Successful Horizontal Drilling and Gravel Packing in Deep and Ultra-Deepwater

Abstract

Abstract This paper discusses specialized completion tools and techniques developed while drilling and completing the open hole sections of 20 horizontal gravel packs and 3 Level 5 multi-lateral wells completed in Campos Basin, offshore Brazil. The discussion covers wellpath planning, pumping operations, wellpath selection, multilterals, the use of extended-longevity well screens, floating rig operations, and fluid systems to prevent formation damage. Open hole horizontal wells are attractive in ultra-deep water because the approach eliminates a liner and allows a larger casing string at the reservoir. This method also provides extensive reservoir exposure. Couple this technology with multi-laterals and a significant reduction in the number of wells to adequately drain the reservoir may be achieved. Twenty open hole completions have been successfully performed in the deepwater Marlim field offshore Brazil. These include both gravel- and non-gravel-packed completions in horizontal producers and injectors. Additionally, three Level 5 multi-lateral wells with open hole completions have been successfully installed in the same field. Multi-lateral (ML) completions have been classified as Levels 1 through 6, depending upon junction functionality. Only Levels 5 and 6 pertain to this discussion. Only Levels 5 and 6 provide pressure integrity at the junction. Level 5, a cased and cemented main bore and laterals, achieves pressure isolation at the junction with packers. Level 6 is similar to Level 5 except that pressure isolation at the junction is achieved using the casing. Introduction The economic viability of deepwater projects requires effectively draining the reservoir with a minimum number of wells. The completion types of choice are either long horizontal wells or multi-lateral completions.4 In unconsolidated formations, it becomes necessary to control sand production to effectively produce the reservoir. Open hole gravel packing has been gaining in popularity as the preferred sand control technique for horizontal wells. Significant advances have been recently achieved to substantially extend the length of laterals that can be successfully packed (with lengths exceeding 1000 meters being relatively common). Technology is also under development to reduce the negative effects associated with the presence of hydratable shales in the production interval. The fact that gravel packing helps to minimize well interventions and risk if planning and execution are properly carried out leads to this completion type being very desirable to deepwater applications. While stand-alone screens are often used for this purpose, it has become clear that gravel packing extends well life as required for economic viability of deepwater installations.5,6 Petrobras has been employing open hole gravel packing as well as stand-alone screen completions in their horizontal well and multi-lateral completions in the Campos Basin (Figure 1).1,2 To date, 20 horizontal open hole gravel packs and 3 Level 5 multi-laterals have been successfully installed from floating rigs. Both of these innovations were the first of their kind. With the success of isolated junction technology, both laterals of a Level 5 or Level 6 multi-lateral well can be effectively gravel packed. This can provide extended well life and improved reservoir management. Additionally, with the proper use of inflow control devices, relative flow from each branch of a multi-lateral can be controlled. The Campos Basin, home for 61 separate fields (seven of which are classified as giants)7 in water depths ranging from 100 to 2,000 meters, is one of the major deepwater developments in the world. In this challenging environment, Petrobras first performed horizontal gravel packs in water depths exceeding 700 meters, and the first Level 5 multi-lateral wells were constructed from a deepwater floating rig. For both of these applications, operating from a floating rig in a deepwater environment posed significant challenges that had to be overcome. In particular, successful horizontal gravel packing required that hole cleaning be effectively employed (even with the presence of a long, large-diameter riser).