Abstract

Considerable amounts of time and money are spent in attempting to establish behind casing seal between reservoirs and/or pseudo reservoirs (zonal and interzonal isolation). The Cement Bond Log "CBL" failed to solve the problem. A Cement Evaluation Tool CET* has been utilized to overcome Cement Bond Tool limitations and achieve distinction between good and bad cement bonding with good detection of behind casing channeles. The CET tool has been field tested in all its stages: prototype, production model, and 3 different prototype, production model, and 3 different commercial versions A, B and F. Different testing and monitoring procedures were defined by ADCO to analyse and detect the effect of perforation, acidization, communication testing and remedial cement squeezes on the primary cement compressive strength and cement distribution. In this paper a comparison has been made between CET prediction and actual communication results. Testing of the tool has been completed and results have indicated that the CET tool can provide conclusion with high degree of confidence on whether primary cementing or subsequent operations are the reasons of communication and subsequently whether cement squeezes will be successful in curing communication or not. How ever, the tool has a limitation in detecting fast formation arrivals.

Introduction

The importance of an adequate well casing cementing is essential for proper exploitation of wells. Considerable amounts of time and money are spent in attempting to establish behind casing seal especially for dual completions. Oil field cementing procedures needs both a shear and hydraulic bond between formation and casing. The former bond mechanically supports the casing in the hole. Most cement jobs provides adequate mechanical support to hold the pipe in the hole. The hydraulic bond blocks the flow of fluid across a cemented interval and reduces the danger of casing corrosion. Effective hydraulic bonding means that cement must seal the formation as well as the casing.

Evaluation of hydraulic bonding is of prime importance of petroleum engineers and drillers. The quality of cement bond can, in some cases, be interpreted from a careful study of the CBL/VDL logs; however, the conventional CBL/VDL has critical limitations of microannulus, fast formations and that it yields measures of cement bond that were circumferential average of cement quality. A new cement evaluation tool was introduced by Schlumberger to overcome limitations experienced with CBL/VDL system. It turns out that the combination of CET and CBL/VDL provides more insight into cement evaluation.

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