Well Integrity Services
Built from thousands of feet of casing and tons of cement, comprehensive cased-hole well integrity raises questions that no single tool or measurement can answer. Left unchecked, even tiny leaks can cascade from lost production to environmental damage, which can lead to downtime, extensive repairs, and regulatory penalties.
Our SecureView® cased-hole diagnostic service brings clarity to your cased-hole problems by giving them a name, location, and a path to remediation. By making the single-trip SecureView service a regular part of your well maintenance schedule, you get a definitive and high-resolution view of cement and casing integrity.
High Resolution Real-Time Thickness Measurement of Internal and External Casing Anomalies with Ultrasonic Scanner Tools
Lucio N. Tello, Dimas C. Azuaje, and Dung Tran, Weatherford
The internal and external casing condition is an important part of well integrity evaluation. The public is concerned with environmental issues at sea and on land. In areas where shale exploitation is in full swing, the protection of the underground aquifers is of concern. Tools with increased resolution in corrosion and thickness evaluation are being upgraded to meet these challenges. Ultrasonic scanning tools measure casing thickness by inducing a resonance in the casing in the thickness-mode. At the same time, they measure the cement acoustic impedance at higher radial and vertical resolution than standard CBL and sector tools. Traditionally, the thickness measurement is delivered after computing the resonant frequency of the pipe from the raw waveforms telemetered to the surface via the communication system. This method is fine except there is a time delay between the acquisition and the final delivered thickness log and map. Another disadvantage of this method is that to cover the pipe circumference for thickness, the logging speed needs to be reduced during acquisition. A modified Digital Fourier Transform algorithm implemented in the ultrasonic radial scanner tool improves the circumferential and vertical coverage over previous methods while extending the thickness measurement range, resolution, and accuracy. External corrosion is evaluated by ultrasonically measuring the pipe ID and adding it to the thickness. The algorithm is performed by the downhole tool at high speed and resolution, covering the pipe in both circumferential and vertical dimensions, in real time and at normal logging speeds, thus saving operation and rig time. Log examples from test wells constructed to simulate internal and external corrosion, as well as results from field testing, corroborate the methodology and the algorithm. The ultrasonic radial scanner with real-time thickness (RTT) capability gives a higher resolution thickness measurement and an improved internal and external corrosion evaluation.
Casing Wear Prediction and Management in Deepwater Wells
William Malcolm Calhoun, Sheldon Perry Langdon, and Jiang Wu, Chevron; Gerald Phillip Hogan and Kory Rutledge, Weatherford
Deepwater Gulf of Mexico wells are generally deep and they may incorporate casing designs that provide only a single-casing barrier between the wellbore and the formation. These aspects present unique issues and risks in regard to casing wear. The extreme depths (>30,000 ft) of many wells in the Gulf of Mexico create the potential for high side loads imparted by the drillstring to the casing, even with low doglegs (1.0°/100 ft or less) in the upper part of the well. This, combined with potentially high rotating hours, particularly on exploration wells with sidetracks, creates the potential for casing wear that exceeds allowable limits. In order to proactively manage and mitigate casing wear during drilling operations, Chevron has developed a Casing Wear Monitoring standard operating practice (SOP). Deployment and application of this SOP has proven effective. Application of this SOP indicates that casing wear can be predicted, managed, and/or mitigated with proper planning and execution. This paper illustrates a casing wear event on a Chevron well and provides an overview of the Chevron Deepwater Casing Wear Monitoring SOP. Additionally, the paper highlights some casing wear processes, well control issues, and environmental risks that are unique to deepwater wells. Application of the casing wear prediction and monitoring procedures outlined in this paper help to ensure that the integrity of the casing is maintained during drilling operations, thereby reducing the risk of a health, safety, and environment event or loss of the well due to excessive casing wear.
Improving the Accuracy of Cement Bond Evaluation by Improving the Borehole Fluid Impedance Measurement in Ultrasonic Scanner Tools
Ultrasonic scanning tools measure the cement acoustic impedance at higher radial and vertical resolution than radial cement bond and sector tools. The cement impedance measurement is affected by variations of the borehole fluid contained in the well. Until now, ultrasonic tools estimated the value of the fluid impedance by measuring the slowness and multiplying this value by the density, which is a constant reading at the surface. Occasionally, the slowness measurement is acquired during a logging down pass. An error is introduced when the fluid changes from one type to another, because both slowness and density change with the fluid; however, density will change in larger percentages than slowness. This causes the estimated fluid impedance to have a substantially different value than the actual one. Not surprisingly, this difference in fluid impedance causes the cement evaluation to differ as well. In this paper we present the results of the field testing program of the newly developed mud chamber for the ultrasonic radial scanner tool. Instead of calculating the impedance indirectly from the slowness measurement, the mud chamber measures the fluid impedance directly. The tool takes this measurement in situ, during logging, and with greater accuracy than before. In addition, we present the algorithm that computes changes in the cement impedance which are due to variations of the impedance in the fluid column. Observations in laboratory tests and logs obtained during field testing show that the fluid column commonly has variations in the acoustic impedance and its density. Under the new measurement, phantom communicating channels are not displayed and actual channels are correctly detected. The effect is accentuated in instances where stratigraphic fluid columns with different densities are present. The new mud chamber eliminates the uncertainties of small channels by detecting the presence or absence of cement.
High Resolution Casing Imaging Utilizing Magnetic Flux Leakage Measurements
Munir Ahmed Sharar, David Andrew Cuthill, and Ken Edwards, Weatherford Canada Partnership
Magnetic flux leakage (MFL) logging tools work on the principle of inducing a magnetic flux within the casing wall and observing the amount of MFL due to variations in the casing thickness. Commonly, these devices utilize coil type sensors to measure the flux leakage and an electromagnet to induce the magnetic field within the pipe wall. Coil type sensors have an inherent limitation requiring the logging tool to move at a fixed logging speed in order to provide a meaningful measurement of flux leakage. Furthermore, the use of electromagnets to induce the magnetic field requires that the magnet be powered from surface, which also has intrinsic problems with power limitations and variation in the field strength. A new generation of logging tool has been developed that utilizes a powerful samarium cobalt (SmCo5) permanent magnet to induce a high magnetic flux within the casing wall and Hall-effect sensors to detect perturbations in the internal surface flux caused by outer or inner defects in the pipe. Hall-effect sensors do not require a consistent logging speed in order to accurately measure flux leakage. The combination of these two developments now enables defects to be located in areas such as near surface where previous logging speed dependent methods would not work. An advanced interpretation method has also been developed that uses 3-dimensional images generated from high resolution MFL measurements. This type of measurement provides a clearer picture of the defects within the joint and also the ability to visually analyze and classify the MFL associated with collars and other hardware. Collars and hardware are commonly ignored when using traditional interpretation methods. Several examples are presented that demonstrate the improvements in logging tool functionality and in the use of 3-dimensional visualization techniques, most notably close to surface and near casing collars.
Ultrasonic High Resolution Real Time Thickness Combined With High Resolution Multi-Sensor Caliper and CBL Tools in a Single Pass: New Mechanical Well Integrity Logging String Identifies Difficult Casing Problems
Lucio N. Tello, Eglee Y. Lopez, and Dimas C. Azuaje, Weatherford
Ultrasonic scanning tools measure the casing thickness by inducing a mechanical resonance of the casing in the thickness mode. At the same time they measure the cement acoustic impedance at higher radial and vertical resolution than sector and segmented tools. A modified multisensor caliper tool measures the casing ID with excellent accuracy and resolution. A DFT algorithm implemented in the ultrasonic radial scanner tool improves the circumferential and vertical coverage of the thickness over previous methods while widening the measurement range, resolution, and accuracy. The algorithm is performed by the tool with more circumferential coverage of the pipe than before. The tool performs this in real time at normal logging speed, thus saving operation and rig time. When the new ultrasonic radial scanner tool is combined with the new multisensor caliper, the magnetic flux-leakage tool, and the CBL in one pass, the tool string generates data that identifies casing damage otherwise difficult to detect with just one of the tools. In addition, the ultrasonic cement impedance measurement and the CBL-VDL (in combination) identify clearly the cement bond conditions. This combination provides comprehensive well mechanical integrity interpretation of the well. New 3D visualization capabilities of caliper, magnetic flux-leakage, and ultrasonic measurements provide the operator with information to interpret broken or parted casing. This 3D visualization also provides critical information after the remedial work is finished. Discerning whether there is internal or external damage is important information for the operator. The capability to identify previously undetected casing damage corroborates the new high-resolution real-time thickness methodology and the improved multisensor internal caliper measurements. The four tools in combination provide a valuable method for identifying difficult casing problems.
The Fourier Transform Applied To Cased-Hole Ultrasonic Scanner Measurements
Lucio N. Tello, Sarah D. Molder, and Richard M. Holland, Weatherford
Ultrasonic radial scanner tools provide data to evaluate well cement and casing condition. Specific measurements of interest include internal and external casing diameter, casing thickness, and the acoustic impedance of the material behind casing. Often, the main challenge for an ultrasonic radial scanner tool is to distinguish between different materials behind the casing with the same impedance reading: foam cement, light cement, or heavy drilling fluids. Because all measurements taken by ultrasonic radial scanner tools are interrelated, it is important to view all individual measurements and get a complete picture before stating problems with casing or cement. Physical changes inside or outside casing diameter, the thickness of the casing, and even the method of casing manufacturing will cause the cement impedance to read incorrectly. Described here is the development of three new fast Fourier trails form algorithms that accurately evaluate the acoustic impedance of all cement slurries. The first transform is pan of a unique automatic-calibration process performed by the ultrasonic radial scanner tool to reduce the effect of the casing on the cement acoustic impedance readings. The second transform is used to distinguish between foam cement and other cement types or heavy drilling fluids. The third transform is used in the calculation of the casing thickness, and when used in combination with the internal radius information, results in identification of the external pipe condition. Excellent results have been obtained using data acquired during logging operations for cement acoustic impedance evaluation. In this paper we present a series of cased-hole log examples displaying pipe thickness, foam cement evaluation, and the novel tool self-calibration, all using algorithms with particular re-incarnations of the fast Fourier transform.
Let’s shine a light on cased-hole well integrity.
Our technology helps you prevent complex problems tomorrow by uncovering the smallest of threats today. The efficient SecureView system provides clear, high-definition logs of your inner casing, outer casing, cement strength, and cement bond.
The SecureView cased-hole diagnostic service is the only comprehensive, single-trip casing and cement evaluation in the industry.
Our technology is comprised of a suite of well-diagnostic technologies that combine and overlap measurements to detect any wellbore problem quickly and efficiently.
The SecureView service uses a suite of technologies—UltraView™, CalView®, FluxView®, and BondView™ tools—to deliver a clear casing and cement diagnostic with minimal logging downtime.
The four SecureView tools can run in combination to gather comprehensive data without information gaps. By overlapping some measurement capabilities, these tools provide clear, conclusive well-integrity data that gives you a map to the most efficient remediation.