Automatic matching technology for determining acquisition parameters of formation rock T2-G experiment

Key words:  modified CPMG sequence  internal magnetic field gradient  acquisition parameters  automatic matching  numerical simulation

Abstract:

In order to solve the difficulties in determining the acquisition parameters such as t0 and NE1 when using the modified CPMG(Car-Purcel-Meiboom-Gill) sequence to measure the internal magnetic field gradient of formation rock, an automatic matching technology for determining t₀ and NE₁ was proposed after summarizing the empirical rules applied in the field:the T₂-G approximated distribution model of tested rocks is first constructed; then with the approximated model the response of T₂-G experiment is calculated by tuning t0 and NE1 using numerical simulation methods, and lastly the suitable t₀ and NE₁ are determined by using constraints from the optimal model. The accuracy and efficiency of the method is further verified in the T₂-G experiment using eight sandstone samples from different regions.