This paper discusses one-company's experience in drilling a number of wells in 4000 to 9000 ft of water depth (WD) in the Gulf of Mexico (GOM), from the technical as well as the managerial aspects of this massive undertaking. The paper lists and discusses technologies, successes, and challenges experienced under the following headings:
Differences in technology from one area to another, as well as challenges and solution ideas to minimize trouble and flat time;
Scheduling and impacts of rig contracting, along with timing and execution;
Technical support by way of historical data analysis, benchmarking, lesson feedback into well planning and construction, and knowledge management and knowledge retention (where new technical staff are easily and quickly brought up to speed);
Mud engineering and special drilling muds - both water-based mud (WBM), and synthetic based mud (SBM) are shown to be crucial to environmental compliance, cost control, and trouble mitigation depending on the area;
Hydraulics and cementing issues - modeling and validation, along with special considerations for the application of PWD (pressure while drilling), and other real-time data;
Technical challenges still to be addressed, and the way forward; and
Managerial challenges still to be addressed, and the way forward.
Drilling in deepwater, defined in this paper as water depths (WD) between 1000 and 4000 ft, and ultra-deepwater defined as WD>4,000 ft is extremely challenging from both technical and logistical viewpoints. Over the past several years, offshore well target depths (TD), and water depths (WD) have increased considerably. This trend is likely to continue as the search for hydrocarbons stretches into deeper water and/or deeper geologic horizons. Fig. 1 shows areas of current focus in the Gulf of Mexico. Experience and lessons learned are transferable to other locations as the company expands its deepwater areas of concentration worldwide. The main contribution of this state-of-the-art paper is from a lessons learned perspective, along with indications of future thinking - technical and logistical - as wells continue to be drilled deeper and deeper in ever increasing water depths in search of worthwhile hydrocarbons. From one area to another, different technologies have been applied to meet various well challenges and to find and apply drilling solutions to minimize trouble and flat time. Well designs and associated technical, scheduling, mud, and hydraulic challenges are discussed, together with problems and solutions. Knowledge-based analysis of offset well data to help reduce or eliminate past problems is discussed, with emphasis on collaborative teams drawn from appropriate technical disciplines. Refer to Fig. 2 for a schematic structure applicable to current drilling effort.
Summarized below are prevailing realizations and practices. Important technical advancements are the proper application of SBM and PDC bit technology as needed. For some of the recent wells drilled in deepwater, it is obvious that these wells are approaching or exceeding 30,000ft RKB (rig Kelly bushing) or 20,000ft BML (below mudline). Typical well schematics are shown in Figs. 3 and 4, illustrating the different mud weights, bits and casing schemes applied for different drilling conditions.