Understanding and Overcoming Challenges of Carbonate Reservoir Matrix Stimulation – The Case of an Offshore Abu Dhabi Reservoir

Abstract

A mature offshore Abu Dhabi oil field produces from a heterogeneous carbonate limestone reservoir with an important column of bottom aquifer. The reservoir heterogeneity is characterized by presence of kurst filled with fine materials at top section, conductive faults, fractures, and significant variation of other rock properties. Most of the main faults cross from the top of the oil column all away down to the bottom of the aquifer. Meanwhile, the field development mainly consisted of horizontal producers targeting the upper section of oil column with peripheral deviated water injectors to sustain reservoir pressure. Generally, producers start with high initial oil rates, but the early decline is steep due to rapid water cut increase resulting into lower well head pressure. Production profiles from PLT combined with FMI indicate that production and water influxes are contributing mainly from the fractured sections of the horizontal drain or through conductive faults. In the meantime, important matrix segments of horizontal drains present very low or no contribution to production. As a solution, surface bull heading and targeted zonal stimulations were performed, which yielded mixed results. This paper focuses on the analysis of the latest targeted matrix segment stimulation results, which include candidate selection background, description of stimulation method and operations, pre and post stimulation production performance analysis, analysis of main factors affecting carbonate matrix stimulation, and a summary of findings with overall implication to carbonate reservoir matrix stimulation.