Reservoir Characterization Of Thin Bed Sand Reservoirs Of Lower Goru Using Integrated Approach, Lower Indus Basin, Sindh, Pakistan

Abstract

The current research comprised of study of NIM-TAY Gas Field, which was discovered in 1997. Geographically, the study area lies in Tando Allah Yar and Hyderabad districts of Sindh Province, Pakistan and geologically the research area is situated in Lower Indus basin, which is most explored basin of Pakistan with immense hydrocarbons potential. Research objective was to delineate the reservoir potential of thin sands of Early Cretaceous Lower Goru Formation. Integrated data sets: 3D seismic data and well logs data are used to identify and map the lateral extend of Upper Sands of the formation. The B and C-interval sands are targeted sands, which are the part of Lower Goru Formation. Normal faults are observed in the study area which indicates that the area lies in extensional regime, forming a horst and graben structures. The B-Sand was marked as top of the Lower Goru Formation in two wells TAY-01 and 03 but this sand interval is missing due to presence of fault at TAY-02 well confirmed by seismic data interpretation. Pay zone 46m and 51.6m thick of B-Sand zone in TAY-01 and 03 is identified as a main reservoir sand with maximum effective porosities 12% and 19% respectively, where the zone 3.8m of C-Sand identified in TAY-02 well with effective porosity 20% and is confirmed through intensive well log interpretation. Seismic interpretation and petrophysical analysis of C-Sand interval helped to map the reservoir interval with net pay thickness 3.8m considered as thin bed reservoir. The well correlation using well logs confirms the missing of B-Sands at TAY-02 well based on well log behavior of the formation. The Model Based Inversion was carried out to study the thin sand bed of C-Sand on the available post-stack data with the generation of initial model derived from seismically marked horizons and well data. Results from Inverted Impedance data confirmed the missing strata of B-Sand in TAY-02 possible due to uplifting of a normal fault. The porosities model generated from the inversion are closely matching with the well-based porosities. On the basis of Inverted Impedance data an anomalous zone is identified between TAY-01 and TAY-03 with same impedance response of C-Sands zone ranging from 8600 to 8700 (g/cm3-m/s) and confirming thin structure. It is recommended to test this anomaly to confirm the results.