Horizontal Well Technology

Overview Of Horizontal Well Technology
Introduction
In the last few years, many horizontal wells have been drilled around the world. The major purpose of a horizontal well is to enhance reservoir contact and there by enhance well productivity. As an injection well, a long horizontal well provides a large contact area and therefore enhances well injectivity, which a highly desirable for enhanced oil recovery (EOR) applications.
In general, a horizontal well is drilled parallel to the reservoir bedding plane. Strictly speaking, a vertical well is a well which intersect the reservoir bedding plane at 90 degrees. In other words, a vertical well is a drilled perpendicular to the bedding plane. If the reservoir bedding plane is vertical, then a conventional vertical well will be drilled parallel to the bedding plane and in the theoretical sense it would be a horizontal well. Even in the reservoir with vertical bedding plane, it is possible to drill down vertically and drill side ways. The objective here is to intersect multiple pay zones. (In some instances, from the drilling standpoint, it may be easier to stay in one zone to have effective control on well trajectory.) In the mid-continental region and in the Gulf Coast region of the United States, some reservoir bedding planes are almost vertical. Similarly, in California some reservoirs are steeply deepening. Thus, while analyzing horizontal well performance, geometric configuration of the reservoir bedding planes should be considered.

A typical horizontal well project is different from a vertical project because productivity of a well depends upon the well length. Moreover the well length depends upon the drilling technique that is used to drill the well. Therefore, it is essential that reservoir and drilling engineers work together to choose the appropriate drilling technique which  will give the desire horizontal well length.
The other important consideration is well completion scheme: one can either have an open hole, insert a slotted liner, insert a line with external casing packer, or case the hole and perforate the casing, depending upon local completion needs and experience. The type of completion effect horizontal well performance, and certain types of completions are possible only with certain types of drilling techniques. Thus, well length, the well physical location in the reservoir, the tolerance in drilling location and the type of completion that can be achieved strongly depend upon the drilling method. Therefore it is very important for reservoir engineers to understand different drilling techniques, their advantages and disadvantages. Similarly, drilling engineers, completion engineers, production engineers and geologists.

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