Executive Summary

Robert Mitchell, Halliburton Company

Wellbore Stability and Wellbore Fluids

The two central topics for this issue of SPE Drilling &Completion journal are the two intimately related topics of wellborestability and fluids used in the wellbore, either during drilling or forcompletion design and installation. Several papers directly address the topicof wellbore stability: a new, more comprehensive fracture model is proposed,methods for strengthening wellbores through propping fractures are studied,perforation plugging by produced formation particles is studied, andsand-control failure issues are discussed. Wellbore issues directly influence anumber of fluid-design issues: a new cement is formulated to minimize formationhydrate decomposition, water-based muds are designed to prevent shale swelling,a comprehensive discussion of well-fluid choice in a major project ispresented, and drill-in fluids to clean the formation are developed. Wellborefluid even has an impact on tubing cutting.

If your interests focus on wellbore stability and fluid interaction, thenthis issue is for you. There are 14 papers in this issue. The following gives abrief overview of each paper.

Current State of the Premium Screen Industry: Buyer Beware, MethodicalTesting and Qualification Shows You Don’t Always Get What You Paid For.Recent catastrophic sand-exclusion failures have led some operators andindependent laboratories to perform additional testing and quality controlchecks. This paper describes a process to select sand-exclusion products byqualifying an individual product design, including retention media, metallurgy,subcomponents, manufacturing process, and the final assembled product.Cement-Slurry Design To Prevent Destabilization of Hydrates in DeepwaterEnvironment. There is a compelling need to prevent destabilization ofhydrates. The volume of cement results in a great amount of heat generatedduring setting, and the production of hydrocarbons increase the temperature ofthe formation. Cement slurries have been designed to lower the heat ofhydration, and the improved cement-slurry designs lower considerably thethermal conductivity of the set cement sheath. Effect of Well Variables onthe Performance of Chemical, Jet, and RCT Tubing Cutters  . Ananalysis of 72 tubing cuts in the Gulf of Mexico was completed to determine theeffect of well variables on the cutting performance of chemical, jet, andradial cutting torch cutters. It was determined that chemical cutter success inCaBr2 completions fluids was much lower than all other fluidscombined, and that placing the pipe in tension significantly increased cuttingperformance. Designing Well Fluids for the Ormen Lange Gas Project, Right onthe Edge. Because of environmental constraints and the selected sandfacecompletion type, a water-based fluid system was required in developing theOrmen Lange field. The knowledge gained in the laboratory testing phase wastransferred to the field. The first three wells of the initial developmentphase have been drilled and completed trouble-free, and the resultingproduction rates have met expected targets. Wellbore-Stability Performanceof Water-Based Mud Additives. A critical property for many water-based mudsis the ability to prevent near-wellbore pore pressure increase in shales, whichpromotes wellbore stability. All muds tested slowed the loss of overbalancepressure compared to a base-case brine fluid, but two muds were very effectiveat slowing and/or preventing the loss of overbalance. Measurements offluid-induced swelling were also conducted in this same set of tests, and allfour muds resulted in less swelling than the base-case brine. CorrelatingFlowing Time and Condition For Perforation Plugging By Suspended Particles.Accurate correlations were developed for the effect of pore throat toparticle-size ratio on flowing fluid conditions and plugging time leading toparticle bridging. Such empirical correlations can be used to determine andalleviate the conditions that induce perforation and pore plugging by migratingparticles in petroleum reservoirs. Use of Ester as a Precursor to CleanFormate Drill-In Fluid Damage in Horizontal Wells. Formate-based brineshave been used in drilling and completion operations for more than 10 years.Filter cakes that are generated by drilling fluids can act as a barrier to thefluid flow, and the conventional method for cleaning filter cake is by usingsolids-free formate brines. A new precursor ester generated an acid downhole ata low release rate, which results in uniform fluid distribution through thewellbore. This ester solution was more effective in cleaning the filter cake incomparison to the formate brines. Treatment of Hydrocarbon-Based DrillingWaste Using Supercritical Carbon Dioxide. Nonaqueous drilling fluids areessential in challenging drill operations, but they require special treatmentand disposal because of their potential for environmental damage. In thispaper, the results of a study using supercritical carbon dioxide to treatsynthetic-based drilling waste are presented. Optimization of the process hasyielded efficiencies as high as 97%. Further, the results suggest that thecollected hydrocarbons may be reused in the drilling process, resulting insignificant cost savings to the industry. Continuous Improvement in Slop-MudTreatment Technology. Development of an understanding of the slop mudstream enabled a novel continuous treatment system to be built, which providesefficient and fast phase separation with recovery of the valuable drillingfluid phase, with significant advantages over current batch-type systems.Modeling Air and Water Perforator Swell for Better Risk Management. Adetonated, shaped charge fired from a perforating string or perforating gunwill not only perforate its targets but also possibly cause excessive damage orswell to its carrier. A method based on energy conservation is used toestablish a swell model to predict the post-detonation conditions of theperforator, and a criterion is proposed to establish the serviceability of theperforators. Microwave Treatment of Oil-Contaminated Drill Cuttings at PilotScale. In the North Sea, there is a 1% residual oil limit for dischargedcuttings. A thermo-mechanical cuttings cleaning process has produced cuttingswith oil <1%, although with a significant deck-space impact and restrictedthroughput. Previous studies have shown that microwave treatment is able toreduce oil levels to well below 1% in a laboratory environment, and this workhas studied the scaleup of the system to a 500 kg/hr continuous process. ANovel Technique for Determining Sand Screen Failure. Properly designed andexecuted sand-control completions are still subject to mechanical failure, withthe first indications often being the production of solids into a commonseparation facility, where it is often difficult and expensive to determinewhich well or specific completion interval has failed. To solve thisidentification problem, a new proppant/gravel has been developed and taggedwith over 20 unique markers that provide the ability to identify the exact wellor zone that has failed. Investigation of Factors for Strengthening aWellbore by Propping Fractures. Wellbore strengthening or stress cageimplementation has been recognized as an effective means of dealing with lostcirculation. However, a good understanding of this mechanism is necessary toavoid a potentially flawed design and implementation process that couldadversely affect job success in the field. This paper describes those factorsthat are important in designing wellbore strengthening jobs and addresses theconditions necessary to ensure fracture stability. A New Fracture Model ThatIncludes Load History, Temperature, and Poisson's Effects. A model forfracture initiation is presented, based on the classical Kirsch equation, butincluding the Poisson’s effects that arise when the borehole is pressurizedfrom one stress state to another. As opposed to the classical Kirsch model, thenew model starts with the initial in-situ stress and the virgin in-situtemperature. The mechanical and thermal loading towards fracturing is,therefore, modeled from this initial state.