Development of a Chemical Treatment for the Management of Wellbore Tar Adhesion

摘要

Incursion of subterranean tar into the wellbore during and/orrnafter drilling has the potential to result in a variety ofrnproblems. If the tar is soft and deformable, it may ‘refill’ thernwellbore and require additional drilling time and casingrnoperations. An additional problem is adhesion or accretion ofrnthe tar directly onto the drillstring or bottom-hole-assemblyrn(BHA). Such fouling of the drillstring/BHA often requiresrnunplanned tripping to physically remove the adhered tar. It isrnalso conceivable that the tar-related problems may ultimatelyrnresult in the hole being plugged and abandoned. For thesernreasons, an approach has been developed to (1) emulate thernreported wellbore accretion, and (2) develop lab-basedrnapproaches to help minimize/reverse the tar adhesion.rnInvestigation of tar accretion onto steel rods/tubes with a Gulfrnof Mexico tar was studied in a synthetic-based mud, tornevaluate possible avenues of remediation. In addition tornevaluating the conditions necessary to induce tar accretion inrnthe laboratory, further studies were performed to affectrnreversal of the intentional accretion and also to help preventrninitial accretion. Included are the results from the inducedrnaccretion and various additive-based attempts to mitigate therntar adhesion.rnIn order to induce lab-based accretion, it proved necessary torndevelop a testing method to emulate the scope of tar accretionrnobserved in the field. This methodology is herein describedrnalong with the optimized fluid system. Of specific interest inrnthis study is the ability to use this novel fluid either as arnsweep, spot or additive as a means to help reduce the inherentrn‘tackiness’ of the tar and thereby help reduce/prevent thernadhesion to the emulated drill string. The fluid treatmentrndeveloped is environmentally acceptable and uses a novelchemical composition which proved successful in reversingrnand preventing tar accretion under the laboratory experimentalrnparameters.