An Innovative Spacer System Designed with Biodegradeable Polymer andLoss Circulation Material to Aid in Formation Damage Control

摘要

In offshore drilling technology,spacers are used prior to the cementing job for wellbore cleaning andimproving cement bonding.Spacers are also used for remedial purposes such as formation damage controlor prevention of further formation damage.Lost circulation is one of the major issues encountered whendealing with a damaged formation and must be assessed immediately and ceased before further issues occur.This proprietary spacer contains a blend of coarse,granular,organic,biodegradable material and can sealup to 4 mm gaps.In this paper,we discuss an optimum spacer with a novel biopolymer and loss circulationmaterial which are used successfully for cementing jobs under challenging loss circulation conditions.This study explains the performance of this optimum spacer.The optimum spacer has been successfullyapplied on offshore wells specifically for preventing and remediating lost circulation issues whilecementing.The rheological properties of the spacer at both ambient and elevated temperature were analyzedand reported.The compatibility tests between the spacer and drilling fluid and cement slurry were alsoconducted along with the sealing properties of the spacer.The sealing properties were determined in a fluidloss cell with 20/40 frac sand,and were also tested through a particle plugging apparatus at various gapmeasurements.In this study,spacer compositions and densities were adjusted to examine effects on rheology and stabilityof the solids within the system at ambient and elevated temperature.Also,this novel spacer improved thecompatibility with synthetic/diesel-based drilling fluid and cement with less or no viscosification comparedto commercial spacers.In addition,the spacer shows to effectively seal 20/40 frac sand at 100 psi as wellup to a 4 mm gap at 1000 psi.The first case history for this technology has been successfully completedand are presented and discussed in detail.The innovative spacer system is proven within this paper to add significant value to extreme cementingoperations by improving and maintaining impressive sealing capabilities and can reduce formationbreakdown and fallback of cement tops.The spacer comes along with advantages that include compatibilitywith various drilling fluids and cement.This spacer is environmentally friendly and applicable in bothvertical and horizontal wells.In addition,the spacer will form a seal to minimize filtrate invasion into theformation,effectively reduce loss circulation and enhance hole-cleaning prior to cement placement.