Abstract

The Micro-Flux Control Method (SECURE) brings many benefits to the drilling operation, as discussed in previous publications1,3. These benefits are more dramatic in challenging environments such as deepwater, where the combination of SECURE with Surface Pressure Control (SPC) or a Surface BOP (SBOP) can eliminate more than one casing string and substantially reduce the risk of well control problems. The result is a safer, lower cost and more efficient well with less non-productive time. This paper describes the advantages of combining an SBOP or SPC and SECURE for any type of offshore well situated beyond the reach of jack-up rigs, including deepwater wells. The more challenging the environment, the more advantages the combined system brings. This paper also addresses the safety issues that are eliminated when using SECURE with an SPC or SBOP. We also discuss the enhanced flexibility that a SECURE-ready floating drilling rig equipped with SPC or SBOP brings by allowing the operator to choose the drilling method that best suits the well condition at any particular time - conventional, SECURE near-balanced, or even under-balanced. The potential economic and safety advantages for many prospects that are currently uneconomical if conventional drilling practices are used are also reviewed. Because SECURE allows the real-time determination of pore pressure and fracture gradients, the system can be used in the event that the actual formation pressures are different than predicted. This is not an uncommon situation and, without SECURE, can mean that a well is abandoned or cannot reach TD due to safety concerns or an unpredicted event such as a blow-out. With a drilling rig that can drill conventionally or in SECURE mode, the Operator can optimize the drilling process by hole section and drill any well in the most effective and economic way.

Introduction

The benefits of the Micro-Flux Control drilling method (referred to here by the acronym SECURE) are applicable to all types of wells, from onshore to offshore (including deepwater). The method is most appealing for wells located in challenging environments, including HPHT and deep and ultra-deepwater areas, exploratory wells, zones with unknown pore-pressure, wells with rapidly changing pore pressure profiles, and wells drilled in environmentally sensitive areas. The method brings cost and safety benefits in offshore wells drilled from platforms and jack-ups, without requiring many changes or additions to be made to the current equipment arrangement. However, when floating drilling rigs are used (for example, for a deepwater well), the pressure integrity limitations of a conventional marine drilling riser fitted with an SPC may limit broader application of SECURE. With the use of an SBOP on floating rigs these concerns are significantly reduced, even in deepwater, because a high pressure casing riser is used from seabed to surface. There are various ways that SECURE can be used to drill a well and two of these are described later. The important points to be considered in each mode are addressed and discussed, highlighting which operations can be accommodated and what changes may be needed in order to achieve the full benefit of SECURE.

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