| Autor: |
Luis Jordan Andonof, Kiattisak Petpisit, Derek Lynn Buster, Tor Eiane |
| Rok vydání: |
2008 |
| Předmět: |
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| Zdroj: |
All Days. |
| DOI: |
10.2118/116146-ms |
| Popis: |
This paper presents some case histories involving multi-frequency quadrupole acoustic measurement to obtain the formation shear slowness under varying conditions. Quadrupole modes in high frequencies for fast formations acquired in parallel with low frequencies for slow formations are processed such that the final result is that the combination of both responses yield the shear slowness across the range encountered. These conditions range from large shallow boreholes with unconsolidated formations to consolidated formations where the shear velocity is faster or close to mud compressional velocity. As is well known in the industry, the monopole mode allows the measurement of shear slowness in fast formations. However, for slow formations this refracted shear does not exist which requires other means to be employed. The application of the dipole measurement which is used in wireline encounters problems in the Logging While Drilling (LWD) environment. These problems are due to the presence of the collar which greatly influences the flexural mode in the formation along with the additional signal caused by the collar flexural wave1. Cases when the shear slowness lies in the range of the fluid slowness, a special treatment needs to be considered. The fact that one frequency (high or low) is unable to accurately respond above and below this threshold emphasizes the advantage and need for having multi-frequency LWD acoustic data to accomodate the demands of the environment. Also the challenging case where the shear slowness is in the same range as the mud compressional slowness will be discussed. All these results point to the importance of the use of a multi-frequency LWD acoustic tool for shear measurements. Some quality control considerations such as the rate of penetration (ROP) need to be taken into account in order to have a successful job. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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