一种表征煤储层压力与流体饱和度关系的数学模型  

A mathematic model for characterizing the relationship between coal reservoir pressure and fluid saturation

作　　者：孙政[1] 李相方[1] 徐兵祥 彭泽阳 孙逢瑞 张涛[1] 冯东[1] 陈宇[1] SUN Zheng;LI XiangFang;XU BingXiang;PENG ZeYang;SUN FengRui;ZHANG Zao;FENG Dong;CHEN Yu(Key Laboratory for Petroleum Engineering of the Ministry of Education, School of Petroleum Engineering, China University of Petroleum, Beijing 102249, China;New Energy Research Center, CNOOC Research Institute, Beijing 100028, China)

机构地区：[1]中国石油大学(北京)石油工程学院,石油工程教育部重点实验室,北京102249 [2]中海油研究总院新能源研究中心,北京100028

出　　处：《中国科学：技术科学》2018年第5期457-464,共8页Scientia Sinica(Technologica)

基　　金：国家重大科技专项项目(编号：2016ZX05042,2016ZX05039); 国家自然科学基金重大项目(编号：51504269,51490654); 贵州省非常规天然气勘探开发利用工程研究中心项目(编号：GCZX2016030)资助

摘　　要：目前,针对生产过程中煤储层内部气、水两相渗流的研究尚薄弱,已建立的煤层气产能预测模型或产能分析方法中,一部分假设煤储层内部为单相渗流即单相水或单相气,一部分忽略流体饱和度和压力变化梯度,另一部分通过物质平衡方程建立平均地层压力与平均含水饱和度间关系,进而研究储层饱和度分布对气井产能的影响,但平均含水饱和度无法表征储层内部的饱和度分布.故现有模型均未考虑储层流体饱和度分布特征对气井产能的影响,导致现有产能模型预测值与实际煤层气井产出动态始终存在较大误差.鉴于此,根据气、水两相渗流微分方程,考虑应力敏感、基质收缩与气体解吸效应,建立了一种能够表征煤储层压力与流体饱和度间关系的数学模型.结合气、水两相相渗曲线与各生产时刻的储层压力分布曲线,提出迭代算法求解该模型,得到各生产时刻的流体饱和度分布规律.该模型的可靠性通过与商业数值模拟软件结果对比得到验证.该模型的提出填补了目前煤层气开发理论的空白,有助于准确计算气、水两相拟压力,为煤层气藏产能的准确预测奠定理论基础.At present, the research on the gas water two-phase flow during the development process of coalbed methane reservoirs（CMB） is still weak. Numerous production prediction models and transient production data analysis methods have been developed. However, part of these previous models assume the single water or gas phase within the coal seams, the other part overlook the gradient of fluid saturation and pressure and another part investigate the effect of fluid saturation distribution on productivity by utilizing the concept of average saturation, which is obtained through the derivation of material balance equation in CMB reservoirs. Notably, the average saturation cannot capture the feature of saturation distribution in the coal seams. Therefore, the existed models do not take into account the influence of fluid saturation distribution characteristics on gas well productivity, which result in relatively large error between the present productivity model and the actual CMB wells. In these regards, according to the gas and water two-phase seepage differential equation, considering the stress sensitivity, matrix shrinkage, gas adsorption/desorption effect, this research establishes a mathematical model characterizing the relationship between formation pressure and saturation. Combined with gas-water two-phase relative permeability curve, the model can be solved to obtain the saturation distribution on the basis of reservoir pressure distribution.Moreover, the reliability of the model is verified against commercial numerical simulation software with excellent agreements. The proposed model fills the gap of CMB development theory, and significantly contributes to the precise calculation of the gas-water two-phase pseudo pressure. In addition, it lays a theoretical foundation for accurate prediction of CMB productivity.

关 键 词：煤层气藏 压力分布 流体饱和度分布 相渗曲线 拟压力 

分 类 号：TD841[矿业工程—煤矿开采]