Proceedings of Meetings on Acoustics Volume 19, 2013 http://acousticalsociety.org/ ICA 2013 Montreal Montreal, Canada 2-7 June 2013 Engineering Acoustics Session 4pEAb: Fields and Devices 4pEAb3. Case studies of casing inspection with multi-functional ultrasonic imaging logging tool Zhifeng Sun*, Honghai Chen and Xien Liu *Corresponding author's address: China Oilfield Sevrices Limited, Beijing, 101149, Beijing, China, sunzf@cosl.com.cn The multi-functional ultrasonic imaging logging tool can provide casing inspection and cement bonding evaluation by using ultrasonic pulse echo technique. The casing's internal conditions can be inspected from echo amplitude and transit time curves. The casing thickness and the cement impedance can be calculated from resonance frequency and resonance decay. The paper describes three well cases histories of casing inspection in detail with this instrument. The first case reports the evaluation of perforation interval in the cased hole; hole enlargement of perforation interval and perforations can be seen from echo amplitude and casing internal radius imaging curves. In the second case, we can't distinguish corrosion or deposits in the casing thickness imaging curve, but the echo amplitude and transit time curves characterize some deposits in the casing surface. Finally, the last case history describes evaluation of casing mechanical wear in a deviated well; casing thickness imaging curve shows mechanical wear is caused by logging instrument in low side well. All cases shows that the multi-functional ultrasonic imaging logging tool can provide both quantitative and qualitative evaluation and diagnosis of casing problems. Published by the Acoustical Society of America through the American Institute of Physics 2013 Acoustical Society of America [DOI: 10.1121/1.4799239] Received 9 Jan 2013; published 2 Jun 2013 Proceedings of Meetings on Acoustics, Vol. 19, 030106 (2013) Page 1
INTRODUCTION Almost one hundred million yuan economic losses 1 are directly caused by casing corrosion in china's oil and gas exploration and production industry every year. And these losses do not include the cost arising from the leakage and the loss of profit. Therefore casing corrosion inspection can not only reduce the direct cost, but also can inspect weak point before the leakage of casing, so as to reduce the risk of safety and environment. Ultrasonic imaging well logging technology inspect casing corrosion through inner diameter, outer diameter and casing thickness by using ultrasonic pulse reflecting principle 2-3, meanwhile it has a unique technological advantage in cement bonding evaluation 4. Foreign oilfield service companies have already researched the instrument based on ultrasonic pulse reflecting method. Schlumberger developed USI instrument, which can inspect casing thickness and cement bonding by using high bandwidth ultrasonic transducer. Halliburton developed CAST-V instrument 5, which can inspect different type casings by different frequencies ultrasonic transducers. The new generation Isolation Scanner instrument 6 which was developed by Schlumberger, not only has the function of casing damage detection, but also can give quantitative evaluation of the first and second interface cement bonding quality. China Oilfield Services Limited developed independently MUIL 7-8 (Multi-functional Ultrasonic Imaging Logging Tool) instrument. This instrument can not only image in open hole, but also can make quantitative evaluation on casing thickness and cement bonding quality in cased-hole. In this paper, measurement data of three casing wells show that this instrument has ability in casing inspection. MEASUREMENT PRINCIPLE OF CASING INSPECTION The MUIL instrument' transducer sends an ultrasonic pulse signal, and then switches to receive mode. The ultrasonic pulse signal spreads through the fluid and then strikes the casing wall. Most of the energy is reflected back toward the transducer and is received. The remaining energy enters the casing and reflects many times between the casing and the cement ring surface and between the casing and formation surface. When casing thickness is equal to integral number of half a wavelength, ultrasonic resonance occurs in casing. The casing thickness can be evaluated by the resonance frequency of the casing and the compression wave velocity of propagation in casing. Figure 1 shows 60 measurement waveforms per scan at a certain depth. It shows that the reflection wave will be firstly received by transducer and then is the resonance wave. Although a centralizer must be used in the well logging, it still can't eliminate the eccentricity effect. As each waveform has a different transit time, eccentricity correction is essential for imaging curves in the data processing. Frequency spectrum curves of measurement waveforms are shown in the figure 2. The character of spectrum trap is obviously visible in frequency spectrum curve of waveform, and the amplitude of spectrum trap is different. As casing thickness and cement impedance are not exactly same in each direction per scan, each resonance frequency of spectrum curves corresponding to the spectrum trap are slightly different. FIGURE 1. Measurement waveforms per scan FIGURE 2. Frequency spectrum curves of waveforms Proceedings of Meetings on Acoustics, Vol. 19, 030106 (2013) Page 2
Sun et al. CASES ANALYSIS OF CASING CORROSION EVALUATION First Case History-Perforation Inspection This case history focuses application effect of the MUIL instrument in the perforated zone of casing well in the Arab Emirates. The casing size is 7 in, 29 lb/ft, 6.18 in casing inside diameter, 0.408 in casing thickness. This well was perforated vertically in the depth of 2668m~2674m, 2683m~2688m, 2691m~2697m sections. There are 14 perforations in every meter. Figure 3 shows result of casing corrosion evaluation for the first case history. Imaging curves have obvious responses in the three perforated zones. As seen in transit time image map and internal radius image map, the inner diameter becomes larger due to perforating gun's pressure to casing, and the transit time of refection wave arrive late. The casing thickness curves have no obvious change, so perforation did not produce apparent effect to the casing. In order to observe perforations response in the map, the scale of echo amplitude map enlarged 1:20, the result as shown in the right figure. The vertically aligned perforations can be clearly observed in the echo amplitude map. Proceedings of Meetings on Acoustics, Vol. 19, 030106 (2013) Page 3
Sun et al. FIGURE 3. Result of casing corrosion evaluation for the first case history Second Case History-Contamination Detection in Casing Surface This case history focuses application effect of the MUIL instrument in the contaminative casing well in China Bohai. The casing size is 9-5/8 in, 47 lb/ft, 8.681 in casing inside diameter, 11.99 mm casing thickness. Figure 4 shows result of casing corrosion evaluation for the second case history. As seen in the casing thickness curves, the average casing thickness is about 11.7 mm and the maximum casing thickness curve and the minimum casing thickness are almost equal to the casing standard thickness, it s no damage in the casing. But the echo amplitude map and the transit time map have some responses on the inner surface of the casing. We can infer that there may be some scaling or contamination in casing surface, which decreases the echo amplitude. FIGURE 4. Result of casing corrosion evaluation for the second case history Proceedings of Meetings on Acoustics, Vol. 19, 030106 (2013) Page 4
Third Case History-Casing Corrosion Inspection This case history focuses application effect of the MUIL instrument in the corrosive casing well in China Nanhai. The borehole deviation is about 12 degrees below the depth of 1783m. The casing size is 9-5/8 in, 40 lb/ft, 8.835 in casing inside diameter, 10.03 mm casing thickness. Figure 5 shows result of casing corrosion evaluation for the third case history. The orientation of imaging maps is corrected in borehole high side. From the echo amplitude map and the transit time map, we can see that this casing has some corrosion in the borehole low side in the whole depth. As seen in the casing thickness curves, whole section has corrosion which locate at about 60 degree angle in the circumferential direction. And the measurement minimum casing thickness is equal to 6mm. So casing corrosion almost reaches 40%. As the logging instruments make perennially effect of mechanical wear to borehole low side, the casing damage is greatest in casing low side, whereas there is almost no casing damage in the other circumferential direction. FIGURE 5. Result of casing corrosion evaluation for the third case history Proceedings of Meetings on Acoustics, Vol. 19, 030106 (2013) Page 5
CONCLUSION This paper shows the ability of casing inspection with MUIL instrument by using three cases history. We can judge the casing' scaling or contamination, image perforations in the perforated zone and make quantitative evaluation of casing corrosion through echo amplitude map, transit time map, internal radius image map, casing thickness map and other information. All the examples have demonstrated that scanner images can help repair well leakage for better well results and longer well life. ACKNOWLEDGMENTS The work was supported by the National Key Projects (No. 2011ZX05020-005) and the National High Technology Research and Development Program of China (No. SQ2010AA0920229001). REFERENCES 1. Yin Z M, Wu Q, Liu J J, et a1., Numerical simulation on effect of pressure relief of water injection well on casing squeeze pressure, Chinese Journal of Rock Mechanics and Engineering. 23(14), 2390 2395 (2004). 2. Yan X, Wang H, Hu W X, Numerical simulation of interface detection in layered media using ultrasonic method, Technical Acoustic. 26(5),83 84 (2007). 3. Che X H, Qiao W X, Measuring thickness of cylindrical tubes with spectra of ultrasonic pulse echoes, Technical Acoustic. 22(1),14 29(2003). 4. Ding Y, Qiao W X, Che X H, The influence of cementing acoustic impedance on the ultrasonic pulse reflection waves, Well Logging Technology. 35(1):55 57(2011). 5. Batakrishna Mandal and Alberto Quintero, A new monocable circumferential acoustic scanner tool(cast-m) for cased-hole and openhole applications, Perth, Western Australia, June 19 23, 2010 SPWLA 51st Annual Logging Symposium. 6. C. Morris., L. Sabbagh., Application of enhanced ultrasonic measurements for cement and casing evaluation, Amsterdam, Netherlands, February 20 22, 2007 SPE/IADC Drilling Conference. 7. Sun Zhifeng, Qiu Ao, Wang Wenliang, et a1., Design of multi-functional ultrasonic imaging logging tool, Hongkong, May 13 18, Acoustic 2012 HONG KONG Conference and Exhibition. 8. Chen H H, Sun Z F, Wang W L, et al,. Model experiments on casing inspection with the multi-functional ultrasonic imaging logging tool, Well Logging Technology. 36(4):341 344(2012). Proceedings of Meetings on Acoustics, Vol. 19, 030106 (2013) Page 6