A STUDY OF THE PERFORMANCE AND CHARACTERIZATIONS OF CLEANUP FLUIDS FOR RESERVOIRS DRILLED BY USING OIL-BASED MUD

Document Type : Research Paper

Authors

1 Petroleum Engineering Department, School of Engineering and Sciences, Curtin University. CDT 250, 98009, Miri, Sarawak, Malaysia

2 Geology Department, Faculty of Sciences, Liverpool University, Liverpool, United Kingdom

Abstract

The correct selection of the reservoir drilling fluid is critical to achieve the ultimate aim of minimizing formation damage for the completed such wellbores. This study evaluates the performance of a standard Oil Based Mud (OBM) to drill horizontal wellbores, concentrating on its formation damage characteristics and the Flow Initiation Pressures (FIP) required for production to flow through the filter-cake. For heterogeneous reservoirs, the study shows that in low permeability rocks the damage is relatively low but the FIP is high. Conversely, for high permeability rocks the FIP is low but formation damage is relatively high. If the drawdown pressure available from the reservoir is low, then we have the scenario where inflow will occur predominantly from the higher permeability formations which could be badly damaged but little inflow will occur from the relatively undamaged lower permeability rocks. In terms of maximizing production, this is obviously a less than optimal scenario. With this in mind, evaluations were conducted of cleanup fluids to gauge their effect on lowering the FIP of the OBM filter-cake. Various fluids were screened for their mud removal performance which would potentially indicate good OBM ‘chemical breakers’. Mud parameters such as oil: water ratio, base oil type and emulsifier content all affected the efficiency of the cleanup fluids. The best cleanup fluids were then utilized in a series of core tests to evaluate their effectiveness in reducing the filter-cake FIP.

Main Subjects

JES. Journal of Engineering Sciences
Volume 41, No 2
March and April 2013
Pages 702-723

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