Seismic Attributes, Cuttings Analysis and GDE Mapping, Enabling Reservoir Quality Prediction. An Example from Pakistan

Abstract

A proof-of-concept reservoir quality prediction project was undertaken for the Lower Cretaceous section of the studied field located in Pakistan. This project utilised and integrated three techniques: seismic attributes, drill cuttings analysis and gross depositional environment (GDE) mapping. This paper focuses on the GDE aspects and in particular the integration of seismic attributes, wireline, core and drill cuttings analysis that define these maps. Moreover, the results of GDE mapping and reservoir quality analysis revealed the following: • GDE maps illustrate that the entire reservoir package was formed in a transgressing, mixed tidal to fluvial delta system which terminated into a central mud basin. • Reservoir quality is controlled be the interaction of grain size and quartz inhibiting grain coating chlorite. Chlorite grain coats are most common in the northeast part of the field where the greatest production rates occur. In contrast two wells with lower production rates are located in a sediment bypass zone that does not allow for chlorite development, where quartz cement volumes are thus higher with resulting lower permeabilities. The key reservoir quality observations independently corresponded with production volume trends indicating the relevance of spatially integrating all available data.