Session: Postersession - P-050

A modified design of pulse sequence and inversion method for D-T2 2D NMR in Rock Physics

F. Wu¹*, Y.r. Fan¹, P.q. Yang², Y. Gao², Y.l. Zhang²

1. CNPC Key Laboratory for Well Logging in China University of Petroleum, School of Geosciences in China University of Petroleum, Qingdao, China
2. Shanghai Niumag Electronic Technology Co., Ltd., Shanghai, China

Faced with the increasingly complicated exploration targets, D-T2 2D NMR technology can't balance the range of diffusion coefficient and transverse relaxation resolution in practice. As the key technique of D-T2 2D NMR, the property of pulse sequence affects its application. A modified design of bivariate D-T2 pulse sequence based on pulsed filed gradient is proposed by comparison of six common used D-T2 pulse sequences, which balance the range of diffusion coefficient and transverse relaxation resolution successfully.

Schematic diagram of modified D-T2 pulse sequence on pulsed field gradient

In order to solve the difficulties of the existing D-T2 inversion methods cannot balanced the inversion efficiency and accuracy, proposes a joint TSVD inversion method which sets the echos from the second window as the main part supplemented by the echos from the first window.

The joint TSVD inversion method

The numerical simulation results based on different structural models indicate that the D-T2 modified pulse sequence and joint TSVD inversion method have wide application foreground in the exploration and formation evaluation for unconventional reservoir, and create favorable conditions for the development of D-T2 2D NMR technology.