Keep it clean

Halliburton’s Alan Marr examines how fluid advances can enable more efficient well clean-outs.

An example of a successful displacement is recognized by bright, clean pipes indicating clean casing and fluid. Photo from Halliburton.

Wellbore cleaning is crucial for maximizing the productivity and life of a well. Successful displacements should avoid non-productive time, minimize waste disposal, prevent formation damage due to residual solids, and allow completion equipment to be run safely. Residual oil and solids left behind by drilling operations can accumulate in drilling equipment, hindering completion operations and can also damage the producing formation. In the transition from drilling to completion operations, the wellbore is cleaned out and the drilling fluid is displaced with clean brine. A badly designed or poorly executed displacement can consume additional fluids, logistics and rig resources. Identifying the right technologies and processes can help complete wells effectively.

Recently, an operator achieved perfect displacement despite restricted pump rate. On an offshore platform well, pump rates were restricted during the cased-hole displacement due to the transfer restriction from rig to supply vessel. On a previous clean-out operation in which Halliburton was not involved, effective well clean-out was not achieved. The operator had to pull the completion and conduct a secondary cleanup. The end goal was to displace ENVIROMUL oil-based fluid to 10.0ppg sodium chloride brine with less than 0.05% solids and no visible oil.

As a result of lab testing, Halliburton Baroid’s BaraKlean-648 surfactant-based casing cleaner was selected for the job due to its strong solvent action and high cleaning capacity at lower annular velocities. BaraKlean-648 casing cleaner is a blend of surfactants and solvents used in fluid displacement and cleanup operations. The casing cleaner has strong cleaning and wetting actions to break and disperse mud film and residue. It is soluble in all common brines and is designed for the removal of a range of water, oil and synthetic based fluids.

The fluid cleaner was ideally suited to the technical constraints presented by this application. It also received the CHARM Gold rating, a widely accepted environmental classification and rating.

The displacement design was optimized using Baroid’s Completion Fluids Graphic (CFG) proprietary software package, which simulates the effects of critical parameters such as pump rates, circulating pressures, and annular velocities. Displacement simulation had not been conducted in the initial cleanup operation.

The challenges presented by the low pump rates and restricted pit space were overcome by careful planning, preparation, and execution of the operation. The wellbore cleanup operation was executed as planned, and the target cleanliness standards were achieved after minimum over-displacement.

The drillpipe and all components of the string were found to be clean when the assembly was pulled to the surface. The design and execution of the displacement using BaraKlean-648 cleaner provided an efficient displacement and created clearly identifiable interfaces that maximized mud recovery and minimized over-displacement. Brine usage was reduced, while rig time and waste disposal were minimized. As a result, this equated to an estimated savings of three days of rig rate, as there was no requirement to conduct a secondary cleanup operation and to rerun the completion.

The design and execution of a successful wellbore cleanup depends on an effective combination of chemistry, engineering and field practice. Employing a customized design process for engineered displacements, powerful cleaning solutions and optimization using software modeling is critical to that success.

Alan Marr is currently global product manager for completion fluids with Halliburton’s Baroid business line, based in Aberdeen, UK. Alan joined the oil industry over 10 years ago having previously worked for a pharmaceutical company. Alan’s experience includes laboratory work, field operations and technical services. He is a member of the Society of Petroleum Engineers and NACE International. Alan holds degrees in chemistry and oil and gas engineering.