ABSTRACT
In the Oil and Gas industries, drilling a well in both exploration and development operations is becoming more challenging due to the reservoir location and complex reservoir system. A sophisticated high-cost well structure with complex trajectory, subsea system, or even operating in deep water is sometimes unavoidable. One of the crucial factors for a successful well construction operation is to achieve excellent well integrity by having good zonal isolation throughout the target reservoir section. This requires flawless primary cementation from cement job planning, design, and up to execution. The cement bond quality will need to be evaluated by performing the post job cement execution evaluation and wireline logging cement bond log survey.
Supported with more stringent regulations, well integrity is becoming a fundamental aspect in drilling and production operations. This brings new challenges to cementing operations and subsequent cement evaluation. Flawless primary cementation is of great importance, from the job planning, design, to the execution. Post-job cement evaluations are needed by performing Pressure Match Post-Job Analysis and Wireline Logging Cement Bond Log Survey.
Key parameters in designing optimum zonal isolation cement slurry is good understanding of the wellbore technical challenges and mitigating all geological and formation-related risks, such as narrow pressure margin, gas migration risk, etc. Light cement, complicated cement composition recipes, small cement - mud weight ratio are more common these days, supported with the developing technology in cementing. These, on the other side, would impact the cement bond evaluation.
Good cement bond is crucial to ensure good zonal isolation across the reservoir intervals. Casing external coating, applied to protect casing strings from rusts, is another aspect affecting the cement bond, especially cement-to-casing bond. A more advanced cement bond evaluation tool will be required to cope with variety of cementing conditions, to enable producing undoubted log results. Thus, helping Operator in making decisions of subsequent well operations.
This paper shows and presents different cement bond log interpretation results from four wells executed with a different method of implementations, performed in a development drilling campaign in Natuna Sea, offshore Indonesia in year 2019. The paper will focus on the 9-5/8" casing cementation, on which the cement bond evaluation became one of the main attentions.
