Monitoring Methods Using Earth Tides for Fluid Migration in Geological Reservoirs

Abstract

Jacob 2) Bredehoeft 3) 4),5) 6),7) 2. 2. 1. This study proposes and examines a practical technique for monitoring underground fl uid migration using tidal deformation of the Earth.The gravitational attraction of the bodies in the solar system causes deformation of the Earth, and the pore pressure of the geological reservoirs changes in response to such tidal phenomena.These pore pressure changes are related to the poroelastic parameter χ, which is a function of fl uid saturations in the pore space, and χ can be an indicator for monitoring the underground fl uid migration. χ can be an indicator for monitoring the underground fl uid migration. χ To retrieve the pressure changes caused by the Earth tide from fi eld-measured pressure data including long-term pressure trends and noises, a pressure-analysis algorithm based on the cubic spline interpolation and the least squares method was employed.A set of numerical experiments were performed and the results showed that a proper selection of the time-node span for the interpolation enabled retrieval of diurnal and/or semi-diurnal pressure fl uctuations. The developed algorithm was applied to actual fi eld data, which confi rmed that the diurnal and semi-diurnal features of the pressure fl uctuations can be explained by the Earth tide.The estimated χ values indicated the ar-χ values indicated the ar-χ rival of the displacing fl uid at the monitoring well, showing that fl uid migration can be monitored by analyzing the χ profi les. χ profi les. χ