Cement-Integrity-Evaluation Solution in Extended-Reach Wells in the South China Sea

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The combination of ultrasonic pulse-echo and flexural-attenuation measurements was adopted in this project in the South China Sea for cement-integrity evaluation. This new method aids in understanding why integrity losses occur in certain sections, by analyzing third-interface information uniquely provided by flexural-wave imaging, and in formulating improvement actions for future cementing jobs. This method achieves a more-explicit cement-integrity-evaluation result with detailed graphical annulus information compared with the limited output from conventional acoustic measurements.

Introduction

In the Weizhou field in the South China Sea, most of the development wells are drilled as long extended-reach wells with a deviation greater than 70°. The wells are designed to reach more than 70° deviation at a very shallow depth (approximately 900 m) compared with the total depth of the well (approximately 4500 m). In a typical well, surface casing (13.375 in.) runs beyond the kick-off point and reaches maximum deviation of the well at a shallow depth (approximately 900 m). Intermediate casing (9.625 in.) runs from surface to more than 4000 m, with three different fluids/slurries pumped in the annulus: regular-weight tail cement (1.90 g/cm3), freshwater displacement cement, and lightweight lead cement (1.58 g/cm3). The completion liner (7 in.) hangs on the intermediate casing, with 1.90-g/cm3 cement pumped in the annulus.

A campaign was planned to perform cement-integrity evaluation in five wells (A9, A10, A1, A2, and A3). The basic information about these five wells is listed in Table 1 of the complete paper. The objective for Well A9 was to evaluate the 7-in. completion casing, and the objective for the remaining four wells was to evaluate the 9.625-in. intermediate casing.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 25027, “Solution to Cement-Integrity Evaluation in Long Extended-Reach Wells: New Record in the South China Sea,” by Jun CaiYongde Gao, andMingjie Zhang, CNOOC, and Lei Cui and Hongzhi Guo, SPE, Schlumberger, prepared for the 2014 Offshore Technology Conference Asia, Kuala Lumpur, 25–28 March. The paper has not been peer reviewed. Copyright 2014 Offshore Technology Conference. Reproduced by permission.
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Cement-Integrity-Evaluation Solution in Extended-Reach Wells in the South China Sea

01 May 2015

Volume: 67 | Issue: 5

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