Advanced Competion Techniques For Extended Reach Wells
Authors: Proano Enrique M. 
Published: October 2008

As the drilling phase of oilfield operations continues to evolve, completion technologies are continuously challenged to keep up and offer safe, practical and economical solutions. Among the latest trends in drilling technologies are extended-reach drilled wells (ERD). Even though there is no known official definition, a well is generally defined as extended reach if the ratio between true vertical depth (TVD) and horizontal displacement (HD) exceeds 2.5. Only a few wells with ratios exceeding 4.8 have been drilled to date. This paper discusses the completion equipment used and outlines the field operations carried out for Total Austral's extended-reach campaign in southern Argentina. It focuses on the application of new techniques and reviews the critical success factors, technical advantages and cost savings involved.

Introduction

New drilling technologies are enabling operators to extend the reach of horizontal wells to lengths previously thought impossible. Wells with horizontal displacements reaching over 10 km. are now being considered. Taking advantage of these new capabilities, the operator on behalf of a joint venture is drilling ERD wells in the remote area north of Tierra del Fuego, Argentina (fig 1). These wells tap into offshore reservoirs from shoreline locations, reducing the expense of offshore drilling and production facilities and also eliminating many environmental concerns. In addition to the drilling phase, the operator faces unique completion challenges which are being addressed using innovative techniques and state- of-the-art equipment. Conventional completion designs, when applied to ERD wells, can be highly risky, time consuming and expensive, often becoming unfeasible. One of the latest developments in completion designs is the utilization of a system that uses pressure pulse communication and microprocessors to remotely activate downhole completion tools. By applying this technique to hydraulically set completion packers, the operator and service company were able to successfully overcome the majority of time, risk and expense-related issues and additionally achieved several firsts for the industry.

Background

After having drilled three offshore ERD wells for gas lifted oil production in 1995 and 1996, it was decided to take advantage of the ERD technology to develop offshore reserves from shoreline locations. The original offshore wells had been completed in a two trip fashion. A hydraulic set packer was initially set in the well on drill pipe. Then the completion string equipped with gas-lift mandrels was stung into the packer by means of a conventional locator with seal assemblies. The current drilling campaign would include the drilling of several gas-lifted oil producers but in addition for the first time gas wells would also be drilled. These changes led to the decision to review the completion strategy. Given the remote and rather isolated geographical location of the operations (fig 1), one of the main constraints was the lack of equipment or services specially designed for such extreme well profiles. There were no coiled tubing or snubbing units available locally with the capability of reaching the intended packer setting depths, therefore, it was considered imperative not to rely on such equipment for either completion operations or contingency tasks. This decision was based both on practical and economical considerations.