Horizontal Well Technology-A Key to Improving Reserves
Authors: Thakur G.C. 
Published: March 2010

Abstract
In recent years, horizontal wells have been very successful in increasing productivity, adding reserves, and improving the overall cost effectiveness of field operations. As a result, many operators are including the utilization of horizontal wells as an important element in their reservoir management strategy.
Horizontal wells are being used in a variety of conditions: intersecting natural fractures, reducing water and gas coning, exploiting thin oil and gas zones, enhancing heavy oil recovery, tapping unswept oil, improving sweep, producing attic oil, and connecting discontinuous zones. Limited success has also been observed for thermal and low-permeability applications. In spite of documented successes in these areas, several challenges still face this technology. They include:sufficient pre-work including reservoir characterization during the candidate selection process,effectively integrating horizontal wells in over all reservoir management strategies,sufficient post-appraisal of performance versus a plan in trying to learn more about the successes and failures with horizontal wells, andthe perception that horizontal wells are only applicable in selected cases and not desirable if vertical wells are already performing well.
The presentation focusses on three items:an evaluation of horizontal drilling and completion potential of various prospects,a discussion of some advances in horizontal well technology, anda review of case studies summarizing key aspects and emphasizing the use and misuse of this technology.

Introduction
Horizontal well technology is receiving notable attention for increasing productivity, adding reserves, and improving the overall cost-effectiveness of field operations. As a result, many companies' vision involves greater utilization of horizontal wells for enhancing their profitability (see Figure 1). Provided the pre-work has been performed during the candidate selection process, horizontal wells can be used in a wide range of applications. Figures 2, 3 [Reference (1)], and 4 provide several situations where horizontal wells have been successful economically, including intersecting natural fractures, reducing water and gas coning, exploiting thin oil and gas zones, enhancing heavy oil recovery, tapping unswept oil, improving sweep, producing attic oil, and connecting discontinuous zones. Limited success has also been observed for thermal and low-permeability applications.
In spite of the above documented successes, several challenges still face this technology:sufficient pre-work including reservoir characterization during the candidate selection process,effectively integrating horizontal wells in the overall reservoir management strategies,sufficient post-appraisal of performance vs. a plan in trying to learn more about their successes and failures with horizontal wells, andthe perception that horizontal wells are only applicable in selected cases and not desirable if vertical wells are already performing well.
It is not correct to say that horizontal wells can be a saviour where vertical wells have proven unsuccessful. However, one should note that a majority of "good horizontal wells" were in reservoirs where the vertical wells were good. As a general rule, readers are encouraged to consider horizontal wells as the primary option for a field, unless otherwise applicable.