Fit-For-Purpose Acoustic Cement Evaluation Using Logging While Drilling in Deepwater | SLB

Fit-For-Purpose Acoustic Cement Evaluation Using Logging While Drilling in Deepwater

Published: 03/17/2015

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Schlumberger Oilfield Services

Cement evaluation is a critical part of a cementing operation. Recent industry events and the continuous tightening of regulations for cement placement have elevated the importance of cement evaluation to heights greater than ever. The initial verification of a primary cement job is performed using the pressure trend obtained while pumping, because the pressure increases as the cement rises in the annulus. The actual pressure trend can then be compared with the expected pressure to infer the actual cement height in the annulus; however, this methodology can only predict but not confirm the top of cement (TOC). In deepwater, the regulatory agencies may require physical evaluation of TOC in specific strings of the well that can require running cement bond log (CBL) tools for those strings. This would use the critical path time for every CBL run. In addition, this regulatory agency requirement can also be technically challenging because cement bond evaluation for casing as large as 18-in. that is placed in a 22-in. open hole is the upper threshold limit for conventional wireline conveyed CBL tools. Many operators are now running logging-while-drilling (LWD) sonic tools for open hole compressional data. Using the same sonic tools, logging can be performed through the casing strings on the same run and the results can be analyzed to confirm the TOC. The data presented here seems to show that the results agreed well with the predicted TOC from the pumping data. The use of this tool for cement evaluation was further validated against CBL evaluation that was performed on deeper strings in example deepwater exploration wells. The paper will elaborate on how the integration of this technology can provide precise TOC evaluation and save the operators considerable rig time per section.

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