| [[file:M91Figure161.JPG|thumb|400px|{{figure number|1|}}Horizontal wells are drilled at a high angle, generally greater than 80°, with the intent of keeping the well within a specific reservoir interval or hydrocarbon zone.<ref name=Shepherd_2009>Shepherd, Mike, 2009, [http://archives.datapages.com/data/specpubs/memoir91/CHAPTER28/CHAPTER28.HTM Types of wells], ''in'' M. Shepherd, Oil field production geology, [http://store.aapg.org/detail.aspx?id=788 AAPG Memoir 91], p. 231-297.</ref>]] | | [[file:M91Figure161.JPG|thumb|400px|{{figure number|1|}}Horizontal wells are drilled at a high angle, generally greater than 80°, with the intent of keeping the well within a specific reservoir interval or hydrocarbon zone.<ref name=Shepherd_2009>Shepherd, Mike, 2009, [http://archives.datapages.com/data/specpubs/memoir91/CHAPTER28/CHAPTER28.HTM Types of wells], ''in'' M. Shepherd, Oil field production geology, [http://store.aapg.org/detail.aspx?id=788 AAPG Memoir 91], p. 231-297.</ref>]] |
− | Horizontal wells are wells where the reservoir section is drilled at a high angle, typically with a trajectory to keep the well within a specific reservoir interval or hydrocarbon zone. In a strict sense, these wells are rarely perfectly horizontal, but they tend to be near horizontal mostly, generally at an angle greater than 80° from vertical. | + | [[Horizontal well]]s are wells where the reservoir section is drilled at a high angle, typically with a trajectory to keep the well within a specific reservoir interval or hydrocarbon zone. In a strict sense, these wells are rarely perfectly horizontal, but they tend to be near horizontal mostly, generally at an angle greater than 80° from vertical. |
| Horizontal wells are drilled in a specific configuration. The tangent section of the well is drilled along a deviated well path to just above the reservoir section, to what is known as the [[Kickoff point (KOP)|kick off point]]. From the kick off point, the well is drilled at an increasingly higher angle, arcing around toward an angle close to horizontal. The point at which the well enters (or lands on) the reservoir is called the entry point. From there on, the well continues at a near-horizontal orientation with the intention of keeping it substantially within the reservoir target until the desired length of horizontal penetration is reached ([[:file:M91Figure161.JPG|Figure 1]]). | | Horizontal wells are drilled in a specific configuration. The tangent section of the well is drilled along a deviated well path to just above the reservoir section, to what is known as the [[Kickoff point (KOP)|kick off point]]. From the kick off point, the well is drilled at an increasingly higher angle, arcing around toward an angle close to horizontal. The point at which the well enters (or lands on) the reservoir is called the entry point. From there on, the well continues at a near-horizontal orientation with the intention of keeping it substantially within the reservoir target until the desired length of horizontal penetration is reached ([[:file:M91Figure161.JPG|Figure 1]]). |
− | Despite these problems, horizontal wells often end up as the best producers in a field. There are many reasons for drilling a horizontal well as opposed to a conventional well. They can produce considerable volumes of incremental reserves from what would otherwise be an underperforming area of the reservoir. Although they are more expensive to drill and are more prone to failure, horizontal wells often produce at several times the rate of an equivalent conventional well in the same reservoir. For example, experience in the heavy oil belt of Venezuela has shown that flow rates are increased significantly by producing from horizontal wells, yet they cost only 1.5 times more than vertical wells.<ref name=Hamiltonetal_2003>Hamilton, D. S., R. Barba, M. H. Holtz, J. Yeh, M. Rodriguez, M. Sanchez, P. Calderon, and J. Castillo, 2003, [http://archives.datapages.com/data/specpubs/method14/me14ch08/me14ch08.htm Horizontal-well drilling in the heavy-oil belt, eastern Venezuela Basin: A postmortem of drilling experiences], ''in'' T. R. Carr, P. Mason, and C. T. Feazel, eds., Horizontal wells: Focus on the reservoir: [http://store.aapg.org/detail.aspx?id=525 AAPG Methods in Exploration 14], p. 127-141.</ref> In the Widuri and adjacent fields, offshore Sumatra, 15% of the producers are horizontal wells, yet these provide 30% of the oil production volume.<ref name=Carteretal_1998>Carter, D. C., W. Kortlang, M. Smelcer, and J. C. Troncoso, 1998, An integrated approach to horizontal well design and planning in Widuri field, offshore southeast Sumatra, Indonesia: Proceedings of the Indonesian Petroleum Association, 26th Annual Convention, May 1998, v. 2, p. 135-162.</ref> | + | Despite these problems, horizontal wells often end up as the best producers in a field. There are many reasons for drilling a horizontal well as opposed to a conventional well. They can produce considerable volumes of incremental reserves from what would otherwise be an underperforming area of the reservoir. Although they are more expensive to drill and are more prone to failure, horizontal wells often produce at several times the rate of an equivalent conventional well in the same reservoir. For example, experience in the [[heavy oil]] belt of Venezuela has shown that flow rates are increased significantly by producing from horizontal wells, yet they cost only 1.5 times more than vertical wells.<ref name=Hamiltonetal_2003>Hamilton, D. S., R. Barba, M. H. Holtz, J. Yeh, M. Rodriguez, M. Sanchez, P. Calderon, and J. Castillo, 2003, [http://archives.datapages.com/data/specpubs/method14/me14ch08/me14ch08.htm Horizontal-well drilling in the heavy-oil belt, eastern Venezuela Basin: A postmortem of drilling experiences], ''in'' T. R. Carr, P. Mason, and C. T. Feazel, eds., Horizontal wells: Focus on the reservoir: [http://store.aapg.org/detail.aspx?id=525 AAPG Methods in Exploration 14], p. 127-141.</ref> In the Widuri and adjacent fields, offshore Sumatra, 15% of the producers are horizontal wells, yet these provide 30% of the oil production volume.<ref name=Carteretal_1998>Carter, D. C., W. Kortlang, M. Smelcer, and J. C. Troncoso, 1998, An integrated approach to horizontal well design and planning in Widuri field, offshore southeast Sumatra, Indonesia: Proceedings of the Indonesian Petroleum Association, 26th Annual Convention, May 1998, v. 2, p. 135-162.</ref> |