Ultrasonic Logging Research Articles

Ultrasonic logging across unconformities — outcrop and core logger sonic patterns of the Early Triassic Middle Buntsandstein Hardegsen unconformity, southern Germany

The recognition of unconformities in thick and monotonous sandstone successions of consistent grain size is often difficult in locally exposed surface outcrop sections and also poorly constrained by changes of petrophysical properties across the boundary surfaces. Here, a mobile ultrasonic device is tested as a time-efficient handheld logging tool to investigate relative changes in sandstone cementation and porosity across the Early Triassic Middle Buntsandstein Hardegsen unconformity in southern and central Germany. A persistent offset of 18–20% sonic transit time occurs in all tested sections across the unconformity. This offset is not restricted to single peaks but clearly separates the different sonic patterns of the Hardegsen and Solling Formations below and above the unconformity. Integrated thin section analysis, porosity–permeability measurements and gamma-density logging suggest that these changes in sonic transit time are due to major variations in sandstone cementation and the formation of secondary porosity associated with the unconformity. Field-based ultrasonic measurements thus provide a useful addition to established outcrop logging methods and may help in the non-destructive in-situ identification of porosity/cementation heterogeneities in sandstones, in the localization of unconformities and in the correlation of borehole measured sequence boundaries to outcrop analogs.

Long-term well bore integrity in Otway: Integrating ultrasonic logs, cement petrophysics, and mechanical analysis

The CO2CRC pilot project in the Otway basin of Australia has recently started injecting supercritical CO2 into a depleted gas reservoir, in what is the first geological storage project in the southern hemisphere. For CO2 geological storage to be successful, every effort should be made to ensure that CO2 doesn’t find its way back to the atmosphere for a very long time - possibly centuries. Potable aquifers and other permeable formations (e.g. hydrocarbon deposits) must also be protected against CO2 contamination. Wells are generally recognized as a weak spot in CO2 storage, where containment can break down. This is because cement, steel and elastomers can be corroded by CO2, and the ageing process will be accelerated by any defects in the cement sheath. In particular, containment must be assured across impermeable geologic barriers - the caprock. In Otway’s case, an objective of the project was to contain CO2 below a relatively short shale interval (around 150 ft in length). This represents the primary barrier, backed up by a much longer section higher up the well. This paper discusses how the integration of 3D ultrasonic imaging together with an advanced understanding of cement petrophysical properties brings about a detailed picture of the cement sheath. Caprock properties and borehole detailed shape and features can also be characterized through formation evaluation logging. The actual in-situ cement properties can then be used in a mechanical analysis of the cement-rock-casing system in order to assess the occurrence of cement defects (such as cracks and microannuli). This methodology is applied step-by-step over the short section of cement that must assure isolation across the primary barrier, providing an accurate input to long-term leak models that will estimate the risk to containment over hundreds of years.

Image analysis for debris flow properties estimation

On August 1998 some debris flows were recorded by an automated monitoring system at Acquabona creek (Eastern Italian Alps). In this paper, motion picture of the flow, timing of single coarse particles on the flow surface, geophone recordings and ultrasonic logs were used to obtain velocity, depth and particle size data for the August 17 debris flow. Analogical images, recorded from zenithal camera located along the flow channel axis, have been converted in digital format and then processed in order to obtain a suitable identification of single flowing particles. Through image analysis techniques, grain-size and surface velocity distributions of debris flows are estimated. These properties are of the outmost importance in developing a proper rheological model for debris flows. Front velocities ranged from 1.8 to 4 m/s and corresponding flow surface velocities ranged from 2.26 to 4.18 m/s. A range of slurry shear strengths and viscosities occur in different surges of the same event. These differences in rheological flow behaviour appear to be influenced by concentration of particles and by flow particle-size distributions too. Coarser slurry are related a Bingham flow and finer slurry is associated to Newtonian flow. The development of rigid plugs is an index of rheological behaviour. In the observed surge Bingham flow is characterised by plug widths between 62 and 94% of flow width for flow depth higher than 45 cm. When depth dropped below 45 cm, slurry is finer and more liquid and flow transformed to hyperconcentrated flow. Turbulent small less concentrated surges are caused by a sort of pushing effect of the following coarser debris surge.

Ultrasonic logging as a method of evaluating the static deformation characteristics of real media

The physical causes promoting a difference in the values of the moduli of elasticity determined by static and dynamic (ultrasonic and resonance) methods of investigation were examined. On the basis of analyzing these causes formulas were proposed for calculating longitudinal wave velocities in mutually perpendicular directions for loaded and unloaded states of the object of investigation. The possibility of estimating the static parameters of deformability of a real (not idealized) medium directly from the data of ultrasonic investigations, in particular, from ultrasonic logging data, was shown.

Quality Control for Pile Foundations Using Nondestructive Testing: Case Studies in Taiwan

A study was conducted in Taiwan of the quality control of drilled shafts using nondestructive testing. Ultrasonic borehole logging used for borehole quality control is introduced. Experiences from incorporation of nondestructive test methods into contract documents during the design phase, the use of a specification for acceptance of a pile during construction, and remedial measures are discussed. Three projects on quality control of drilled piles using nondestructive tests are evaluated. Interpretation based on the test results used to reach a decision for acceptance or rejection of a pile is discussed for the case studies.

Artificial intelligence as an approach to improve ultrasonic log scanning : Han, W.; Birkeland, R. Proceedings of the 20th International Symposium on Acoustical Imaging, Nanjing (China), 12–14 Sep. 1992. pp. 201–208. Edited by Y. Wei and B. Gu. Plenum Press, Vol. 20 (1993) ISBN 0-306-44585-9

Artificial intelligence as an approach to improve ultrasonic log scanning : Han, W.; Birkeland, R. Proceedings of the 20th International Symposium on Acoustical Imaging, Nanjing (China), 12–14 Sep. 1992. pp. 201–208. Edited by Y. Wei and B. Gu. Plenum Press, Vol. 20 (1993) ISBN 0-306-44585-9

Successful Cementing of Shallow Steamflood wells in California

Summary Successful cementing of shallow casing strings (150 to 400 ft) for steamflood operations in Kern County, CA, has been difficult to achieve. Lost-circulation problems accompanied by cement fallback are common. Ultrasonic cement evaluation logs commonly show the cement sheath to be severely cut with gas (air) and show numerous cases of large gaps in the cement column. Extensive remedial work typically is required for effective completions. Numerous cement formulations, including foamed cement, have been pumped to solve these problems, without apparent or consistent success. A system now has been developed that provides operationally precise low-rate nitrogen metering from commercially available nitrogen cylinders to overcome previous metering problems. Several yard tests were conducted, and 26 wells were cemented with foamed cement with a low-rate nitrogen metering system. Surface-stable foamed-cement systems have been created with nitrogen rates as low as 6.4 scf/bbl and densities as low as 6.5 lbm/gal. Results illustrate that, with proper metering equipment, typical field crews can perform foamed-cementing treatments with minimum equipment. Posttreatment evaluations demonstrate that properly designed and executed foamed-cement treatments virtually have eliminated the lostcirculation problems and gaps in the cement sheath.

Structure, porosity and stress regime of the upper oceanic crust: Sonic and ultrasonic logging of DSDP Hole 504B

The layered structure of the oceanic crust is characterized by changes in geophysical gradients rather than by abrupt layer boundaries. Correlation of geophysical logs and cores recovered from DSDP Hole 504B provides some insight into the physical properties which control these gradient changes. Borehole televiewer logging in Hole 504B provides a continuous image of wellbore reflectivity into the oceanic crust, revealing detailed structures not apparent otherwise, due to the low percentage of core recovery. Physical characteristics of the crustal layers 2A, 2B and 2C such as the detailed sonic velocity and lithostratigraphic structure are obtained through analysis of the sonic, borehole televiewer and electrical resistivity logs. A prediction of bulk hydrated mineral content, consistent with comparison to the recovered material, suggests a change in the nature of the alteration with depth. Data from the sonic, borehole televiewer, electrical resistivity and other porosity-sensitive logs are used to calculate the variation of porosity in the crustal layers 2A, 2B and 2C. Several of the well logs which are sensitive to the presence of fractures and open porosity in the formation indicate many zones of intense fracturing. Interpretation of these observations suggests that there may be a fundamental pattern of cooling-induced structure in the oceanic crust.