Organic matter detection in shale reservoirs using a novel pulse sequence for T1-T2 relaxation maps at 2 MHz

SILLETTA, EMILIA V.; VILA, GABRIELA S.; DOMENÉ, ESTEBAN A.; VELASCO, MANUEL I.; BEDINI, PAULA C.; GARRO-LINCK, YAMILA; MASIERO, DIANA; MONTI, GUSTAVO A.; ACOSTA, RODOLFO H.

FUEL

ELSEVIER SCI LTD

Año: 2022 vol. 312

0016-2361

Quantification of organic matter and fluids contained in oil source rocks from shale plays is a fundamental goalfor the petrophysical and geochemical assessment of the production potential of a well. Laboratory 1H nuclearmagnetic resonance (NMR) is a fast, reliable, and non-destructive method widely used in the oil industry.Measurement of T1-T2 correlation maps have been found to be critical for identifying the presence of solidorganic matter, liquid hydrocarbons, and brine in these formations. However, the inherent long echo timesassociated with standard laboratory equipment for large sample volume challenge the detection of contributionfrom kerogen and viscous bitumen. In this work, we use a commercial low field NMR rock-core analyzer where anovel T1- T2*&T2 pulse sequence is implemented to enable the detection of solid organic matter by acquiring thefree induction decay after the first excitation pulse. This acquisition is followed by a train of refocusing pulsesthat generate multiple echoes from which liquid components are detected. A set of outcrop and well samplesfrom the Vaca Muerta Formation in Argentina, with a varying amount of total organic content, were measured.The signal intensity assigned to solid matter was correlated with RockEval 6 pyrolisis. The novel pulse sequencepresented here can be implemented in any commercial apparatus without the need for hardware modifications.