煤层气群井排采井间干扰的流体场监测机理与方法

In order to solve the key scientific problems that the formation, the evolution, the degree of well interference in coalbed methane development with multi-well drainage, and their response mechanism form fluid geochemical field and fluid kinetic flied, the coalbed methane field of Southern Qinshui basin with large-scale production will be seclected as a case study, the samples of coalbed methane and formation water produced by coalbed methane wells in the montioring area will be collected systematically according to the timeframe，the experimental methods of coalbed methane component, stable carbon and chlorine isotope of methane, the concentration of the ions and the element content from the formation water will be adopted, the geochemical characteristics of coalbed methane and formation water in different production time of the same monitoring well and the different monitoring well in the same production time will be investigated combined with he data of coal reservoir engineering and coalbed methane drainage mangement. The spatial and temporal evolution law of fluid chemical field in coal reservoir of the monitoring area under multi-well drainage will be clarified especially，the spatial and temporal evolution characteristics of fluid kinetic field in coal reservoir characterized by the flowing bottom-hole pressure of coalbed methane wells and fluid potential in coal seam will be analyzed, the inherent relations between the evolution of fluid chemical field, the evolution of kinetic field and the formation, development of well interference under multi-well pattern drainage of coalbed methane will be built, the response mechanism of fluid field on well interference will be revealed under multi-well drainage of coalbed methane in CBM production area with vertical wells. The theoretical basis of monitoring on fluid field, and the monitoring method system of well interference under multi-well drainage of coalbed methane will be founded as predicted,those will provide the direct scientific evidences for the optimization of well pattern and the operating system of coalbed methane drainage during coalbed methane development.

针对煤层气开发群井排采过程中井间干扰的形成、演变、程度及其井区储层流体地球化学场、动力场响应机理这一关键科学问题，以沁水盆地南部规模生产的煤层气田为研究实例，选择监测井按时间周期系统采集煤层气井产出的气样和水样，采用煤层气组分测试、甲烷碳氢稳定同位素测试、地层水离子浓度测试和元素分析等实验方法，并结合煤储层工程数据和煤层气井排采生产数据，查明同一监测井不同生产时刻、同一生产时刻监测区不同监测井煤层气和地层水地球化学变化特征，重点阐明群井排采条件下监测区煤储层流体化学场时空演化规律，分析煤层气井井底流压和煤层流体势表征的煤储层动力场时空演化特征，建立煤储层流体化学场、动力场演化与井间干扰形成、发展之间的内在联系，揭示煤层气直井生产区群井排采井间干扰的流体场响应机理。预期创立煤层气群井排采井间干扰的流体场监测的理论基础和监测方法体系，为煤层气开发井网优化和排采作业制度优化提供直接科学依据。

本项目以沁水盆地南部规模生产的煤层气田为研究实例，选择监测井按时间周期系统采集了煤层气井产出的气样和水样，采用气体组分测试、甲烷碳氢稳定同位素测试、地层水离子浓度测试和元素分析等实验方法，并结合煤储层工程数据和煤层气井排采生产数据，查明了同一监测井不同生产时刻、同一生产时刻监测区不同监测井煤层气和地层水地球化学变化特征，重点阐明了群井排采条件下监测区煤储层流体化学场时空演化规律，分析了煤层气井井底流压和煤层流体势表征的煤储层动力场演化特征，建立了煤储层流体化学场、动力场演化与井间干扰形成、发展之间的内在联系，揭示了煤层气直井生产区群井排采井间干扰的流体场响应机理。. 研究结果如下：. 1) 地下水流体势整体上由东向西及由南向北降低，监测时段内储层压力经历了反转、分异及不均衡压降期3个阶段，与煤层气生产的无井间干扰、弱井间干扰及不均衡井间干扰期相对应；在生产监测区内初步形成了井间干扰，且井间干扰处于不均衡井间干扰期，干扰程度相对较弱。. 2) 煤层气组分、稳定同位素、地层水的总矿化度、地层水电导率、地层水碳酸盐硬度、地层水中元素含量呈周期性波动变化；煤层气组分和稳定同位素变化与组分分馏、同位素分馏、排采速率及井间干扰有关，产出地层水的离子浓度、矿化度、硬度及元素含量变化与煤层气井排采强度、井间干扰、物源及元素自身的性质有关。煤层气组分、稳定同位素的波动性变化、离子浓度整体变化的一致性反映了区域性井间干扰的影响。. 3) 甲烷组分和二氧化碳组分的空间展布方向在采样时段内均多次改变，组分浓度的空间展布受局部煤层气产出组分浓度的影响；稳定同位素的空间展布主要经历了南北向展布及东西偏转的过程，碳、氢同位素的空间展布具有相似性，甲烷氢同位素的演化滞后于碳同位素；组分浓度差异及碳、氢同位素差异缩小揭示了井间干扰的影响，组分及同位素空间演化的多变性揭示了井间干扰处于初期且干扰程度较弱；地层水离子、元素的空间展布整体均表现出南北向及东西向的周期性偏转，元素的演化滞后于离子的演化；离子、元素的空间演化及两者演化不一致的原因可能有：元素及离子本身的性质、物源影响、排采井间干扰的影响。. 项目以煤层气排采流体动力场、流体化学参数及化学场为基础，确立了煤层气井生产井区井间干扰评价的原则和方案，评价方案能适用于不同煤层气生产区。