摘要
中国含（油）气盆地广泛发育与煤系烃源岩共生或伴生的致密砂岩气,以四川盆地须家河组和鄂尔多斯盆地上古生界最为典型。受煤系烃源岩大范围面状蒸发式排烃和低缓构造背景影响,致密砂体内气体运移聚集过程中水动力和浮力作用相当受限,在这种低渗低速条件下,非达西渗流特征非常明显,形成气—水混杂的含气区。致密砂岩气驱水模拟实验中,渗流曲线形态主要受岩心渗透率大小的影响,渗透率值越低,则启动压力梯度越大,非达西现象愈加明显。致密砂岩注气驱水实验过程中,岩心的最大含气饱和度一般小于50%,主要分布在30%~40%之间,含气饱和度平均值为38%左右,与地下岩心所在气层的实际含气饱和度比较相近。岩心含气饱和度与渗透率呈较好的对数正相关关系,相关系数为0.891 5。致密砂岩气体单相渗流过程中,由于存在气体渗流的＂滑脱效应＂,低速非达西渗流特征异常明显,存在＂拟初始流速Vd＂。单相气体渗流曲线形态特征主要受岩心渗透率及环压大小控制,渗透率值愈小或者环压值愈大,则非线性段越长,临界压力越高,启动压力梯度越大（0.02~0.08MPa/cm）,拟初始流速则越大,非达西渗流特征越明显。致密砂岩气渗流机理研究表明,储层渗透率越低,启动压力越大,流速越慢,天然气运聚效率和含气饱和度较低。针对煤系致密砂岩气运聚机理实验室模拟研究,为揭示致密砂岩气富集规律和评价选区,同时为开发机理研究提供理论基础。
Tight sandstone gas from coal-measure source rocks is widespread in China,and is most characterized by the Xujiahe Formation of the Sichuan Basin and the Upper Paleozoic of Ordos Basin.Coal-measure source rocks expelled hydrocarbon evaporatively.Under the setting of gentle structure,the gas migration-accumulation in tight sandstone is featured by restricted hydrodynamic and buoyance.Under the condition of low permeability and speed,non-Darcy flow is quite obvious,forming gas-water mixed mid-high water-bearing gas zone.In the water drive experiment,the shape of percolation flow curve is mainly influenced by core permeability：The lower the permeability,the higher the starting pressure gradient,and the more obvious the non-Darcy phenomenon.In the gas drive water experiment of tight sandstone,the maximum core gas saturation is generally less than 50%（ranging from 30% to 40% and averaging at 38%）,similar to the actual gas saturation of the gas zone in the subsurface core.The core gas saturation and the permeability have correlative relationship,with correlation coefficient of 0.891 5.In the single-phase flow of tight sandstone gas,low-velocity non-Darcy percolation is obvious and proposed initial flow velocity（V_d）exists due to the slippage effect of gas flow.The shape of percolation flow curve in single-phase gas is primarily controlled by core permeability and circling pressure：the lower the permeability or the higher the circling pressure,the higher the starting pressure（0.02-0.08MPa/cm）,proposed initial flow speed,square gradient of the critical pressure;the nonlinear section would also be longer and the non-Darcy flow would be more obvious.In general,tight sandstone gas seepage mechanism study showed that the lower the reservoir permeability,the bigger the start-up pressure,the slower the flow velocity.The efficiency of natural gas and gas saturation is low.The laboratory simulation research on coal-measure dense sandstone migration accumulation mechanism,provides a theoretic foundation for reveal
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2016年第7期1143-1152,共10页
Natural Gas Geoscience
基金
国家科技重大专项(编号:2008ZX05001-001
2011ZX05001-001)
中国石油科技项目(编号:2014B-0608)联合资助
关键词
煤系致密砂岩气
煤成气
一维实验模拟
启动压力梯度
充注渗流机理
含气饱和度
四川盆地三叠系须家河组
Coal-measure tight sandstone gas
Coal-derived gas
A one-dimensional experiment simulation
Starting pressure gradient
Filling flow mechanisms
Gas saturation
Triassic Xujiahe Formation in Sichuan Basin
