Completion Architecture: A Methodology for Integrated Well Planning

Abstract

We examine how well completion design is governed by subsurface characteristics, surface environment, and state of technology. We present a methodology of well design that takes into account geology, drilling, reservoir, and operational characteristics and constraints. The method selects pertinent configurations for well trajectory, formation completion, and wellbore components to segment, route, lift, and monitor the flow stream. We discuss how this methodology is derived from case histories in land, platform, and subsea fields. Introduction Various developments in the E&P scene have motivated this work on well completion design and its underlying methodology. First, the move to frontier fields and deepwater developments, where the subsurface and surface environments are complex and well numbers are limited, highlights the critical role each well plays in the overall performance of the field or asset. Second, in the vast number of mature fields, in which production is constrained by facilities, efficient well design is arguably the most effective means of enhancing field performance and stemming production bottlenecks from the source. Third, a wide range of drilling, completion, and production technologies have been developed in recent years in response to the increasing complexity of reservoir targets in developing and mature fields, which necessitates the development of a methodology to inform and guide the application of technology. (Prior work in this domain is partly reflected in References 1–6.) Finally, robust modeling techniques have been developed, primarily in response to technology developments, enabling a quantitative analysis of wellbore-reservoir interactions.7 General Approach We place well design on a common footing with a broad range of engineering design problems, notably those in the process industry. A process plant is typically designed with a specified feed or inflow stream and a prescribed effluent or outflow stream. Experience and basic knowledge of a range of unit operations aid in determining the plant architecture that can reliably convert the inflow stream into the required outflow within the constraints of safety, economics, operability, and process efficiency. The blueprint of the process is captured in a process flow diagram, which becomes the basis of detailed design, component specifications, integration plan, etc. We decouple the well design problem into a high-level or conceptual design phase and a detailed design phase, and allow for iterations between the two. The object of conceptual design is to determine the well architecture that can most effectively convert the inflow stream from the reservoir to the outflow stream that can be handled by surface infrastructure. With process plants, however, the inflow stream is itself determined by the well architecture, particularly the segment of the well that penetrates the reservoir. As such, we may distinguish a ‘lower’ component within the well, which is the component that penetrates the reservoir and dictates the character of the inflow stream. The ‘upper’ component of the well, therefore, can be treated as the domain that converts an inflow stream from the ‘lower’ completion into an outflow stream that meets the requirements of surface infrastructure. The requirements of the outflow stream from the well depend on what lies beyond the well, and hence depend primarily on the field environment. Dry wellheads (land and platform) have very different delivery requirements than subsea wells (with a range from proximate wellheads in varying water depths to distant tieback and satellite wells). Thus, just as the subsurface governs the ‘lower’ completion, the surface governs the ‘upper’ completion. Given that the well is a conduit between the subsurface and the surface, this dependence is self-evident. Yet, there is a third dimension that impacts well design on a par with surface and subsurface characteristics.

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