Common characteristics of deep water wells are narrow separation between pore pressures and fracture gradients along with, comparatively with onland, lower values for the latter. Well designing for such scenario is always been a challenge for drilling engineers. To win over this situation, often-inevitably, wells are designed with multiple casing plans leading to higher cost for already cost intensive deepwater projects. Drilling with manageable losses has been employed as a tool to reach target depths set for sections of the well. Drilling fluid additives are also effectively being used and promoted as LOT enhancers or formation-break-down-pressure improvers based on tests carried out in laboratories.

The paper presents a study of demonstration and evaluation of the performance of a mud additive (sulphonated asphaltic resins) based on extended leak-off-test values.

The paper reports results from an extensive case study carried out in a major ONGC deep water project involving several deep water wells in Krishna-Godavari Basin offshore, India.

The results presented are the demonstration of the role of mud additive in enhancing LOTs in deepwater wells as well as the validation of the technique applied for evaluations as the study incorporates sample and control well strategy for this purpose.

The drilling fluid additive was successfully employed for improving leak-off-test values/break-down-pressure in the deepwater project.

Performance of mud additive for improving LOTs by extended leak-off-test method employing digital data was evaluated and the same may be used for general application.

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