Multiwell Field Examples for Lightweight Cement Evaluation Using Tight Processing from Pulse-Echo and Pitch-Catch Data
Authors: Govil Amit , Palacio Guillermo Obando , Middleton Roy G. , Mueller Dan T. 
Published: February 2025

In this paper we address the challenge of identifying lightweight or foam cements during cement evaluation. Our primary objective is to present an innovative approach that uses well logging ultrasonic data and processing for accurate assessment. Specifically, the focus is on overcoming issues associated with identifying these unique cement types. The method named tight solid-liquid-gas (SLG) processing, is introduced as a novel technique to enhance the evaluation of lightweight cements. Leveraging both pitch-catch dataset and pulse-echo measurements, this approach involves intricate processing to extract valuable insights. By employing these resources, the technique aims to provide a comprehensive understanding of the cement's integrity, surpassing the limitations of traditional evaluation methods. Tight SLG processing enhances discrimination of lightweight solids from displaced muds and identifies microannulus or microdebonded cement. It uses a four-envelope cross-plot, instead of the standard three-envelope SLG crossplot of acoustic impedance from pulse-echo vs. acoustic impedance from flexural attenuation.

The application of tight SLG processing on ultrasonic data marks a novel development in cement evaluation, evident in the detailed reprocessing of log data from multiple legacy wells. This in-depth analysis has revealed significantly more solids within the annular space than were previously observed, significantly advancing our understanding of the cement bond. Notably, the identification and allocation of these ‘new’ solids within the fourth envelope helps identify previously uncharacterized microdebonded cement. This discovery is a crucial breakthrough, surpassing the capabilities of traditional evaluation methods. A key innovation in our approach involves a pre analysis of pitch-catch data, a critical factor in distinguishing materials within the annulus. This enhancement has proven instrumental in identifying materials besides fluids or formation. The refined sensitivity provided by pitch-catch data has unveiled previously undetectable details. These findings affirm the efficacy of tight SLG processing in overcoming the challenges associated with lightweight and foam cements. The identification of microdebonded cement and the differentiation of materials within the annular space emphasize the transformative potential of the technique. In conclusion, the results obtained through tight SLG processing in lightweight or foam cements represent a pivotal leap in cement evaluation methodologies, offering enhanced accuracy and contributing to the broader understanding of well integrity in the oil and gas industry.

In this paper we introduce a groundbreaking advancement in well logging by highlighting the effective use of tight SLG processing for cement evaluation in lightweight or foam cements. The integration of pitch-catch data and pulse-echo measurements in this approach represents a novel contribution to the field. By overcoming the challenges specific to lightweight or foam cements, our technique offers a valuable tool for the oil and gas industry, ensuring the integrity of wells construction and marking a significant leap forward in well logging methodologies.