Determination of In Situ Wettability Using Wavelet Analysis and Nuclear Magnetic Resonance Log Data

Unambiguously determining irreducible water saturation $$\left({S}_{\rm{wirr}}\right)$$ S wirr poses a formidable challenge, given the availability of multiple independent methods. Traditional approaches often depend on semi-experimental relationships derived from simplified assumptions. These methods, originally designed for oil sandstone reservoirs, result in varying $${S}_{{\text{wirr}}}$$ S wirr values when employed in carbonate gas reservoirs. Nuclear magnetic resonance (NMR) is the most advanced technique for determining $${S}_{{\text{wirr}}}$$ S wirr . While highly accurate, the NMR-based method necessitates the laboratory measurement of the transverse relaxation time $$\left({T}_{2}\right)$$ T 2 cutoff. Laboratory-based $${T}_{2}$$ T 2 cutoff determination is resource-intensive and time-consuming. This research aims to develop a robust model for determining $${S}_{{\text{wirr}}}$$ S wirr in carbonate gas reservoirs by utilizing NMR well logging measurements and special core analysis (SCAL) tests. Various $${T}_{2}$$ T 2 cutoff values were initially employed to compute bound water saturation $$\left({S}_{{\text{bw}}}\right)$$ S bw at different depths to achieve this. Subsequently, the data points $$\left({T}_{2}, {S}_{{\text{bw}}}\right)$$ T 2 , S bw were graphed on a scatter plot to unveil the relationship between $${S}_{{\text{bw}}}$$ S bw and $${T}_{2}$$ T 2 . The scatter plot illustrates an exponential decrease in $${S}_{bw}$$ S bw with increasing $${T}_{2}$$ T 2 , forming the basis for the $${S}_{{\text{wirr}}}$$ S wirr model derived from this relationship. Finally, the parameters of the $${S}_{{\text{wirr}}}$$ S wirr model were fine-tuned using SCAL tests. Notably, this $${S}_{{\text{wirr}}}$$ S wirr model not only accurately yields $${S}_{{\text{wirr}}}$$ S wirr at each depth but also offers a dependable determination of the optimal $${T}_{2}$$ T 2 cutoff for the reservoir interval.

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Experimental investigation on the pore structure and Water Inrush Evolution Law of weakly cemented fault fracture zone with different filling gradations

Wu,

Huang,

et al. 2023

Geomech. Geophys. Geo-energ. Geo-resour.

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Water and mud inrush caused by fault is a geological disaster characterized by high frequency and huge destructiveness. It is important to study the evolutionary laws of water inrush in fault fracture zones with various filling types. The effect of filling gradation on the mesoscopic structure and seepage characteristics of fault fracture zones was investigated. The law of water inrush evolution and water inrush characteristics of fault-fractured zones with different filling gradations and strong zoning filling characteristics were studied. The results showed that for the larger Talbot gradation indices, the mass of water inrush and the fractal dimension of the lost particles were larger, the peak water pressure and the mass of the lost particles were smaller, and the duration of the initial impermeability stage was shorter for the same loading water pressure. For the fault fracture zones with strong zoning filling characteristics, the peak water pressure, the mass of water surges, and the mass of lost particles were larger, the fractal dimension of the lost particles was smaller, and the duration of the initial impermeability stage was shorter for the fracture zones with larger filling gradation were used as the initial impermeability zones. Furthermore, with larger filling gradation, we observed a greater proportion of large pores, a larger equivalent throat radius, higher pore connectivity, and coordination numbers. Filling gradation and confining pressure greatly affected the permeability of the fault. The permeability decreased by 98.71% when the Talbot gradation indices decreased from 1.25 to 0.6, and decreased by 58.4% when the confining pressure increased from 5 MPa to 15 MPa.

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Determination of In Situ Wettability Using Wavelet Analysis and Nuclear Magnetic Resonance Log Data

Cited by 6 publications

References 21 publications

Measurement and modeling of water content distribution during spontaneous imbibition in coal

Measurement and modeling of water content distribution during spontaneous imbibition in coal

An NMR-based model for determining irreducible water saturation in carbonate gas reservoirs

Experimental investigation on the pore structure and Water Inrush Evolution Law of weakly cemented fault fracture zone with different filling gradations

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