Mr. Erik Milito - The House Committee on Natural Resources ...

ISOLATING POTENTIAL FLOW ZONES DURING WELL CONSTRUCTION 39
7 Post-cement Job Analysis and Evaluation
7.1 Material Inventory
One important aspect of the post job analysis is material inventory after cementing operations are complete. A final
inventory of material should be completed and compared to the pre-job inventory as described in the cementing
execution section. A material mass balance, comparing the job plan to the actual final inventory, will determine if the
correct amount of cement and additives were used during job execution.
7.2 Job Data
To further evaluate the cementing operations, the real time data can confirm fluid volumes, densities and rates in
accordance with the initial design. Using computer software, the acquired versus predicted data can be compared to
obtain pressure matching, equivalent circulating densities and confirm well security. When problems occur during the
cementing operations, this information can be useful when investigating job failures.
Comparison of the predicted and actual job data may provide verification of placement, or insight into other issues.
Prior to the cementing operation, a checklist can be prepared from the job design to ensure all requirements have
been achieved after execution is complete. <strong>The</strong> checklist should include all critical job information such as rates,
volumes, densities, pressures, fluid rheologies etc.
Job data collected for a complete analysis can serve as a reference for future wells drilled in the same or similar
areas. <strong>The</strong> knowledge may also be shared with other operators to better understand the reasons why wells flow after
cement.
7.3 Cement Evaluation
Formation integrity and cement placement and strength are important parameters to be evaluated before drilling the
next hole section. Failure to achieve a positive test may be due to inadequate seal by the cement in the annulus or
failure of weak formations near the shoe. When the LOT or the FIT results are inadequate, the operator can perform
a cement squeeze or other treatment to enhance the formation’s pressure containment integrity or to seal a leaking
cement sheath in the annulus. A repeat LOT or FIT may then confirm the squeeze or treatment results in increasing
the interval’s wellbore pressure containment.
In order to effectively evaluate a cement job, one should determine whether the objectives of the operation have been
achieved. <strong>The</strong> objectives will vary depending on the cement job. Field evidence of a properly executed job may
include records of spacer density and rheology, slurry density control, pump rates, pump pressures and observed
returns which conform to the cementing plan. Based on the job objectives, multiple techniques are available which
include temperature, noise, acoustic and ultrasonic cement logs.
Caution should be exercised when using cement evaluation logs as the primary means of establishing the hydraulic
competency of a cement barrier. <strong>The</strong> interpretations of cement evaluation logs are opinions based on inferences from
downhole measurements. As such, the interpretation of cement evaluation logs can be highly subjective. Refer to API
TR 10TR1 for an overview of the attenuation physics, features and limitations of the various types of cement
evaluation logs.