Monodiameter Drilling Liner - From Concept to Reality

Abstract

Abstract Many in the oil and gas industry initially viewed the idea of a monodiameter well as a radical concept. But with the recent success of a field trial well, the monodiameter well has moved from concept to reality and is now a viable well construction process. The monodiameter well is a breakthrough in the oil and gas industry. This technology allows multiple strings of the same size drilling liner to be installed in a well without a decrease in internal diameter (ID). The elimination of reducing ID is accomplished by an over-expansion of the monodiameter drilling liner and the base casing in the overlap section. The monodiameter well construction process involves installing a monodiameter drilling liner below the casing and expanding it and the overlap. The resulting ID will allow additional monodiameter drilling liners to be installed and expanded without reducing the ID experienced in a standard telescoping casing program. Thus the expansion of the monodiameter liner creates a single ID. The benefit of the monodiameter well construction process is that it reduces total drilling costs, especially in challenging areas, and enables operators to maintain the well's optimum completion diameter. This paper briefly discusses the monodiameter drilling liner's transition from concept to reality, and focuses on the field installation of the monodiameter drilling liner. This paper also discusses the potential cost savings of using the monodiameter well construction process. Expanding Acceptance Initial industry reluctance to accept solid expandable tubular technology as a viable well construction method has been overcome with successful and reliable installations as well as equipment evolution. In less than four years, solid expandable technology has progressed from a concept test of expanding tubulars on the surface to deploying them successfully downhole on land and offshore. This technology has been proven in multiple installations in the same well, in high-angle and horizontal wells, and in deep and hot wells1. The logical progression of solid expandable tubular systems took the technology from being thought of primarily as a solution for drilling problems to incorporating the technology into the initial well design and drilling plan. Technical Evolution The demand for energy in the current environment continues to drive the oil and gas industry to develop systems to reach reservoirs previously unattainable due to economics, technology, or safety. One of those systems involved rethinking how casing was run in the hole by developing a way to reduce the tapering effect downhole. The conventional well construction process uses standardized casing sizes at each casing setting depth. This process takes into account that a sufficient casing size at total depth (TD) is required for a completion that will allow hydrocarbon deliverability at economic payback rate. The top casing size is determined by designing for each of the casing sizes plus clearance until the production casing has been reached. Casing size tapering results in drillpipe, bottomhole assemblies (BHA), and associated handling equipment being reduced in size as well. Using solid expandable tubulars reduces changing out of the drillstring, BHA, and handling equipment. The arrival of solid expandable tubulars to the energy industry began a well construction evolution in which the conventional diametric tapering can be significantly reduced (Figure 1). Instead of the evolution occurring in defined sequential steps, a full range of solid expandable tubulars between 16 and 5–1/2 in. exist in single and nested expansions. API casing sizes allow a quantum step from reduction to elimination of diametric tapering in the middle to upper sections of the well plan2. The open hole liner is the initial phase in diametric efficiency (DE) in which a single drilling liner is expanded to the ID of the base casing. This expansion, while it does not expand the base casing, results in reclamation of diameter. To illustrate diametric efficiency, consider 9–5/8 in. base casing in which a 7–5/8 in. casing string is to be installed. A standard 7–5/8 in. casing string results in a 19% reduction in diameter while an expandable 7–5/8 in. reduces the ID only 10%. The expandable 7–5/8 in. solid expandable tubular reclaims 0.80 in. of diameter for a 48% increase in ID.