2011-08-04_HYDROLOGY - P2008046 - Laserfiche WebLink

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Mr. Travis Marshall Mr. Kent Walter Ms. Wendy Cheung Page 2 of 6 suspected that a sufficient amount of excess cement was not available on -site during cementing operations at TM -4, the first of the wells drilled this year to be cemented. Cementing and cement evaluation logging were conducted by Halliburton. Cement evaluation logging was performed using a circumferential acoustic scanning tool (CAST). A CAST -Fast (CAST -F) was used to log the T1 -P and TM -1 wells, and a CAST - Monocable (CAST -M) was used to log the other wells. Both tools use a single rotating transducer operating in the ultrasonic frequencies and measure the impedance of the material directly behind the casing to assess the quality of the casing to cement bond. The logs were evaluated by specialists at Halliburton using its Advanced Cement Evaluation (ACETM) process. Each ACE report presents an evaluation of the cement to pipe bond for the entire cemented portion of the well. Based on evaluation results, the Halliburton analyst assigns a rating of good, fair, or poor to specific intervals within the well. A rating of "good" indicates that the cement to pipe bond is adequate and the overall cement seal within the designated interval is sufficient and no cross -hole communication is expected within the annulus. A rating of "fair" indicates that the cement to pipe bond is adequate but that small, isolated separations between the pipe and cement are present within the interval; however, the separations are not of sufficient connectedness and frequency to affect zonal isolation. A rating of "poor" indicates that the cement is not adequately bonded to the pipe, and therefore, zonal isolation is likely not maintained and the potential exists for cross -hole communication within the annulus. Cement records, CAST log (including gamma ray log), ACE report, and a graphical representation of evaluation results are provided separately for each of the referenced wells in Attachments A through H. Results of a cement job Distributed Temperature Sensing (DTS) survey conducted by Schlumberger at well T1 -P is also provided in Attachment A. As illustrated on the cement schematics in the attachments, the total depth logged is typically at a higher elevation than the casing point depth. The differences are due to the amount of cement remaining within the well casing upon completion of cementing and the position of the logging sensors relative to the bottom of the logging tool. Cement evaluation results for each of the referenced wells is summarized below. T1 -P (Attachment A) CAST -F log completed: May 25, 2011 Casing Depth: 2,021 feet (ft) below ground surface (bgs) Interval Logged: 40 — 2,000 ft bgs The ACE report prepared by Halliburton indicates the cement to pipe bond is adequate throughout the entire logged interval, extending from the bottom of the log (2,000 ft bgs; upper R1) to the top of the logged interval (40 ft bgs). The bond is rated as good from the bottom of the log (2,000 ft bgs; upper R1) to the lower L5 (1,324 ft bgs) and as fair from the lower L5 (1,324 ft bgs) to the top of the logged interval (40 ft bgs). In addition to the CAST -F log, a cement job DTS survey was conducted at T1 -P by Schlumberger during the cementing operation. The survey provided temperature measurements over the complete length of the cemented interval using fiber -optic technology. The real -time temperature profiles were monitored during the cementing operation. Survey results indicated that changing temperatures in the well bore over time were attributed to the cement curing process. While these results do not by themselves measure the overall integrity of the cement seal, the results do provide evidence that cement was placed throughout the intended interval.