Consideration of the full cycle asset development plan from appraisal through abandonment reduces the risk of missed future opportunities caused by well systems design constraints. For example, reservoir pressure depletion and subsidence can impact borehole stability to the extent that complex well designs are necessary to fully exploit the asset. Well placement not only depends on the subsiding reservoir section, but also on the reaction of the overlying geological section that must be drilled through to reach the reservoir. For land-based operations, the consequences of well complexity may be more easily addressed, the downside being a poor estimate of field recovery that can either rob opportunities for outlying prospects or, in the worst case, cause the asset to be uneconomic. For major capital projects (MCPs) such as deepwater subsalt fields, the capital outlays are immense, with single wells costing up to $100,000,000. For these deepwater MCPs, fewer wells are required to produce reliably for longer periods.
The capability to characterize rock mechanical properties from the standard P-wave acoustic datasets, either seismic or openhole log derived, enables well planners to link the Explorationist and Well Engineer's visions using mechanical earth modeling technology. The accurate assessment of formation rheology, or stiffness, and architecture (distribution and structure), allows the asset team to optimize well systems design, considering placement and production management practices over time.
The presentation will introduce acoustics-based rock mechanics concepts, describe the acoustics-based rock property prediction technique, and present field applications that demonstrate the impact of the subsurface model to the corresponding well systems design.
The involvement of the Well Engineer (WE) competency from the earliest phases of exploration is reaping economic benefit for MCPs at Chevron. This early involvement insures the maturing well system design maintains the flexibility to accommodate design-base change that often occurs as the subsurface picture evolves over project time. This early WE involvement enables:
Proper alignment and the rigorous application of well engineering risk assessment processes for MCPs.
Balanced functional objectives in conceptual field development plans.
Proper alignment of management expectations, setting of project objectives, and benchmarking for well engineering activities.
Appropriate management of well design changes and execution team handoffs.
The schematic in Figure 1 shows the increased value derived from Good Project Definition in the early project-planning phase (red and yellow shading). When good project definition is achieved in the early phases, there can still be relatively high value creation even if the project is poorly executed (see blue shaded area). This important learning, (i.e., poorly executed) projects can generate significantly more value than superbly executed projects that have been poorly framed, has been identified by a widely used third party industry benchmarking consultancy, as a MCP execution improvement opportunity.