Detailed structural and stratigraphic Seismic interpretation for Kadanwari Area, central Indus basin, Pakistan (T-1548) (MFN 6866)

Abstract

Major objective of this research was to characterize reservoir potential and to exploit the channel reservoirs of Lower Goru Sands. These channel sands always put a challenge in front of geoscientists to exploit the channeled reservoirs in such a terrain for the evaluation of hydrocarbon potential. To identify and demarcate additional possible hydrocarbon plays within Kadanwari Field (Kadanwari 01, Kadanwari 03 and Gorwar 01) and the surrounding areas, sequence stratigraphic studies and structural interpretation have been carried out using well logs and 2D seismic lines. The research work utilizes the advanced seismic techniques like seismic sequence stratigraphic analysis, seismic attribute analysis along with the support of seismic interpretation, AVO modelling and petrophysical analysis of Kadanwari Area, Pakistan. Although the quality of the seismic data is not effective enough to resolve discrete geological features at deeper level due to complex structuration, but the seismic signatures somehow reveal very critical discontinuities among the Goru reservoirs when aided by seismic attribute. Spectral decomposition allows comparison of various frequency ranges versus Lower Goru Sand response, depicting inverse relation of frequency with sands bed thickness. Clear zones of sand bodies with channel geometries are indicated by spectral decomposition technique and presence of bright spots is demarcated by instantaneous amplitude attribute at the level of Lower Goru E Sands makes it a potential reservoir zone of Kadanwari Area. Instantaneous phase attribute helped a lot in identification of seismic stratal terminations. The synthesis of sequence stratigraphic studies indicates that the long-known interpretation of the early to mid-Cretaceous successions represent a transition from shallow to deep marine rocks during the progradation of sedimentary wedges. During deposition, the effects of the Kandra paleo-high were significant with deposits effectively ponding against it as progradation continued to infill accommodation. The main gas fields in this succession are developed in the shallow-marine sands at the top of this wedge. The basinal turbidite sandstones and/or lowstand delta sands have the potential to provide underexplored or new exploration opportunities. Deposition under different 3rd order cycles of sea-level change had a profound influence on the regional development of reservoirs with the main fields occurring in transgressive/regressive sandstones sealed by the overlying shales. Second ii and third order sequences (1-3 Ma) were marked in research work. Prograding Wedges, encompassing K50 to K60 Sequences shows that the basin was under filled at the time. These prograding clinoforms would be expected to have basin floor fan and lowstand delta top. AVO models for Lower Goru E and G sands were prepared by using well data and empirical relationships for the identification of class of sand in Kadanwari Field.