نوع مقاله : مقاله پژوهشی
نویسندگان
دانشکده مهندسی نفت و زمین انرژی، دانشگاه صنعتی امیرکبیر، تهران، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Well logging is one of the key tools in the evaluation of carbonate reservoirs, and acoustic data, in particular, have gained an important position in petrophysical and geophysical studies. In this regard, the present study focuses on the Kangan and Dalan formations in the Persian Gulf to compare the behavior of compressional (P) and shear (S) waves and to evaluate the role of each in assessing reservoir quality. In addition, the relationships between lithology, type and amount of porosity, permeability, and matrix density with wave velocity were analyzed. Furthermore, the dataset includes 418 m of core, 1388 plug samples, and a series of petrophysical and geological analyses from a single well. The results indicate that lithology is the main factor controlling wave velocity. Moreover, moldic porosity in limestones reduces velocity due to lower density and structural discontinuities, whereas intercrystalline porosity in dolomites results in higher velocities owing to preserved matrix continuity. Both compressional and shear waves show higher velocities at permeabilities below about 5 mD. As permeability increases up to this threshold, velocity decreases and then exhibits a gradual rise. Moreover, at low permeability, the strong framework connectivity of the rock increases velocity, while at higher permeability, the formation of continuous flow paths causes a gradual recovery of wave velocity. Furthermore, increasing dolomite content up to about 70% results in a continuous velocity increase, beyond which the effect becomes saturated. In addition, the presence of anhydrite has a positive effect at moderate amounts but reduces velocity at higher concentrations due to induced heterogeneity. Comparison of the two wave types shows that shear waves are more sensitive to lithological variations, whereas compressional waves are mainly influenced by porosity and fluid composition. These findings highlight the importance of using both P- and S-wave data simultaneously in well log analysis to improve modeling and qualitative evaluation of carbonate reservoirs.
کلیدواژهها [English]