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Evaluation of Effect of Different Concentrations of Shale on Rheological Properties of Water-Based Mud

Author Affiliations

  • 1Department of Petroleum and Gas Engineering, Faculty of Engineering, University of Port Harcourt, NIGERIA
  • 2 POCEMAConsultants, Plot 6 Azunda Wobo, Port Harcourt, Rivers State, NIGERIA

Res.J.chem.sci., Volume 2, Issue (10), Pages 13-19, October,18 (2012)


Wellbore instability encountered while drilling shale formations is a worldwide problem. Despite much experience and considerable research, drilling and completion operations continue to be plagued by various hole problems attributed directly to shale formations. This results in substantial yearly expenditure for the drilling industry. There is utmost need to evaluate the concentration of shale contamination on mud that could result to these associated well instability problems. This study therefore was undertaken to evaluate the effect of different concentrations of shale on the rheological properties of water- based mud(WBM). This was done by contaminating 8.5PPG WBM with 1.0%, 2.0%, 4.0%, 7.0% and 10.0% respectively of typical shale sample from the Nigerelta egion of Nigeria. The rheological values were determined using viscometer and the Plastic viscosity evaluated as applicable. Test results indicated that the rheological values increased showing a spike as the shale concentration increased. The increase in rheological values were 9.5%, 42.9%, 52.4%, 66.7% and 114.3% respectively for the various contaminations as indicated above. To avoid non-productive time resulting from hole instability problems caused by shale, when drilling is expected to encounter shale zones, proper design of the drilling fluids that will inhibit shale swelling as well as prudent step to avoid mud contamination by shale is imperative.


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