Case Histories - Implementation Of New Liner Hanger Technology In South Central Venezuela Significantly Improves Operations In Complex Wells

Abstract

Abstract Liners hangers are used in deep drilling operations to eliminate the need to run full strings of casing. Unlike regular casings that are installed back to surface; liners will be terminated downhole at a hang-off point in the last casing. Deploying liner hangers can be very difficult, depending on the wellbore conditions. In many scenarios, the bottomhole assembly (BHA) must be rotated and/or reciprocated in order to set the BHA at the target depth, and conventional liner hanger systems often do not permit tool rotation due to the complex design. Liner-hanger failures ultimately can be the cause for losing the wellbore or a section of the wellbore, which in turn, will result in additional well construction costs to sidetrack and drill another section through the production zone. This paper will discuss the use of an expandable liner hanger that has a less complicated design that withstands aggressive reaming as well as drilling to depth. This expandable system has no external moving parts such as slips, hydraulic-setting cylinders or separate liner-top packers, which are used in conventional liners. These attributes help mitigate the risks associated with the deployment exercise and the complexity of the completion. PDVSA embraced this technology to help them optimize operations in their deep wells in which extreme environments, often close to 300°F, with deviations greater than 60 degrees and setting depths of more that 12,000 feet are encountered. The benefits that have been gain by adopting this technology are:Optimized capital expenditureOptimized rig-time efficiency (reduced NPT)Avoidance of costly redundant conditioning trips, hanger damage, and premature settingElimination of external moving parts on hanger assembly (reduced complexity)Reduced rig timeImproved reliability and fluid flowNo slip damage to supporting casing Case histories that compare the traditional and expandable liner hanger systems and verify the advantages stated above are presented. Introduction The two case history wells discussed in this paper are located in the state of Barinas and Apure in Southern Venezuela (Figure 1). Using expandable liner hangers in Barinas and Apure have provided two very important functions in the well construction process. The first function was to support the weight of the liner, and the second was to provide a positive seal on setting that would isolate pressure differentials between the wellbore section above the liner hanger and the wellbore section below the liner hanger. A common problem in the industry concerns the fact that failure of conventional hangers normally occurs during the deployment of the liner or during the setting process, which can be due to a variety of reasons:Cement integrity at the liner top (Agnew, et al, 1084)Premature setting of the liner hangerInability to reach target depthProblems with conventional tools (darts, plugs, setting tools, etc.).