塔南凝灰质火山碎屑岩储层岩石物理试验研究

Petrophysical experimental research in Tanan tuffaceous pyroclastic rock reservoir

在模拟地层温度、压力条件下,试验观测塔南白垩系南屯组、铜钵庙组的凝灰质砾岩、凝灰质岩屑砂岩储层的纵、横波速度,考察岩性、矿物含量、胶结方式和接触类型、密度、孔隙度、泥质含量、含水饱和度对火山碎屑岩声波速度的影响。在试验考查的范围内,发现:①致密凝灰质砾岩的声速明显高于储油物性较好的凝灰质砾岩和凝灰质岩屑砂岩的声速;②纵、横波速度随岩浆岩岩屑含量的增加而增大,随石英、长石含量的增大而减小;③相同孔隙度条件下,孔隙式胶结、线性接触岩石的纵、横波速度最大,基底式胶结、不接触-点接触岩石的纵、横波速度最小,纵波速度较横波速度对胶结类型、接触方式更敏感一些;④纵、横波速度随密度增大而增大,凝灰质岩屑砂岩的声波速度与密度存在较好的幂函数关系,纵横波速度随孔隙度、泥质含量增大而减小,凝灰质岩屑砂岩的声速与孔隙度和泥质含量有很好的负线性函数关系,但泥质(主要为凝灰质)的影响仅为孔隙度影响的1/5～1/10,可以忽略不计;⑤随着含水饱和度增加,纵波速度对流体变化比横波速度更为敏感,且声速变化幅度与孔隙度存在正相关关系。

Under the condition of simulated formation temperature and pressure, the compression and shear wave velocity of the tuffaceous conglomerates and rock-fragment sandstones of the reservoirs in K1 t, K1 n group of Cretaceous system in Tanan were measured. The effects of lithology, mineral content, cementation type and particle contact mode, density, porosity, shale content, and water saturation on the acoustic velocity of the tuffaceous pyroclastic rock were studied. Within the observation limits, some rules are found： ①The acoustic velocity of the fine tuffaceous conglomerates is remarkably greater than that of the tuffaceous rock-fragment sandstones with good physical property. ②The acoustic velocity increases with fragment content increasing, and decreases with quartz and feldspar content increasing. ③In the same porosity, the velocity of porous cementation and lineal contact rock is the biggest, the velocity of basal cementation and matrix-suppot-point contact rock is the smallest and the compression velocity is more sensitive to the cementation type and particle contact mode than shear wave velocity. ④The acoustic velocity increases with density increasing, and the velocity of tuffaceous rock-fragment sandstones keeps a good relation with density in form of power function. The aeoustie velocity decreases with porosity and shale content increasing, the velocity of the tuffaceous rock-fragment sandstones keeps a good relation with porosity and shale content in form of negative linear function, but effect of shale （ be made of tuffaceous） content is only 5-10 times as small as that of the porosity, hence can be neglected. ⑤With porosity increasing, compression wave velocity is relatively sensitive to fluid alternation, and the range in which velocity varies keeps positive correlation with porosity.