Calvin W. Kessler

Gravel-Pack Evaluation Using a Memory Gamma-Gamma Density Tool

Completions in poorly conselidated formations often require gravel packing or frac packing to eliminate the nflow of formation fines. The effectiveness of gravel placement in the screen-casing annulus or openhole annulus or behind casing (such as when prepacking perforation tunnels) may be qualitatively evaluated with treatment-pressure data Voics S in the gravel-packed screen-casing or openhole annu us are evaluated with data from density, neutron, gamma-tracer, or pulsed-neutron logs. When radioactive materials are used for evaluating proppant placement in the formation, however, gamma measurements are affected by the background signal produced by these materia s. This signal makes conventional density and pulsed-neutron silicon-activation techniques ineffective.

New Fullbore Production Logging Sensor Improves the Evaluation of Production in Deviated and Horizontal Wells

Abstract A new-generation production logging toolstring is being introduced with a sensor that can measure fullbore gas holdup. Unlike previous center-sampling holdup sensors (whether radioactive fluid-density or capacitance holdup), this new sensor responds to the entire cross-sectional area of the production tubulars (casing, tubing or slotted liner) occupied by gas and liquid. From this response, the holdup fractions for liquid and gas (Y1 and Yg) can be determined. The fullbore measurement eliminates previous uncertainties in holdup fractions that can occur when flowing conditions are nonuniform or when water cut is high. This new capability is shown by flow loop comparisons between measurements taken with the fullbore gas-holdup tool and those taken with previous center-sampling holdup sensors in horizontal stratified flowing conditions. The new production logging toolstring includes a high-speed, bi-directional, monocable digital telemetry system. This system permits simultaneous logging with additional tools such as pulsed neutron tools, oxygen-activation water-flow tools, or other radioactive fluid-velocity tools. The combination of production logging sensors with oxygen activation measurements are important for the evaluation in complex well completions where there are flow paths both inside and outside of the production tubulars, such as with slotted liners. An interactive wellsite production logging analysis package has been developed to utilize the improved data. Both flow-loop based and conventional slip-velocity interpretation methods are available for determining the flow rates of the individual phases. A new method for determining the downhole flow regime is presented which utilizes both the center-sample holdup and the fullbore holdup measurements.

Cement-Bond Evaluation: A Step Change in Capabilities

A new, small-diameter ultrasonic scanning logging tool has been field tested and commercially deployed for simultaneous cement-sheath and casing evaluation. The tool is designed for use in 9-5/8-in., heavy-weight casing down to 4-1/2-in. casing. Enhancements in downhole electronics, computing capabilities, and telemetry transmission allow the new circumferential acoustic scanning tool to operate on 7/32-in., 5/16-in., and 9/32-in. mono-conductor e-line cables, which allow for the data acquisition to be performed off a small foot print cased-hole unit with a smaller, lighter tool at the same logging speed as previous generation tools run off a seven-conductor e-line cable on an open-hole unit. The enhanced portability and evaluation capability in casings as small as 4-1/2 in. make the system ideally suited for land operations. Analysis of the cement data is accomplished with the same statistical variance process that has been widely used over the years to analyze data provided by all ultrasonic logging tools available in the industry, resulting in a robust and easy-to-interpret computed product in traditional, light-weight, and foam cement. The cement-evaluation process uses the measured acoustic impedance of the material in the casing-formation annulus. The casing’s internal diameter is obtained from the twoway travel time and the measured borehole-fluid travel time. The casing-wall thickness is determined from the frequency content of the reflected waveform data. Both internal diameter and wall thickness are used to determine internal and external casing wear. Legacy ultrasonic scanning tools could not provide quality data in small-diameter casing because of tool size and tool-fishing constraints and near-field transducer ring-down effects. A new, interactive job-planner program has been developed to optimize data acquisition for casing size, weight, and borehole fluids. The planner determines the number of shots per scan and maximum logging speed required for the tool to provide 100% circumferential coverage without sector gaps or interpolated data. Examples comparing the multi-conductor circumferential acoustic scanning tool and the mono-conductor circumferential acoustic scanning tool in conventional and nonconventional cement slurries are presented.