Ultrasonic probes
Elastomer element
Drip pan
These measurements help users optimize string life and reduce tube failures in the fi eld. The CT InSpec device does not address all CT inspection issues, but is a significant step forward. Combining this technology with existing magnetic-flux leakage or ultrasonic shear measurements may allow detection of localized fl aws, such as pitting and corrosion. In addition to improved CT string management, new developments are optimizing wellbore cleanout operations.
Wellbore Remediation
About 50% of CT operations involve removing for- mation sand, fracturing proppants or other solids from wells (next page, top). These materials limit or prevent production, block the passage of wireline or other downhole tools, and interfere with completion and well-intervention opera- tions. Conventional CT techniques often leave solids behind, requiring repeated cleanout attempts over an extended period, which increase costs and delay production. To address this problem, Schlumberger conducted extensive testing directed at under- standing solids transport by cleanout fl uids.7
The
> Coiled tubing inspection. Improved pipe inspection helps reduce tube failures and optimize pipe life. The CT InSpec wellsite system uses 12 ultrasonic probes, arranged radially, to monitor wall thickness and pipe ovality over variable CT interval lengths (top). This new device measures tubing wall thickness as coiled tubing comes off the reel (bottom).
Tube materials, manufacturing processes and quality control before coiled tubing goes to the field have improved through an alliance with CT supplier Precision Tube Technology Inc. The CoilLIFE coiled tubing life prediction model helps assess fatigue damage and remove coiled tubing from service before it reaches the end of its useful life. The PipeSAVER coiled tubing storage inhibi-
tion system has improved coiled tubing handling by mitigating mechanical damage and corrosion. Training personnel in the proper use and mainte- nance of the pipe, and planning tools, such as CoilSAFE coiled tubing risk assessment system, help address operational safety. The Schlumberger global tubing inventory has aided in understanding coiled tubing performance by requiring that fail- ures be recorded, analyzed and categorized. Fracturing and acid stimulation through
coiled tubing erode or corrode the steel. Certain well environments, such as chrome tubulars, cause external coiled tubing abrasion, and CT is
being used at higher pressures, with the defi ni- tion of “ high-pressure” constantly increasing. These increased demands require a better means of monitoring CT integrity.
Several CT inspection systems have been developed. The universal tubing integrity moni- tor (UTIM) measures tube diameter and ovality. Other systems that detect cracks and pits, and give an average wall thickness have niche appli- cations, but none are completely satisfactory. These limitations drive ongoing research and development in CT inspection. Technology is currently being developed to
address fl aw identifi cation and description, the effects of flaws on coiled tubing life, and assessment of related risks. The new ultrasonic CT InSpec real-time device, for example, moni- tors both ovality and wall thickness (above).6 Wall thickness is directly related to tubular burst strength, remaining string life, string abrasion and erosion effects and critical load-conveyance effects.
resulting PowerCLEAN engineered fill removal service is an integrated approach that consists of specialized fluids, improved jetting nozzles, design software and a real-time system that monitors returning solids at the surface (next page, bottom).
Mixed with fresh water or seawater, PowerCLEAN fluids create a low-friction, high- viscosity stable solution that extends cleanout effectiveness to 325° F [163° C]. Water, guar, hydroxyethyl cellulose (HEC), xanthan and viscoelastic surfactants (VES) can also be used with the PowerCLEAN system up to their temperature limit— about 250° F [121° C]. Previous CT nozzle designs commonly have forward-only or forward and backward jets that do not effectively remove solids from high-angle wells. New PowerCLEAN nozzles have no moving parts, but create a swirling effect that provides continuous jetting; this utilizes fl uid energy more efficiently and removes solids at greater than twice the rate of conventional nozzles. The PowerCLEAN software integrates cleanout simulation with job optimization. Job parameters include circulating rate, CT running
6. Newman KR and Lovell J: “ A New Approach to Ultrasonic CT Inspection,” paper SPE 87122, presented at the SPE/ICoTA Coiled Tubing Conference and Exhibition, Houston, Texas, USA, April 8– 9, 2003.
7. Rolovic R, Weng X, Hill S, Robinson G, Zemlak K and Najafov J: “ An Intergrated System Approach to Wellbore Cleanouts with Coiled Tubing,” paper SPE 89333, presented at the SPE/ICoTA Coiled Tubing Conference and Exhibition, Houston, Texas, USA, March 23– 24, 2004.
44 Oilfi eld Review
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