THE GEOLOGICAL SELECTION OF DRILLING-FLUIDS IN HORIZONTAL WELLS

The drilling of horizontal wells has led to new demands on drilling fl uid design. Less damaging drill-in fluids are formulated after extensi ve geological testing of the productive formation. This paper describe s the main tests undertaken and some of the fluids commercially availa ble. Geological analysis of the formation is followed by the testing o f a proposed fluid, including extended exposures of the formation and fluid in conditions imitating those: found downhole. Potential product ion impact is assessed by a return permeability test. With a clear und erstanding of what causes formation damage, drill-in fluid chemistry a nd properties can be engineered to prevent damage. Glycol, formate and sized calcium carbonate particle technologies are described.