Techniques and Deflection Tools in High-Angle Drilling: Past, Present and Future
Authors: Pickett George W. 
Published: December 2007

Directional drilling is used extensively in the oil industry, and also has many uses in other fields. Early directional drilling is discussed in detail to familiarize the reader with its terminology and to help him more fully understand the need for improvements. In the past 10 years, directional drilling companies have developed many new, tools and techniques. Advantages and disadvantages of these improvements are pointed out in this article.

Introduction

Directional drilling, which was started in the early 1930's, has found a respected place in the oilfields of the world. In recent years it has become a highly scientific and technical profession. In the mid 1950's, engineers took directional drilling in hand and the established methods that were based entirely on experience began to give way to modern techniques. These techniques were designed to improve the mechanics of directional drilling and to reduce high costs of directional drilling jobs. This article presents the many improvements that have been made in directional drilling equipment and techniques in the past 10 years. The article represents the views of the author as obtained from experience as a directional driller, and from interviews with directional drilling representatives both in management and on the field engineer level.

Uses of Directional Drilling

The proper approach for illustrating these many improvements must begin with an understanding of directional drilling and its many uses. As applied to the oil industry, the deflecting of wellbores comes under three general headings.

Sidetracking, in its most popular form, involves going around a fish left in the wellbore. Another example: when a producing reservoir is missed, a plugback and the accompanying oriented sidetrack can give a much more favorable bottom-hole location structurally. Sidetracking has been used often in secondary recovery work in both cased and uncased holes to move the bottom-hole location to an area of less depletion. A second general heading involves straightening or straightening up of a wellbore. This operation is mainly concerned with moving the bottom-hole location back to the proximity of the surface location. Typical applications would be drilling contract commitments, lease line obligations and bottom-hole well spacing requirements. A third general heading, and by far the most important, is planned directional drilling which has numerous applications, the largest being in offshore drilling operations. Platform-type directional drilling programs involving multiple wellbores have many cost-saving features, in both drilling and production phases. In multiple-well platforms of four to six wells, the initial costs would be equivalent to those of five or six individual vertical wells. However. with platforms of 12, 18 and 24 wells, economic operation is realized. Expensive rig moves are eliminated. The close proximity of multiple wellheads greatly simplifies gathering systems and production techniques. Under this same general heading fall relief wells that are drilled to kill uncontrolled blowouts. This application has no parallel in many instances. Another application involves inaccessible well sites. Typical examples are wells drilled under lakes and rivers, under populated metropolitan areas and difficult terrain such as mountainsides. Another use of directional drilling principles is the drilling of drain holes where many "roots" extend from a single wellbore in thick producing zones. These drain holes produce some of the most rapid drift angle buildups that are known, often 2 degrees/ft or angles completely horizontal. Other applications of directional drilling that are of interest would be drilling wellbores into shallow sulfur deposits and using super-heated steam to melt the sulfur for production. Completely opposite production techniques are planned for a potash field in Canada. Twenty to 25 wells are being directionally drilled to circulate a freezing medium and solidify underground water formations for a mining operation. Directional drilling has been used in recent years to tap underground nuclear explosion sites to obtain samples for radioactive analysis. Directional wellbores have been guided from mountain sites to intersect with tunneling operations for air purification purposes.

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