Reservoir Evaluation and Development ›› 2018, Vol. 8 ›› Issue (5): 8-13.

• Reservoir Geology • Previous Articles     Next Articles

Experimental study on identification of influencing factors of igneous gas and water layer by longitudinal and shear wave velocities

Jia Jun1,2,Li Chang3,Wang Liang2,Zhao Ning2   

  1. 1. College of Resource and Environmental Engineering, Mianyang Normal University, Mianyang, Sichuan 621006, China
    2. School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China
    3. Hangzhou Geological Institute, CNPC, Hangzhou, Zhejiang 310023, China
  • Received:2017-12-13 Online:2018-10-26 Published:2018-12-05

Abstract:

In order to reveal the link between the physical mechanism of identifying gas and water zones in igneous rock with longitudinal and transverse waves' velocity, and the internal factors of reservoirs, and guide the identification of fluid types in igneous rock, the Carboniferous igneous rock core of the Junggar Basin was selected, and its longitudinal and transverse waves' velocities were measured via the ultrasonic pulse method . The longitudinal and transverse waves' velocities of the core in the dry state and the water-saturated state were obtained. In addition, the influence of the internal factors of reservoirs like the fluid types, porosity, density and lithology on elastic wave velocity were analyzed. The research showed that the gas-bearing state of the formation would cause the significant decrease in both the longitudinal wave velocity and the ratio of longitudinal to transversal wave velocities, but had a small impact on transversal wave velocity. In formations with low porosity, it was difficult to identify the fluid types because the difference in the characteristics of the longitudinal and transverse waves' velocities in gas and water zones was weakened. Due to the complex lithology in igneous rock and the great influence of SiO2 content on elastic wave velocity, fluid types should be identified by different lithology. Based on the above conclusion and in order to highlight logging responses of fluids, VP/Vs-Rt crossplots were established by different lithology to identify gas and water zones in tested formations in the research area. For intermediate-basic rock and acid rock, the Vp/Vs values are 1.85 and 1.75, respectively, which can be used to distinguish the gas zone and the water zones effectively; however, due to the influence of low porosity, it is difficult to effectively distinguish between the gas zone and the gas-water coexistence zone.

Key words: carboniferous igneous rock, longitudinal and transverse wave velocity, physical mechanism, influential factors, fluid identification

CLC Number: 

  • P631