Economically marginal wells, sometimes critical in their own right, can require tight equivalent-circulating-density (ECD) control just like their expensive HTHP, deepwater, and extended-reach counterparts. Limited budgets or well conditions, however, may preclude use of pressure-whiledrilling (PWD) technology. This paper presents a case history where the ability to manage ECDs from within a remote, realtime operations center was tested on an HTHP well in the Gulf of Mexico and subsequently on a low-budget land well in the western United States. Field results demonstrate that it is possible to obtain high-quality ECD information without running PWD tools.
Special hydraulics software run at the operations center provided virtual sensors for equivalent circulating and static densities while drilling, tripping, and running casing. PWD data was available for comparison on both wells, except for the lower intervals of the HTHP well. In the latter well, high formation temperatures exceeded tool limits, so it was necessary to rely strictly on computer simulations for ECD management.
The primary purpose of this paper is to critically review these case histories to help assess the spectrum of opportunities for ECD management from remote operations centers. Field results, operational issues, planning requirements, training efforts, and technical and business drivers are among the topics that will be presented and discussed. Lessons learned and recommendations for future efforts are also included.
ECD management is among the most pressing concerns for drilling wells safely, economically, and efficiently. Narrow operating windows in today's most critical wells are continually tested by elevated ECDs during drilling, tripping, and casing operations. Drilling fluid density is required for pressure control and wellbore stability; viscosity and flow rate are needed for hole cleaning and barite-sag mitigation; gel strengths are required for static suspension of cuttings, etc. Finding the proper balance among these parameters is the goal of ECD management.
The advent of pressure-while-drilling (PWD) technology and the resurgence of real-time operations centers (OCs) independently and collectively have increased ECD-management opportunities. PWD and other real-time data transmitted from the rig allow drilling teams, OC personnel, and others to interact with rig personnel to achieve quality ECD programs. However, this combined service basically has been limited to high-budget, critical wells. The term "critical" previously has been applied to drilling projects that "possess several of the following attributes: high risk, frontier location, remote, deepwater, great depth, expensive, technically difficult, adverse environment, environmentally sensitive".1 Clearly, "narrow operating windows" should be added to this list.
Other wells also have this need, but a high percentage of these probably cannot take full advantage of this PWD/OC combination for ECD management. Many do not have the budget to run PWD tools, or the drilling visibility to rate OC attention. In other cases, high temperatures preclude use of PWD in intervals where the data would be most valuable. Furthermore, PWD technology is not available on any well during certain critical operations such as running casing.
PWD "technology gaps" have been successfully addressed by a real-time hydraulics system2,3 (RTHS) that complements PWD when measurements are available and substitutes for PWD when real-time measurements are not. The RTHS has primarily been a wellsite service; however, new opportunities are created when it is used in conjunction with a real-time OC. This refinement was tested when the simulation computer was installed in Shell's New Orleans real-time operations center (NOOC) instead of at the rigsite.
The first two case histories involving real-time hydraulics simulations from within an OC are discussed in this paper. The first test was conducted on a critical Gulf of Mexico shelf well. It was expected that HTHP conditions would eventually prohibit use of PWD tools. The second case was a high-visibility, but low-budget land well in the Pinedale field in the western United States.