This is a case study of a successful, field-wide implementation of horizontal, barefoot completions in a moderately competent formation - the Alpine Reservoir in Western North Slope, Alaska, Figure 1. A barefoot completion is a borehole without tubular liners and no cemented support - the least costly but riskiest completion strategy. (In this paper, barefoot and unsupported mean the same and are used interchangeably.) The Alpine experience provides a successful example where the benefits of unsupported boreholes outweigh the risks of borehole failure. To date, this aggressive yet simple completion technique has an aggregate length of more than 160,000 ft, all unsupported. Combined with good drilling practices, the success of barefoot horizontal wells in Alpine is also due to the following petrophysical and geomechanical factors:Consistent reservoir quality within the layerAbsence of shale-breaks in the producing zoneModerate strength in normal fault geotectonic settingLow variability of strengthLinearly elastic behaviorNon-severe, slight weakening when water-saturatedGood permeability retained under post-elastic strains Introduction In general, barefoot horizontal completions are implemented only in very competent, hard formations that pose little risk for wellbore collapse and/or sand production, such as dolomites, hard limestones, hard sandstones, and shale-free siltsones. The advantages of barefoot completions are:Low completion costSimple and fast implementationPotentially lower completion skins if undamagedHigh productivity per unit length (producers)High injectivity (injection wells)Higher critical drawdown pressure for sanding However, the risks and disadvantages of unsupported, long, horizontal wells in Alpine are:Potential for collapse or sanding in weak zonesHigher wellbore stresses compared to vertical wellsCostly and limited options for zonal isolationHigher sensitivity to formation damageLimited options for stimulationLimited options for future remediationHigh friction factors for future coiled tubing workover There are very few reservoirs that are developed exclusively with barefoot horizontal wells, owing to the abovementioned risks. One recent example is described in Australia (Allard, 1998). The Alpine experience is the first reservoir in Alaska developed exclusively with barefoot horizontal wells.

Forested aquatic streams depend heavily on forest canopy input. This input is a primary resource for the macroinvertebrate fauna. As a result, changes in the canopy impact the aquatic ecosystem. The focus of this study was to identify leaf degradation rates to determine resource availability for invertebrate communities. Specifically, leaf degradation rates were determined for oak, poplar, maple and kudzu. Oak, poplar, and maple are established stream canopy vegetation while kudzu is an invasive species. By comparing leaf degradation rates of native vs. exotic leaves, it provides an insight to changes in community structure. Furthermore, these changes in the plant canopy biodiversity have long-term implications for stream health.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Colville River Field (Alpine) represents the first widespread and successful application of openhole horizontal completions on the North Slope of Alaska, and one of the first in the world. The purpose of this paper is to examine why this completion technique was selected and identify the key parameters that favored its successful application in the Colville River Field. The optimal completion technique for a candidate well is determined by the reservoir properties, geologic setting, rock mechanics, development plan and completion design. In this paper we will review the unique advantages and disadvantages of openhole horizontal completions based on the Colville River Field.From the results of the review, three key parameters were found to be critical to the success of openhole horizontal well completions and should be applied broadly in other situations. Using these three key parameters as criteria, other major North Slope reservoirs are evaluated to determine their potential for openhole horizontal completion applications. Focus areas in this evaluation include in-situ reservoir parameters, development plans, fluid contacts, and wellbore geometries. The results showed that only one other major field on the North Slope could have benefited from openhole completions.The results of this paper are meant to provide guidelines for the future application of openhole horizontal completions both on the North Slope of Alaska and beyond. .

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