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Introduction Directional drilling is defined as the practice of controlling the direction and deviation of a wellbore to a predetermined underground target or location. This section describes why directional drilling is required, the sort of well paths that are used, and the tools and methods employed to drill those wells. A directional well can be divided into three main sections--the surface hole, overburden section, and reservoir penetration. Different factors are involved at each stage within the overall constraints of optimum reservoir penetration. Most directional wells are drilled from multiwell installations, platforms, or drillsites. Minimizing the cost or environmental footprint requires that wells be spaced as closely as possible. It has been found that spacing on the order of 2 m (6 ft) can be achieved. At the start of the well, the overriding constraint on the well path is the presence of other wells. Careful planning is required to assign well slots to bottomhole locations in a manner that avoids the need for complex directional steering within the cluster of wells. At its worst, the opportunity to reach certain targets from the installation can be lost if not carefully planned from the outset. Visualizing the relative positions of adjacent wells is important for correct decisions to be made about placing the well path to minimize the number of adjacent wells that must be shut in as a safety precaution against collisions. The steel in nearby wells requires that special downhole survey techniques be used to ensure accurate positioning. This section is generally planned with very low curvatures to minimize problems in excessive torque and casing wear resulting from high contact forces between drillstrings and the hole wall.
The "traveling-cylinder" diagram aids collision risk assessment during planning and collision avoidance during directional drilling at multiwell locations. Survey results can be plotted directly on the diagram, enabling an immediate visual risk plotted directly on the diagram, enabling an immediate visual risk assessment. This paper describes the conceptual basis of the diagram, how the diagram is used during planning and drilling, and how the information on the diagram can be interpreted.
For many years, directional wells have been drilled from pads and platforms close to each other with standard plan-view and platforms close to each other with standard plan-view and vertical-section drawings. Wellsite personnel sometimes have encountered serious problems with the visualization of true well separation, and convergence or divergence rates. In some instances, difficulty in interpreting the standard well plots apparently has contributed to subsurface collisions. An alternative way of displaying the information is needed to improve safety in this type of operation. To aid collision avoidance effectively, the chosen method must (1) represent a complex situation simply; (2) clearly present the relative positions and convergence rates of other wells with respect to the positions and convergence rates of other wells with respect to the plan under consideration; (3) show the actual position of the well plan under consideration; (3) show the actual position of the well being drilled relative to its planned course and to adjacent wells with a minimum of distortion; and (4) present complex 3D interwell tolerances on the allowable position of the borehole trajectory simply and unambiguously.
The traveling-cylinder diagram meets these requirements. The original hand-drawn version was developed by Lyons and Mecham for use at the THUMS offshore development wells. The procedures were gradually computerized over the years to increase procedures were gradually computerized over the years to increase efficiency and to reduce errors. The projection reportedly was derived from a technique used to check for physical interference in pipework in a chemical plant. Hough describes an early system for computerized collision checking used in the Southern North Sea in the early 1970's. The first computerized implementation of the diagram was devised in 1977. During the early 1980's, the volume of computer code used in directional drilling grew dramatically as directional contractors responded to a growing demand for engineering support. 6 Various algorithms were devised to check for interwell collisions, and software to produce travelingcylinder diagrams was developed by several companies.
Numerous references to the diagram exist in the literature, but little information on the basis of the method is available in the public domain. Because the underlying principles have not been public domain. Because the underlying principles have not been published, they have not been subjected to public discussion or peer published, they have not been subjected to public discussion or peer review. Consequently, the various implementations tend to reflect the desires of the end users and the assessments by individual designers of the computational difficulties involved. This paper shows how the four key requirements are implemented m the normal plane traveling-cylinder diagram, presents a computationally efficient implementation of the normal-plane version, and illustrates its practical application at the wellsite.
The normal-plane projection is used to display the intersection of wells with a plane constructed in space to be normal to the direction of the planned well at the point of interest (Fig. 1). The calculation is repeated at a number of points along the planned well. The results are superimposed on the same diagram (Fig. 2). The relative separation between the planned and adjacent wells is indicated by the locus of points obtained at successive depths.
Most directional wells are drilled from multiwell installations, platforms, or drillsites. Minimizing the cost or environmental footprint requires that wells be spaced as closely as possible. It has been found that spacing on the order of 2 m (6 ft) can be achieved. At the start of the well, the overriding constraint on the well path is the presence of other wells. Careful planning is required to assign well slots to bottomhole locations in a manner that avoids the need for complex directional steering within the cluster of wells. At its worst, the opportunity to reach certain targets from the installation can be lost if not carefully planned from the outset.
Sawaryn, S. J. (Consultant) | Wilson, H.. (Baker Hughes, a GE Company) | Allen, W. T. (BP) | Clark, P. J. (Chevron Energy Technology Company) | Mitchell, I.. (Halliburton) | Codling, J.. (Halliburton) | Sentance, A.. (Dynamic Graphics Incorporated) | Poedjono, B.. (Schlumberger) | Lowdon, R.. (Schlumberger) | Bang, J.. (Gyrodata Incorporated) | Nyrnes, E.. (Equinor ASA)
Summary The well-collision-avoidance management and principles presented in this paper are a culmination of the work and consensus of industry experts from both operators and service companies in the SPE Wellbore Positioning Technical Section (WPTS). This is not a new subject, but current guidance is disparate, company-specific, and occasionally contradictory. As a result, the guidance can be difficult to understand and implement. A further aim is to drive the standardization of the well-collision-avoidance rules, process, and nomenclature throughout the industry. Standardization improves efficiency and reduces implementation errors. The consequences of an unplanned intersection with an existing well can range from financial loss to a catastrophic blowout and loss of life. The process of well-collision avoidance involves rules that determine the allowable well separation, the management of the associated directional planning and surveying activities, and assurance and verification. The adoption of a specific minimum-allowable separation rule, no matter how conservative, does not ensure an acceptably low probability of collision. Many other factors contribute, such as the level of compliance by office and rig personnel with collision-avoidance procedures, and the completeness and correctness of the directional database. All these factors are connected. The material is split into eight sections, each dealing with a critical element in the collision-avoidance process. Examples are presented to highlight a good-implementation practice. This aligned approach will dispel some of the current confusion in the industry concerning well-collision avoidance; will improve efficiency when planning and executing wells; and will build industry focus on the associated collision risks when drilling. The WPTS is also supporting the current development of API RP 78 (not yet issued). This is the first of two papers. The second paper (Sawaryn et al. 2018) covers the minimum-allowable separation rule and its application, assurance, and verification.
While traditional definitions classify short-, medium- and long-radius lateral wells by angle build rates, the technology now employed to achieve those build rates suggests an industry definition which characterizes lateral wells not only in ten-ns of wellbore geometry, but in engineering terms as well.
In proposing such a definition. this paper examines new developments in downhole technology, focusing on short- and medium-radius systems to show how choice of drilling hardware can determine the type of curve drilled, as well as how it is planned and completed.
New horizontal well-planning techniques developed in light of recent hardware improvements are also discussed, while technical innovations still in development are noted.
Field results of recent lateral wells present examples of problem-solving, since a detailed discussion of lateral problem-solving, since a detailed discussion of lateral applications exceeds the scope of this paper. Concluding remarks suggest areas for further development to improve economics and performance in lateral drilling.
Renewed interest in lateral drilling centers on the economic and technical advantages of drilling horizontal holes from vertical wellbores to enhance oil and gas production. Because lateral drilling allows a large portion of wellbore to remain In a sinale zone of interest, a greater area of /one can be exposed. In addition, lateral drilling allows multiple holes from a single wellbore for completion of more than one formation or pay zone.
Therefore, lateral drilling may be defined as Implementation of a horizontal or near-horizontal wellbore designed to take optimum advantage of the three dimensional geometry of a reservoir.
A well can be further classified as a "short-," "medium-," or "long-radius" lateral depending on the designed build rate of the hole angle and hence. the radius of the curve it describes.
New developments in lateral drilling tools and well-planning techniques have refined methods of achieving the geometrical specifications of each type of lateral well, suggesting a broader definition which defines lateral drilling in engineering terms.
For brevity, a detailed discussion later in this paper is limited to short- and medium-radius technology, describing how the drilling system used determines the type of curve drilled, and thus "defines" a lateral well as short-, medium- or long-radius.
TYPES OF LATERAL WELLS
Long-Radius, For achieving extended reach off of platforms. and in applications where large horizontal displacement is needed, long-radius lateral techniques drill a directional well that builds inclination at 2 to 6deg./ 100' (30m), with a horizontal section extending up to 3000' (914m).