{'fraction_non_alphanumeric': 0.013748191027496382, 'fraction_numerical': 0.001447178002894356, 'mean_word_length': 5.460280373831775, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Accurate Determination of Annular Content Behind Casing and Prevention of Remedial Action During Well Construction


 As oil and gas fields mature, many wells are scheduled for permanent well abandonment or permanent abandonment of a section for subsequent slot recovery. We present a novel data interpretation workflow that integrates pulse-echo inversion to accurately predict borehole fluid properties and sonic attenuation with ultrasonic measurement to accurately define the annular material present behind the casing.
 Per the NORSOK D-010 standard, the requirement to qualify a well section for further drilling is to evaluate any degradation of the main bore casing, along with evaluation of the well barrier element. In an example slot recovery well, pulse-echo measurement and a cement bond log were recorded in the main borehole. The data was interpreted using an industry-available cement evaluation workflow to indicate the presence of very low impedance material (gas column) between two casings up to surface. The presence of a gas column required remedial action to mitigate well integrity issues during well construction. Advanced cement interpretation was conducted using a newly developed workflow that integrates new pulse-echo inversion and sonic attenuation measurement. The novel pulse-echo inversion accurately determines azimuthal as well as depth variations in the acoustic impedance of the borehole mud. The inversion is validated using 3D models without prior knowledge of mud properties. With the help of in situ measurement of mud properties, we can now visualize features such as mud deposition and segregation in deviated pipes as well. This new processing enables easier and more accurate interpretation of the cement sheath together with providing essential information about the logging fluid. The obtained results clearly identified the presence of solids and liquids in the annular space, which helped the operator to make informed decisions for continued slot recovery and new well drilling operations, rather than spending rig time on gas column mitigation measures. Advanced cement evaluation measurement and interpretation techniques reduce risks and enable accurate and critical decision making for well construction, intervention, and plugging and abandonment in many conditions that were previously ambiguous.
 Novel three-parameter inversion for pulse-echo measurements delivers unmatched accuracy for identifying the annulus material, as well as critical information on the logging mud, leading to a high level of confidence on cement placement. This aspect is especially critical in ensuring correct evaluation in complex new well designs including vertical, deviated, or horizontal pipes with a variety of mud types.