Capillary Pressure Curves from Nuclear Magnetic Resonance Log Data in a Deepwater Turbidite Nigeria Field - A Comparison to Saturation Models from SCAL Drainage Capillary Pressure Curves

Abstract

The DW Turbidite field in Deepwater Nigeria has limited SCAL data on drainage capillary pressure curves used, traditionally, in building saturation-height functions for application in 3D static and dynamic models. An alternative approach to derive capillary pressure curves from Nuclear Magnetic Resonance (NMR) T2 distributions, developed by Volokitin et al, has been tested in one of the key reservoirs in the DW Turbidite North field and compared to mercury injected capillary pressure (MICP) data from a full-bore core across the reservoir. The alternative approach relies on an underlying assumption that a relationship exists between porebody radius (as represented by the NMR T2 distribution) and pore-throat radius (which drives capillary behavior). An algorithm has been applied that uses a T2 cutoff such that the sum of the bound and moveable fluid spectra amplitudes matches the water porosity to correct for the presence of hydrocarbons. The hypothesis is the resulting relationship (between the NMR T2 distribution and pore-throat distribution) embedded within a proportionality parameter, κ. The hypothesis was tested on the three key facies (CSA - Channel Storey Axis, CSM - Channel Storey Margin & ICTB - Inter-Channel Thin Beds) identified in the reservoir. Field-specific proportionality parameters were determined from which NMR T2 capillary pressure curves have been derived. Comparison between the derived capillary pressure curves and the SCAL (MICP) data provide confidence that this technique can be applied in the absence of SCAL data.

Low Permeability Gas-Bearing Sandstone Reservoirs Characterization from Geophysical Well Logging Data: A Case Study of Pinghu Formation in KQT Region, East China Sea

“…The best type always corresponds to the highest quality and, thus, good hydrocarbon production [46]. However, formation pore structure cannot be consecutively characterized due to limitation of quantity that is caused by environmental and economic factors [47]. Nuclear magnetic resonance (NMR) logging has unique advantages in consecutively evaluating formation pore structures [48,49].…”

“…Nuclear magnetic resonance (NMR) logging has unique advantages in consecutively evaluating formation pore structures [48,49]. The common method to evaluate pore structure was to synthetize capillary pressure curves (P c ) from NMR logging; several techniques have been raised in the last 12 years [20,43,47,[50][51][52]. Volokitin and Looyestijn (2001) and Looyestijn (2001) proposed a linear scale function to transform the NMR T 2 distribution as a pseudo-P c curve to characterize formation pore structure [43,50].…”

Gas-Water Characteristics of Tight Sandstone in Different Charging Model in Xihu Sag, East China Sea Basin

“…Lysova(2011) has analysis the residual water depend on Magnetic Resonance Imaging(MRI) experiment of natural gas charging (Lysova, 2011), and some scholars placed CT imaging devices on the core displacement chamber (Masri , 2021) to analyze the changes in different parts of water saturation after displacement. According to centrifugal-NMR experiments, there are many articles on the distribution of core residual water (Arogun, 2011;Daigle, 2015;Shao, 2017;Chen, 2019). The fluidity of the reservoir fluid can be analyzed according to the centrifugal force.…”

Gas–Water Characteristics of Tight Sandstone in Xihu Sag, East China Sea Basin under Different Charging Models

“…There have been many articles focused on determining the distribution of core residual water according to the results of Centrifugal NMR experiments [9][10][11][12][13][14][15], through which the fluidity of the reservoir fluid can be analyzed.…”

“…The previous step was repeated until the natural gas had completely displaced the core, and little change was observed in the NMR T2 spectra and MRI images 8. The driving pressure was released to atmospheric pressure slowly, following which the core was removed from the device 9. The core was replaced with the next sample, and the experiment was repeated.…”