Oil viscosity evaluation method of the shale oil formations with NMR logging
With the exploration and development of the shale oil and gas resources,formation evaluation is playing an important role.Specifically,the viscosity of crude oil is a critical factor influencing the development strategies,productivity,outputs,and recovery rates in the shale oil reservoirs,which is the fundamental parameter of fluid identification and quantitative assessment.However,it is difficult to accurately estimate the viscosity index of crude oil due to the diverse occurrence states and complex flow mechanisms in shale reservoirs.Therefore,it is very necessary to establish an evaluation method for the viscosity of crude oil in the shale oil reservoirs.This paper analyzes and identities the relationship with the crude oil viscosity,T2 logarithmic mean value,and absolute temperature based on the foundational theory with Nuclear Magnetic Resonance(NMR).Furthermore,the NMR measurement has been performed to characterize the variation the T2 relaxation time at different temperatures with bulk oil from shale reservoirs.A model has been built to predict the viscosity of crude oil based on the T2 logarithmic mean value at the different temperatures.Finally,through the NMR experiments with the shale core samples saturated with crude oil,we built a similar model to predict the crude oil viscosity with the T2 logarithmic mean value from NMR logging in the reservoir conditions from downhole.Application results of NMR well logging data demonstrate that the relative error between the calculated moveable oil viscosity index and measured crude oil viscosity from field well tests is lower than 5％,which meaning the proposed method is accurate and effective.
Viscosity of crude oilShale oilFluid occurrence stateT2 spectrumNMR with different temperatures
NETL
NSTL
万方数据
