Schlumberger

Technical Paper: Ultrasonic Cement Logging—Expanding the Operating Envelope and Efficiency

Society: SPWLA
Paper Number: SPWLA-2017-WWWW
Presentation Date: 2017
 

Abstract

In this paper, we present new ultrasonic cement evaluation technology developed and extensively field tested over the past years. The introduction of this technology increases reliability and efficiency, and enables well integrity inspection in extreme environments with heavy muds and very large and thick casings. Such extreme conditions with heavy synthetic oil-based muds up to 20 lbm/gal and casing thicknesses up to and above 1 in. are often encountered when dealing with wells in deep water, wells used for carbon sequestration and underground gas storage, and shale oil and gas wells subject to hydraulic fracturing. Conventional ultrasonic cement evaluation technology has not been able to properly assess these cases in the past.

We have addressed these challenges through new ultrasonic transducer technology with a thirtyfold increase in performance and an extended bandwidth that make it possible to log in the heaviest and most attenuative mud environments and through thick-walled casings. We have developed a calibration-free ultrasound pulse-echo processing method that capitalizes on self-compensation for mud properties and eliminates the need for separate mud property measurements. We have revised the electronics and embedded software to enable increasing the ultrasonic firing and acquisition rates leading to a threefold increase in logging speed. Finally, operating workflows have been revised to support both faster wellsite turnaround time, and robustness and the reliability of wellsite answers. This standard workflow with downhole normalizations, real-time quality control plots, and quick interactive previews provide the highest possible data quality at the wellsite.

We present examples from our extensive field test campaign to demonstrate the capabilities of these new ultrasonic pulse-echo and flexural wave measurement developments. We describe how they enable cement evaluation and pipe inspection in environments of heaviest muds and large diameter/wall-thickness casings, and we show that these developments augment the ability to carry out well integrity diagnosis and help reduce uncertainty and risk in well construction or during plugging and abandonment (P&A).

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