RIASSUNTO
Abstract
Although Coiled Tubing Underbalanced Drilling has proven advantageous in reducing formation damage, increasing penetration rates, and potentially eliminating well stimulation treatments it is still regarded as one of the higher risk service operations being performed in the world today. Some operators who have utilized Coiled Tubing Underbalanced Drilling previously site that unreliable downhole tools, long rig-up times, and hole cleaning issues contribute to higher costs and unacceptable risks involved with this application. In order to maximize the advantages of Coiled Tubing Underbalanced Drilling and minimize the perceived risks, careful assessment and close scrutiny of each aspect of the operation must be carried out.
This paper outlines the planning and execution responsibilities of two companies working synergistically to provide an operator with their expertise in each area of service. Contracting integrated work-over services for a Coiled Tubing Underbalanced Drilling project on a well where previous drilling operations had failed was felt necessary by the well operator to maximize the wells potential, increase the probability of success, and minimize the risk involved. Well history of the previous drilling attempts, pre-job planning and engineering, equipment and tool specifications, operational execution, and benefits achieved through an integrated approach are discussed. The results of the drilling operation and suggested improvements of the integrated service approach are also reviewed.
Introduction
Coiled Tubing Underbalanced Drilling (CTUD) of horizontal wells in Western Canada has proven to be a very effective reservoir management tool.1 Purpose built coiled tubing drilling units have emerged onto the market with a vigor to answer the call of operators who want to maximize their reservoir potential in the most efficient manner possible. Coiled tubing drilling tools that have needed to be improved upon for reliability and versatility have been re-designed over and over to meet the requirements. The actual coiled tubing itself has been manufactured at extremely high standards in multitudes of size, thickness and strength to provide service companies with a very reliable product. Other surface equipment such as production testing vessels, wellhead substructures and masts, and control units have all been manufactured to be utilized specifically for CTUD with some of the most technologically advanced ideas in the industry. As well, engineers have had ample opportunity to compare computer modeling of circulation and drag analysis results with that of actual field numbers to provide, with confidence, a more accurate picture of downhole conditions. Still, with all the upgrading of equipment, tools, and software, CTUD continues to be a very erratic service that seems to be in demand only when oil industry markets are favorable. Therefore, it would seem to be that additional problems inherent to CTUD are present which have not been fully addressed yet - risk and cost.