火山岩气藏不同岩性核磁共振实验研究

利用核磁共振技术,并结合离心实验,确定出可动用流体对应的下限离心力为2.76MPa;由毛管力原理,计算出可动用喉道半径下限为0.05μm,确定了火山岩储层可动用下限实验标准。研究结果表明:火山岩储层不同岩性可动流体驰豫时间(T₂)截止值与渗透率的关系与砂岩可动流体T₂截止值的变化规律不同。火山岩岩样的可动流体T₂截止值随渗透率增大而减小,并与裂缝发育程度相关。不同岩性可动流体T₂截止值由大到小依次为流纹岩、熔结凝灰岩、晶屑凝灰岩、角砾熔岩、火山角砾岩。不同岩性火山岩储层岩样的可动流体百分数总体而言随渗透率的增大而增大,束缚水饱和度随渗透率的增大而减小。

Experimental study on different lithologic rock of volcanic gas reservoir using nuclear magnetic resonance technique

The low limit of centrifugal force for the movable fluid is 2.76 MPa, which is determined by nuclear magnetic resonance (NMR) technique and laboratory experiment on centrifugal force of fluid. The low limit of throat radius for movable fluid is 0.05 μm, which is figured out according to the capillary law. Those values are the experimental standard for determining the low limit of volcanic gas reservoir. The relation between T₂ cutoff value of the movable fluid and permeability of different lithologic rocks of volcanic reservoir is different from that of sandstone reservoir. T₂ cutoff value of the volcanic rock movable fluid decreased with the increase of permeability and was related to the development of fracture. The order of the T₂ cutoff value for the movable fluid of different lithologic rock is as follows: rhyolite, welded tuff, crystal tuff, breccia lava and volcanic breccia. The movable fluid percentage also increased with the permeability increase of different lithologic rock in the volcanic reservoir, while the saturation of irreducible water reduced with the increase of permeability.