Case History: Internally Coated Completion Workstring Successes

Abstract

Completion workstrings must endure an extremely hostile environment of erosive and corrosive fluids. Today's improved internal plastic coatings can protect the significant investment in drill pipe from erosion/corrosion, as well as minimize completion trouble time caused by pipe debris (scale). An internally coated, Class 2 drill string was used for 2 1/2 years to successfully Frac Pack seventeen, high productivity, Gulf of Mexico Deepwater completions in the Genesis Field. More than 2,000,000 pounds of abrasive proppant was pumped without a pipe failure. Introduction The completion workstring requirements were reviewed during the development well planning for the project in 1998. During completion processes, this pipe would be subjected to only minimal tensile stress and torsion; however, the pipe would need to bear the rigors of numerous Frac Pack completions. The plan originally included 22 Frac Pack completions from 16 wells with anticipated surface treating pressure of up to 10,000 psi (depending on the selected completion string diameter). The planned wells ranged in depth from 12,000' to 23,000' and in hole angle from 16° to 66°. During each completion, the 6 5/8" drill string would be changed to a smaller diameter completion workstring to displace the well to CaCl2/CaBr2 completion fluid, tubing conveyed perforate (TCP) underbalance, pressure surge the perforations, wash sand fill, and Frac Pack. The workstring would then be sent to a pipe yard to be stored outdoors until the next completion operation occurred in roughly one month. After reviewing the alternatives, the rig contractor's 5", 19.50#/ft, S-135, 4 1/2" IF drill pipe was selected for the completion string. This workstring was a collection of used pipe with an RP7G API-IADC Used Drill Pipe Classification System rating of Class 2 due to undersized tool joints.1 Some of this pipe was as old as 20 years yet the tubes met Premium Class standards with 80% wall thickness (0.290") remaining. Premium Class tubes have a tensile rating at minimal yield strength of 560,764 lbs and an internal yield pressure rating at minimum yield strength of 15,638 psi. The reduction in torsional strength due to the reduced tool joint diameter was not a concern due to minimal rotation for drilling cement anticipated. These specifications met the anticipated completion workstring requirements and the rig contractor was pleased to find commercial use for this drill pipe rather than scrap it for roughly $50 per joint or replace the tool joints for roughly $700 per set. An abrasion resistant internal drill pipe coating was considered to combat further internal wall loss due to proppant laden Frac Packs. A wall loss of only 0.036" could downrate the Premium Class tubes to Class 3 (<70% wall) which has no RP7G published rating for tensile forces or internal yield pressure. The drill pipe would then be scrap pipe. Additionally, the internal coating should minimize internal pipe rust and eliminate the need for acid pickle treatments. For deepwater operations, acid pickle treatments cost roughly $10,000 for purchase, transportation, rig time, and disposal. Most importantly, using an internal coating would eliminate the safety, environmental, and liability risks associated with handling and disposing of acid. A liquid-applied, modified epoxy-phenolic internal coating specifically formulated for drilling environments was considered for the completion program. Standard industry tests for coating abrasion resistance (Taber Abraser test, ASTM #D 4060) measure a test sample's weight loss in mg over 1000 cycles of abrasion using a CS-17 wheel with a 1000 gm load.2 In 1998, the coating considered for use had results, provided by the supplier, of 47 mg of coating lost / 1000 cycles. A bare steel plate was tested to determine the weight loss without a coating; surprisingly, the results were similar (45 mg of metal lost / 1000 cycles). Taber Abraser test information, although useful to compare coatings, does not answer the question of whether a coating will survive repetitive Frac Pack treatments.

Deepwater Extended-Reach Sand-Control Completions and Interventions

“…Documented benefits of using internal drillpipe coatings during the Genesis field completions include reduction of hydraulic friction pressure, pipe-scale debris minimization, and extended drillpipe life (Pourciau 2002). All these benefits were realized during the Petronius extended-reach program: no pump-rate problems during the displacement or frac pack, no internal pipe scale, and no drillpipe failures.…”

“…All these benefits were realized during the Petronius extended-reach program: no pump-rate problems during the displacement or frac pack, no internal pipe scale, and no drillpipe failures. It should be noted that the Genesis paper (Pourciau 2002) documents a 16% higher pump rate at a given pump pressure, or a 25% lower pump pressure at a given pump rate using 16,000 ft of drillpipe, because of the lower hydraulic friction of internally coated drillpipe as compared to bare pipe. The Petronius extended-reach completions used significantly more drillpipe (sometimes double the amount used in the Genesis field), and the hydraulic effect should therefore be proportionally greater.…”

Designing and Implementing Deepwater Extended-Reach Sand-Control Initial Completions and Interventions

“…Documented benefits of using internal drill pipe coatings during the Genesis Field completions include hydraulic friction pressure reduction, pipe scale debris minimization, and extended drill pipe life. 5 All these benefits were realized during the Petronius extended reach program: no pump rate problems during the displacement or frac-pack, no internal pipe scale, and no drill pipe failures. It should be noted that the Genesis paper documents 16% more pump rate at a given pump pressure or 25% less pump pressure at a given pump rate using 16,000-ft of drill pipe due to the lower hydraulic friction from internally coated drill pipe (as compared to bare pipe).…”

Improving Wellbore And Formation Cleaning Efficiencies With Environmental Solvents And Pickling Solutions

“…This was in addition to the elimination of safety, environmental and liability risks associated with handling and disposing of the returned pickle acid. 38 This method does not specifically address the issue of pipe dope residues.…”