TX 75083-3836, U.S.A., fax 01-972-952-9435.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe combination of the large number of rotary-steerable systems (RSS) currently available and the variety of well trajectories in which they are applied requires a customized range of drill bits to optimize system performance. A clear understanding of the specific tool operation, combined with in-depth modeling and physical testing, is the ideal approach for determining the demands placed on the drill bit and thus deriving its key characteristics.This paper describes a series of tests that were performed at a purpose-built drilling facility to examine the variation in directional response with different bit features. Steerability is one of the key criteria involved in RSS bit design, but stability is of equal importance, particularly in ensuring good-quality, gauge borehole for maximum steering potential. To monitor the testing, a proprietary downhole dynamics recorder was used. The recorder consists of a small, sophisticated electronic measuring device that can be either housed in a sub or positioned in a specially modified housing within an existing drillstring component. The recorder was used to gather actual downhole data at a high frequency sample rate to determine both the lateral and torsional stability of the drill bit and RSS assembly with different wellbore trajectories and parameters.Results identified that specific gauge features are crucial to the directional response of the RSS tool. In addition, the dynamics recorder allowed quantitative assessment of stability versus steerability of the critical drill bit features tested. Lessons learned from this laboratory testing have been taken to the drilling environment with excellent field results, demonstrating that matching the bit to a specific RSS tool as part of the system delivers proven drilling success.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper describes the results of laboratory drilling tests, bottom hole assembly (BHA) software modeling, and fieldtesting of the industry's first slimhole rotary steerable system (RSS) using point-the-bit technology. The first system fieldtested was 4-3/4 in. diameter for use in slimhole drilling with 6-in. bits. Test results show the RSS is controllable and predictable in behavior, and produces superior borehole quality.
The G. W. Hatch No. 1 Well in Pearsall Field, Dim mit County, Texas, was proposed to achieve horizontal penetration in the Austin Chalk formation. Pinnacle Royalty and Operating Company, Inc. (PROCO), the independent operator of the well, elected a conservative long-radius approach that allowed the use of steerable positive.;displacement motors (PDMs). The use of steerable motors resulted in a smooth well bore, relatively low torque and drag forces while drilling the horizontal reach section of the well, and the ability to steer the wellbore to total depth.Casing was set after the. first build section was completed into the top of the Austin Chalk formation in order to minimize hole problems and permit handling of any anticipated well kicks.The 1253-ft horizontal section, drilled in underbalanced conditions, positively identified producing fracture systems while minimizing the formation damage that typically results from ongoing drilling operations.Drilling continued horizontally in, an underbalanced state, although occasional flowing conditions did occur, using both rotary and slide modes of stee~able drilling.Sp~cial surface production systems were utilized to handle well flow during drilling operations. The design and field operations of this equipment were critical to the safety and success of the project. Detailed planning prevented problems during actual operations.
The geometry of a stabilizer, when it is used as a near-bit pivot within specific point-the-bit rotary-steerable bottomhole assemblies (BHAs), is critical to both stability and deflection to provide optimal directional response. This paper describes the testing of a rotary-steerable system (RSS) and unique ring gauge pivot stabilizer at a purpose-built, full-size drilling test facility. The extensive, systematic testing of a point-the-bit RSS with both full ring gauge and conventional pivot stabilizer has enabled a direct comparison of the directional response, hole quality, and drillstring vibration to be made for the various combinations tested. Aside from comparison of the ring gauge stabilizer against conventional pivot, the testing also evaluated the interaction between the gauge design of the bit and the pivot stabilizer. Test monitoring required use of a proprietary downhole dynamic data recorder (DDDR) in a specially modified housing. The DDDR was used to assess both lateral and torsional stability of the stabilizer geometries and their relationship with bit gauge style and length. Further to the laboratory testing, trial applications have been sought where severe vibration issues are problematic to efficient operation of the RSS. Use of full ring stabilization geometry with an RSS in these applications will advance the industry's understanding of downhole dynamics. Enhanced understanding, in turn, will enable more efficient drilling of better-quality directional wellbores, significantly reducing cost per foot. Introduction The introduction of RSS has given the industry the ability to successfully drill complex and challenging well profiles such as extended-reach and infill designer re-entry wells. In addition, the use of polycrystalline diamond compact (PDC) bits, combined with RSS, has drastically changed the economics of directional drilling by significantly decreasing the time taken to drill hole sections and improve the quality of wellbores drilled, thus increasing the chances of trouble-free wireline logging and running of completions. The improve-ment in economics is particularly relevant in this era of high rig rates. It is recognized that the selection of correct design of bit is crucial to the successful directional performance of an RSS. The stability and steerability of the bit are key features in matching a bit to the specific RSS, while matching the durability and aggressivity to the formation is of importance in achieving the optimal rate of penetration (ROP) and bit run life. Point-the-bit RSS can take advantage of longer passive gauge lengths to reduce hole spiraling and improve borehole quality because they rely less on side-cutting action from the gauge than do push-the-bit systems.1,2 Key focus is maintained on providing very stable bit cutting structures that resist lateral instability and provide low variance in reactive torque. Furthermore the interaction between the bit, the RSS, and the BHA elements is extremely important to the successful directional performance of the system. Maintaining wellbore quality, and in particular hole gauge, is crucial to the steering performance of point-the-bit RSS.3 One aspect of wellbore quality is the stability of the active BHA, as vibration will contribute to wellbore enlargement. BHA instability can have a significant detrimental effect on the directional performance of the RSS. Prior testing has focused only on optimization of the cutting structure and gauge geometry to maximize stability of the drill bit.4,5 This paper details the introduction and systematic testing of stabilizer geometries to further enhance stability, and thus steering efficiency, of RSS.
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