oa Reservoir characterization and reservoir modeling of tight gas reservoir of Guangan field, China

The Guangan field produces gas from a very thick Triassic sandstone reservoir that covers an area of 60 square km in southern China. A reservoir characterization study was undertaken to assist in proposing well locations. The model was based on geological, geophysical and engineering data available from 15 vertical and horizontal wells. This data was integrated and used to define different rock types of the sandstone reservoir based on to their reservoir properties. A static model using PetrelTM was used to visualize the reservoir distribution throughout the field. The interplay of initial composition, depositional environment and diagenetic overprint determine reservoir quality. Thin-section studies showed that the heterogeneity of the rock is controlled by grain size, pores, cementation and fractures. This results in a significant variation of reservoir characteristics. The importance of the varying diagenetic histories is that the major differences in initial composition and diagenesis are reflected in pore geometry, which controls reservoir properties. Flow-zones studies defined four zones that have similar fluid flow characteristics. The classification of these zones identified no-reservoir zones and the best reservoir zones in the rock. The defined reservoir zones have been compared to well-test results and production data. A net-sand model, based on seismic attributes, has been used to supervise the petrophysical model and flow-zone model. For the best exploitation we must choose the prime regions using 3-D models for locating new wells. The highest quality of the reservoir occurs in its upper part and recommended for coring, logging and perforation.