Application of Downhole Video Technology to Multilateral Well Completions

Abstract

Current downhole video systems have successfully been used during the multilateral completion process. The technology is specifically being applied to the testing, inspection, and evaluation of multilateral junctions. Some examples are presented, complete with video footage from different stages in the process of building a multilateral junction. Downhole video field data is also presented demonstrating cases of properly milled casing windows, malfunctioning whipstock equipment, and a casing window inadvertently drilled in an unconsolidated formation. Introduction Confidence in the mechanical integrity of a multilateral junction can be greatly increased with downhole visual examination. Downhole video technology can be used to increase the economic attractiveness of multilateral completion methods by decreasing the risks involved with unknown multilateral junction integrity. It can also provide unique diagnostic information during the drilling and completion to more efficiently complete wells utilizing multilateral technology. Multilateral Technology Background Multilateral completion technology is being used more in recent times due to the positive experiences gained in improving the economics of producing oil and gas in some areas and situations. This technology makes economic sense by reducing the number of platform slots required offshore, reducing cuttings and mud disposal costs, reducing drilling time, increasing zone exposure, and increasing recoverable reserves. Multilateral completions have been classified into four types, or levels, of increasing technical difficulty and expense. - Level 1 is the simple open hole completion type.–Level 2 is a cased bore re-entry with an open-hole lateral or a liner hung in the lateral.–Level 3 is a cased trunk and lateral joined mechanically, but having no pressure seal.–Level 4 multilateral completions have both mechanical and pressure integrity at the junction. As the technical difficulty and investment in rig time and equipment increases, it becomes increasingly important to verify the results and to be able to quickly solve any problems that may arise during the installation. This is especially true of the Level 4 type multilateral junction. Considerable effort is made to establish the pressure seal in these completions, and verification of that seal is important. Downhole Video Technology Background The first camera patents related to borehole imaging date from the 1950s. By the 1970s downhole video cameras were commercially used in shallow water wells. This downhole imaging proved to be very helpful and the technology became commonplace in the water well industry in the late 1970s and continues to this day. By the 1980s, downhole video technology had advanced to the point where it began to be utilized in some shallow, low pressure segments of the oil and gas industry. Some imaging systems did not provide video, but only provided a still image, updated after a period of several seconds. These had limited use regarding inflow characterization, due to the lack of image movement. Today, state of the art downhole video systems provide high resolution, full motion, real-time, interactive visual examination of downhole equipment, conditions, and fluid flows at the depths and pressures needed for them to be useful during multilateral completion operations. P. 517^