Establishing and maintaining hydraulic integrity between liner hangers and the base casing in which they are set has long been one of the most problematic areas facing operators. With failure rates on pressure seals in overlaps now exceeding 40% in some regions, the need for a solution to this decades-old problem has reached a critical level. Although new approaches have included turbolizers for cementing overlaps, special cements, and liner-top packers, many problems still remain. An operator and a service company are working together to develop a new drill liner hanger based on patented expandable-casing technology. This technology is being used to diametrically expand solid tubulars for a variety of drilling, completion, and remedial applications. The new liner system is designed to totally eliminate the liner lap by expanding an elastomer-coated casing into intimate contact with the casing from which the liner is being hung. Preliminary results indicate the new hanger design can result in load-carrying and burst capacities that exceed the capacity of the previous casing string. Furthermore, the overlap samples tested to date have all resulted in annular seals that have exceeded 10,000-psi differential capacities. In fact, casing has always failed during large-scale testing before any overlap leaks developed. This paper discusses the design and application of the new liner hanger and presents laboratory and field-test results. Introduction One of the long-standing challenges facing operators during well construction has been the establishment and maintenance of hydraulic integrity between liner hangers and the casings in which they are hung. In recent years, liner-top packers have been used to establish a pressure seal immediately above the liner hanger, while traditionally cement has been used to establish a pressure seal in the casing/liner overlap directly below the hanger. However, both methods of creating hydraulic integrity have frequently been unsuccessful, often because of inherent weaknesses in the design of conventional liner hangers (Fig. 1). A recent informal survey of several Gulf of Mexico operators revealed, for example, that 30 to 50% of the pressure seals in overlaps failed. Such failures not only reduce the effectiveness of the applications for which the liners are intended, but they also increase well costs because of the remedial operations that must be undertaken.

A 3,142-ft length of solid expandable openhole liner was installed successfully in a BP-operated well in November 2001. This established an industry record length and demonstrated two improvements:654 ft of liner were simultaneously expanded and pumped to the bottom of the well without the need to stop to make connections;a sliding sleeve valve permitted cement placement postexpansion prior to drill-out. These improvements delivered significant time savings and offer reduced risk plus greater flexibility in the use of solid expandable liners. This work was conducted as a technology field trial at an onshore location before trying it in the higher cost offshore environment. Key steps were taken to reduce the risks of this trial, including provisions to completely recover the expandable equipment from the well in the event of a problem. Also, risks unique to the relatively shallow depth of this installation were addressed and minimized. Introduction Expandable tubulars introduce promising solutions to some of the challenges encountered in engineering and economics of wells. A growing body of literature describes expandable tubulars mechanics, applications and field case histories.1-6 The first commercial installation of an expandable openhole liner was accomplished in November 1999. The work presented here was the 16th of 18 expandable liner installations undertaken by industry in year 2001. This paper reports fresh progress with upgrades to the knowledge and applicability of solid expandable tubulars. The concept of solid tubular expansion in wells is fundamentally proven, but as with many new technologies the commercial uptake can be slowed by end-users' concerns about risk, reliability, versatility, etc. BP's offshore operations teams have been instrumental in voicing their expectations and requirements for expandable tubulars. This in turn has enabled our drilling technology group to prioritize the goals of an onshore expandables field trials program. We believe that field trials such as the one described here are an effective way to identify areas for improvement, demonstrate progress and ultimately gain confidence that leads to faster and more efficient utilization of the new technology. Project Goals Three technical advances and a fourth technical objective were sought in this field trial: Expand more than 3,000 ft of liner. Certain deepwater drilling environments require dependable 3,000+ ft capability in order for expandable liners to be of practical use. End-users tend to view solid expandable tubulars as an unwarranted risk if success in their well entails doing something not previously accomplished. The greatest lengths run prior to this test were in the range of 2,462 ft, 2,342 ft and 2,186 ft; hence the goal was to demonstrate deployment of more than 3,000 ft length, with deepwater drilling staff present to gain first-hand experience. Expand via "scoping" technique. The term scoping describes extruding the liner off the face of the expansion cone while literally pumping the expanding liner to the bottom of the wellbore.

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British Columbia's foresters currently use height growth curves developed with data from Montana to estimate the height and productivity of western larch (Larix occidentalis). The ability of the presently used curves to accurately predict the height growth of British Columbia's larch population is unknown. The production of new curves with local data could improve our ability to predict heights and allow increasingly precise yield projections in British Columbia. Data from 105 western larch stem analysis plots were collected from across the natural range of larch in British Columbia. The measured plots were naturally established, fire-origin, even-aged, and exhibited no indications of suppression or disease. A Richards function was fit to the data from each plot and used to generate height-age and site index information. Four models were fit to the plot data: conditioned logistic, Chapman Richards, conditioned Chapman Richards, and conditioned Weibull. The Chapman Richards model had the best fit to the data, although all four models had similar fit statistics. Overall, the Chapman Richards model is slightly more accurate at estimating heights than the currently used model. West.J. Appl. For. 17(2):66–74.

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