Ultradeepwater wells are commonly characterized by a narrow margin between pore and fracture gradients. In these wells, even a small variation in pressure profile may lead to severe operational issues. This paper describes the drilling of high-pressure/high-temperature (HP/HT) deepwater wells through an ultranarrow pore-pressure fracture gradient (PPFG) window by means of technology application and strict procedural control.

Introduction

An exploratory well with a narrow drilling margin can be realized successfully by use of a customized design concept. Such a concept may not follow standard procedures strictly as ordinarily defined but still can fulfill the guidelines and concepts behind conventional approaches.

To apply such a customized concept, a multidisciplinary team was created to design the well through all the possible expected scenarios. An integrated assessment was prepared, evaluating how real-time monitoring could mitigate the operating risk of the exploration activity.

The operator’s guidelines used for standard parameters such as kick tolerance and choke margin were reviewed and reinterpreted for this specific application, because the introduction of new technologies could allow different design factors to control the bottomhole pressure (BHP) without affecting the margin of risk.