Assessment of Foamed – Cement Slurries Using Conventional Cement Evaluation Logs and Improved Interpretation Methods

Abstract

Methods to evaluate conventional cements with logging data may not yield valid results in foamed cements. Logging tools commonly used in cement evaluation are the traditional cement bond log (CBL) tools and the modern ultrasonic scanning tools. CBL tools provide waveform images and acoustic amplitudes that together help describe cement-to-pipe and cement-to-formation bonding. Ultrasonic scanning tools contribute circumferential images and detailed information regarding the cement-to-pipe bond. The major problem in evaluating foamed cements is that their impedance values can be below that of annular fluids, such as mud or water. Thus, a standard interpretation of ultrasonic images and data in foamed cements may provide an incorrect diagnosis of the cement bond and could lead to unnecessary remedial cementing activities. A new interpretation method expands and improves on previously published methods to effectively evaluate foamed cements with the common cement-evaluation tools. This method uses ultrasonic scanning data to provide detailed information regarding the cement-to-pipe bond and allows foamed cement to be distinguished from mud or spacer fluid behind casing. Cement-slurry weight and composition do not affect this technique. The technique does not require additional logging tools or passes and thus does not introduce additional logging or rig expenses. Examples are presented showing that the new method is valid and is effective in both time and cost. These examples will illustrate several new ultrasonic cement-bond curves that were developed as a result of the new method and that, when used in conjunction with CBL amplitude data, improve foamed-cement evaluation. In the examples, the interpretation is focused to answer the basic question, "Should remedial cementing be performed, or should the well be perforated for production?"

Surfactant stabilized bubbles flowing in a Newtonian fluid

“…One of the benefits of foaming the cement is the increase in the viscosity. The increased viscosity with the amount of added bubbles enhances the drilling mud removal [42], especially in the type of mud used in geothermal wells [43]. Our numerical calculations show that in both particle and bubble suspensions, the viscosity increases with the increase in volume fraction of spherical suspending objects [44].…”

Foamed Cement Applications in Oil Industry Based on Field Experience: A Comprehensive Review

“…These procedures will help reduce the costs of unnecessary remedial cementing that may occur when foamed or complex cements are evaluated incorrectly. 81 Harness et al 82 developed a method to differentiate foamed cement from fluid when both have the same impedance. The method uses SVP to distinguish between solid crystalline structures such as cement and fluid.…”

“…To improve the evaluation of foamed cements, new methods have been developed, such as a statistical variation process (SVP), new bond-index curves, and special log presentations. These procedures will help reduce the costs of unnecessary remedial cementing that may occur when foamed or complex cements are evaluated incorrectly …”

“…These procedures will help reduce the costs of unnecessary remedial cementing that may occur when foamed or complex cements are evaluated incorrectly. 87 …”

Simulated various characteristic waves in acoustic full waveform relating to cement bond on the secondary interface

“…An acoustic logging is a method commonly used for evaluating cement bond quality on the first and secondary interfaces in cased borehole (Bryant, 1960;Frisch et al, 1999), especially acoustic variable density logging. At present, it is a mature practice to evaluate the cement bond of the first interface (FICB) based on the amplitude of the casing mode wave (or casing wave) from the acoustic full waveform.…”