A novel pulse sequence and inversion algorithm of three-dimensional low field NMR technique in unconventional resources.

Compared with two-dimensional (2D) nuclear magnetic resonance (NMR) technique like correlations among the transversal relaxation time (T), the longitudinal relaxation time (T), and the diffusion coefficient correlation (D), three-dimensional (3D) NMR technique is superior with the complete measurement of T, T, and D simultaneously. It can solve the problem of overlaps in 2D correlation map and is helpful to characterize relaxation components in unconventional resources such as tight gas and oil shale. However, the existed 3D NMR technique is restricted due to the loss of short relaxation information and the inversion inaccuracy that caused by the incomplete measurement of the diffusion editing window.

An improved method for permeability estimation of the bioclastic limestone reservoir based on NMR data.

Permeability is an important parameter in formation evaluation since it controls the fluid transportation of porous rocks. However, it is challengeable to compute the permeability of bioclastic limestone reservoirs by conventional methods linking petrophysical and geophysical data, due to the complex pore distributions. A new method is presented to estimate the permeability based on laboratory and downhole nuclear magnetic resonance (NMR) measurements.

Geochemical characterization of Lucaogou Formation and its correlation of tight oil accumulation in Jimsar Sag of Junggar Basin, Northwestern China.

With the constant consumption of conventional oil and gas resources, unconventional oil and gas resources with great resource potential such as tight oil have gradually been valued and become the new exploration area. Jimsar Sag is the key tight oil exploration and development block in Junggar Basin of Northwestern China. Based on the data sets of geology, oil production test, logging, rock thin section, and geochemistry of Permian Lucaogou Formation (LCG), we studied the geochemical characteristics of hydrocarbon source rocks and their relation to the tight oil accumulation.

The inversion of 2D NMR relaxometry data using L1 regularization.

NMR relaxometry has been used as a powerful tool to study molecular dynamics. Many algorithms have been developed for the inversion of 2D NMR relaxometry data. Unlike traditional algorithms implementing L2 regularization, high order Tikhonov regularization or iterative regularization, L1 penalty term is involved to constrain the sparsity of resultant spectra in this paper.