Application of NMR Relaxometry in Petrophysical Properties Determination and Pore Structure Characterization for Clastic and Carbonate Rocks

Abstract

Abstract This paper discusses the use of Nuclear Magnetic Resonance (NMR) relaxometry to effectively determine the porosity and irreducible water saturation of rocks. The rapidity, efficiency and lack of influence on the core sample integrity actualizes the development of methodological approaches for experiment procedures and interpretation of measurement results in order to increase the information content of the method [24]. The paper presents the results of NMR investigation of clastic and carbonate rocks at full water saturation, irreducible water saturation and residual gas saturation, trapped during spontaneous imbibition. The first section of the paper presents possibility of NMR to evaluate separated distribution of pores and throats by size, which provides characterization of pore space structure of the reservoir and distribution of fluids by different types and the degree of bonding with rock surface. The second section presents results of suggested "subtractive distributions" of transverse relaxation time (T2) for characterizing various elements of the pore space and obtaining their distributions according to the volume ratio. The third section presents technique for determination of the irreducible water saturation and gas saturation trapped during spontaneous imbibition based on the T2 cutoffs. And fourth section presents review and consideration regarding possibilities and limitations of the NMR method in determination throat size distributions and capillary pressure curves modeling. In the conclusion the future research directions from current conducted researches have been suggested. The matters concerned in this research provides an insight into mechanism of fluid displacement through the drainage and spontaneous imbibition processes. Suggested techniques of investigations and data interpretation intended to improve understanding of rock pore space structure and reservoir properties.