到增大瓦斯压力的作用。该矿区瓦斯涌出量与比表面积和最大吸附常数VL两参数呈负相关,但相关系数小,说明瓦斯压力和瓦斯含量影响了比表面积和最大吸附常数VL在该矿区对瓦斯涌出量的作用,因此,未采区开采二水平时,矿井瓦斯防治工作应重点放在分析瓦斯压力和瓦斯含量两个参数的特征及规律,未采区瓦斯防治指导方针应该从分析瓦斯压力着手,搞清未采区煤层的赋存情况。由于该区小构造主要发育在己采区的采掘工作面内,并不能说明未采区没有断层,只是未揭露,将来的瓦斯防治工作要做好提前探测小断层,分析其对瓦斯压力的控制作用,进一步指导瓦斯涌出量的预测工作。11、矿区张性小断层发育,使得煤大中孔增加,小微孔变化不大,游离气增加,吸附气减小,游离气体变化会影响瓦斯涌出量变化；另外,小断层可使次生孔隙增多,可使原有残留孔隙扩大,都将会引起瓦斯涌出量变大；小构造使煤的破坏程度变严重,连通性变差,瓦斯被封堵,当煤矿开采时,会引起瓦斯涌出量变大。12、矿区开放性小断层处应力释放,增大有效裂隙,瓦斯运移形成异地高瓦斯聚积区,此类断裂较远处瓦斯涌出量异常区；矿区小构造使煤显微组分混杂,渗透性变差,引起瓦斯涌出量的异常；矿区顶底板起伏,厚度变化非常大,厚煤带处裂隙网络连通性差,厚煤带易发生瓦斯涌出量的异常；开采过程应力集中带,裂隙受压闭合,渗透力降低,瓦斯涌出量变大；在卸压带内,裂隙张开及新裂隙的形成,渗透率提高,瓦斯涌出量变小。13、瓦斯含量越高,煤中吸附瓦斯多,含气饱和度高,瓦斯易解吸,瓦斯涌出量越高。新安煤矿二1煤层受走滑断裂控制,煤体破坏严重,储层渗透性降低,煤的吸附能力增加,沿着滑动构造形成糜棱煤带,有效地阻止了瓦斯的扩散,导致瓦斯涌出量变大；新安煤矿顶底板起伏引起的厚煤带更易生成裂隙,甲烷能得到充分的吸附和解吸,厚煤层处易出瓦斯涌出量异常。14、瓦斯的运移首先以扩散为主,扩散的主要动力是浓度差,浓度差主要由含气量决定,瓦斯含量越小,煤层厚度越大的地方,瓦斯向顶底板运移的路径越长,阻力越大,越有利于煤层瓦斯的富集,容易导致瓦斯涌出量的异常。15、矿区煤厚变化大,由厚变薄时,瓦斯压力减小,水平地应力增大,瓦斯涌出量异常；由薄变厚时,地应力水平分量指向巷道里端,瓦斯压力增大,瓦斯涌出量变大；矿区张性断层使孔隙压力减小,游离气体易进入此处,瓦斯压力变大,原裂隙扩展,与邻近岩层连通,气体不断移出,可在一定程度上使瓦斯涌出量变小；逆断层使煤层始终保持较高瓦斯压力,使有效应力减小,煤抵抗破坏能力增大,可在一定程度上使瓦斯涌出量变小。更多还原

【Abstract】 After nearly30years’ mining, seam in shallower areas(belonging to the first level), within Xin’an Coalmine, which is of high gas/coal-outburst mine for the principle coalseam-Ⅱ1Coal is tectonic coal, has been mined out. During mining down, gas emission increases dramatically, while the high heterogeneity in reservoir properties makes it more difficult to design new panel reasonably. However, available geology reports lack comprehensive analysis or researches on factors that control gas emission. Accordingly, it is more important to characterize and predict gas emission in deeper areas (belonging to the second level) on the base of reservoir heterogeneity for reasonable design.This thesis studied the Ⅱ1Coal in Xin’an mine, clarified relationship between gas-geology parameters(i.e. coal seam depth (D), seam thickness (T),20m-sandstone ratio (20m-SR),40m-sandstone ratio (40m-SR), ash content (A), moisture content (M), total sulfur (S) and tectonic indicator (TI) et al.) and reservoir parameters (including gas pressure (GP), ⅤL, gas content (GC) and fracture in seam), based on available drilling reports, field observation results and in-situ test data; constructed numerical model for gas emission prediction, combined with theories both Numerical Theory I and gas geology; and concluded how reservoir properties influence gas emission. The steps are as belows:1)screen out control factors for qualitative and quantitative research, including depth, thickness, floor lithology, ash content, moisture content, total sulfur, coal rank, maceral groups and tectonic indicator et al.;2) characterize each parameter for further analysis:observe fracture in coal under mine and microscope, measure fracture length and width, research micropores type and there connectivity, describe reservoir isothermal constants, permeability, gas content, specific surface and gas pressure by experiment and in-situ test;3) divide recovered area into smaller blocks, distribute every parameter selected to small grid, compare and screen the main control factors and establish multivariate function on gas emission and its influential factors;4) divide un-mined area into smaller blocks, distribute every parameter selected in step3to small grid, predict gas emission combined with function established in step3and factors characterized in step4. After analysis about reservoir properties influence on gas emission, it’s concluded that:1) coal in this area has been strongly destroyed so the Protodyakonov’s coefficient of coal in studied area is too low, between0.17to0.22, indicating low permeability of reservoir because coal fine is easy to block fracture which is the migration pathway;2) specific surface test results depict that there are both open and blind hole, while mainly blind hole; and observations under microscope confirm that micropore, which methane is desorbed on, is well developed;3) The values of isotherm constant a, b are a little bit large, which indicates coal has strong adsorption capacity. The desorption gas volume is low when the gas pressure declines from5MPa to1MPa, which depicts that gas cannot release from coal easily. When the gas pressure is lower than IMPa, the gas desorption rate ascends dramatically, and the coal and gas emission is more likely to happen, thus this pressure interval becomes the pretty significant part of gas prediction.4) The average permeability of target seam is0.42md. Coal in15061face and12201face individually have highest and lowest permeability which is0.57md and0.29md respectively.5) there is negative relationship between specific surface and fault displacement, coalseam depth and tectonic indicator, while positive relationship with coal rank (Ro), vitrinite content (VC), ash content (A), moisture content (M) and inertinite content (IC); significance test result indicate that the T-statistic of VC, D, M and TI is greater than the critical value (2.660) at0.01level; that of Ro, A, IC and fault displacement is greater than the critical value (1.671) at0.1level; This indicates that those parameters including VC, D, M and TI have significant influence on specific area, while Ro, A, IC and fault displacement have little effect on specific area. Specific area in the whole mine is lower in the middle part, while the higher value locates at13and16mining district, in which the specific value is greater than0.8m2/g, and the lower value lies in12district, where the specific value is0.4m2/g.6) The isothermal adsorption constant is proportional to the Ro, specific surface, vitrinite content, throw of the fault, burial depth, inertinite content and the tectonic complexity, while it is inversely proportional to ash content as well as water content, significance test result indicates that the T-statistic of D is greater than the critical value (2.660) at0.01level; that of VC and M is greater than the critical value (1.671) at0.1level; The T-statistics test illustrates that the burial depth, vitrinite content and water content are the3main independent variables that have profound effect to isothermal adsorption content(VL), whilst the influence of other6independent variables including Ro, specific surface, ash content, fault throw, inertinite content and the complexity of fault is quite inferior. In this paper, it has been predicted that the value of VL diffuses variably in the whole field with high heterogeneity and the maximum value might be35m3/t, while the minimum is only23m3/t. The value of VL in most area of the11panel could be as high as32m3/t, whereas in other panels, the VL is not constant.7) The gas content is proportional to coalbed thickness, gas pressure, vitrinite content, burial depth, isothermal adsorption constant(VL), water content and inertinite content, while the relationship between the gas content with the20m sandstone ratio,40m sandstone ratio, specific surface, the throw of fault, ash content, Ro, Dazhan sandstone thickness, the tectonic complexity is inversely proportional, significance test result indicate that the T-statistic of GP, specific surface, and Dazhan Sandstone (DS) is greater than the critical value (2.660) at0.01level; that of20m-SR, Ro, A, D, M and VL is greater than the critical value (1.671) at0.1level; that of40m-SR, fault displacement, T, A, D, IC and TI is greater than the critical value (1.671) at0.1level; The T-statistics test indicates that the8main factors (gas pressure, specific surface, the thickness of Dazhan sandstone,20m sandstone ratio, Ro, vitrinite content, water content, VL) are more likely to affect gas content than other7independent variables(40m sand stone ratio, fault throw, coalbed thickness, ash content, burial depth, inertinite content and tectonic complexity).Gas content in the whole field changes dramatically, ranging from3m3/t to16m3/t. From the northwest to the southeast of the field, gas content increase gradually, with a high gradient. Gas content is high in the southwest of the unmined area, while relatively low in northeast as well as partial area in the middle, with gas content less than10m3/t.8) Gas pressure is proportional to the coalbed thickness, specific surface, gas content, burial depth, Dazhan sandstone thickness and tectonic complexity, while is inversely proportional to the throw of faults, significance test result indicate that the T-statistic of D, DS, and specific surface is greater than the critical value (2.660) at0.01level; that of T, GC and TI is greater than the critical value (1.671) at0.1level; that of fault displacement is greater than the critical value (1.671) at0.1level; The T-statistics test demonstrates that the coalbed thickness, specific surface, burial depth, Dazhan sandstone thickness and tectonic complexity influence the gas pressure to some great extent, while the effect of fault throw on the gas pressure is not that apparent.9) The gas emission is proportional to gas content as well as gas pressure, which is inverse with the relationship between the gas emission and specific surface and VL. significance test result indicate that the T-statistic of GP and GC is greater than the critical value (2.660) at0.01level; that of VL is greater than the critical value (1.671) at0.1level; The T-statistics test shows that the gas pressure, gas content and specific surface have large effect on gas emission while the effect of VL is small. Gas emission shows an upward trend from northeast to southwest, and distributes heterogeneously in some areas. Gas emission tends to be quite higher in12panel,14panel,16panel than in others.10) Gas emission is primarily controlled by gas pressure which is dominantly influenced by burial depth and Dazhan sandstone thickness. Therefore, coalbed burial depth is the most critical factor which controls the gas emission. Due to the low level of tectonic degree, the gas was preserved quite well in the coalbed, and the fragile coal contributes to the lack of gas flowing path, In this study area, Dazhan sandstone prefer to make the gas pressure increase rather than make the gas escape.There is an unconspicuous negative relationship between gas emission and specific surface&Langmuir volume which indicates gas pressure and gas content weaken the effect of specific surface and Langmuir volume on gas emission. The above analysis provides evidence from the other side that the characters of gas pressure and gas content should be the two key parameter for gas prevention in non-mining areas. In order to give effective gas prevention rules in non-mining areas, gas pressure analysis for non-mining areas should be put on the first place. At present, there are only minor structures found in extracting face in known areas, however it does not mean there is no fault in unknown areas. Detecting minor faults, investigating the effect of faults on gas pressure and predicting gas emission based on relationship between faults and gas pressure should be the first job for further gas emission prevention.更多还原