• Evaluation of the loss of functionality of xanthan gum based drill-in fluid and its impact on coiled tubing drilling

      Dosunmu, Idowu; Misra, Debasmita; Chukwu, Godwin A.; Mongrain, Joanna; Khataniar, Santanu (2010-08)
      "A challenge that has recently arisen in coiled tubing drilling is the loss of functionality of xanthan gum drill-in fluid with drilled depth in the well. The overall objective of this study is to analyze and assess the causes for this loss of optimal functionality. Twenty-four field samples from two field cases and five laboratory prepared samples were tested to study the changes in theological parameters, salinity effects and compatibility with shale formations. It was observed that the fluid's functionality was directly related to low shear rate viscosity, which is affected by xanthan gum concentration and the ionic strength of the solution. X-ray diffraction analysis revealed a loss in the ionic strength due to the depletion of potassium chloride (KCI) with drilled depth. Experimental laboratory work confirmed the decrease in fluid viscosity as a result of KCI depletion. This decrease could result in a reduction of the cuttings carrying capacity of the drill-in fluid. A major implication of this work was the understanding gained on the reduced compatibility between xanthan gum solutions and the encountered shale formations; this happens due to KCI loss. As a result, possible stuck pipe conditions could be encountered if the reduced compatibility is left unaddressed"--Leaf iii