The deepest well drilled to date in the Gulf of Mexico, the Well #1 discovery well in Green Canyon, required setting casing in a 15,000 ft thick section of tectonically active salt. After casing collapsed in the initial wellbore, a comprehensive model was developed to characterize wellbore stability, salt creep mechanism and implications for well design, and mitigation options for future well construction. To facilitate the construction of models characterizing the interaction of casing and salt, the regional pore pressure and insitu stress setting was analyzed. This analysis revealed that pore pressure in this area shows a significant regression in the subsalt formations. This pore pressure regression, if not accurately predicted, can lead to significant problems with the wellbore including wellbore breakouts and drilling fluid losses. The combined challenges of open-hole wellbore instability, salt creep, and casing damage made well design and construction very difficult. In this paper, models are utilized to replicate wellbore instability, salt creep and the interaction of halokinesis, wellbore geometry, casing stress, and drilling fluid hydrodynamics. The modeling reveals that casing failure was caused primarily by non-uniform contact of salt on casing thereby generating stresses that exceeded the yield strength of the lightweight casing. The same model showed that heavier casing could withstand identical, non-uniform stresses if loading was diametric and not axial. The model was used to prepare an optimized drilling program that mitigates the risk of non-uniform application of stresses by salt and non-uniform application of slip loading. Recommendations included under-reaming in the slip zone, the use of drilling fluid of appropriate composition, and cementing practices that improve the stress distribution on the casing. Further, after setting casing through the salt, relatively high mud weights were required to avoid a large differential between internal and external loading on the casing. High mud weight had implications for wellbore stability in open-hole while drilling the subsalt sections to reach the reservoir. Modeling predicted accurate in-situ stresses and pore pressures that were utilized to drill a bypass well that successfully reached an unprecedented depth of 34,189 ft. Both analytical and 3-D elasto-plastic finite element methods (FEM) were applied to analyze casing failure mechanisms, coupling the effects of in-situ stresses and mud pressures with the overburden. The methods were also applied to analyze mineralogic parameters that influence salt creep. The modeling process is applicable to essentially all Gulf of Mexico extended-reach wells to be drilled through salt sections. Introduction Subsalt and near-salt formations are among the most attractive exploration prospects in many operating areas including the Gulf of Mexico (GoM), offshore West Africa, Brazil, the Southern North Sea, Egypt, and the Middle East. One of the characteristic features of the northern GoM salt trend is that the salt bodies are highly mobile. High mobility has two significant implications for wells drilled through salt: "creeping" salt masses can exert catastrophic stresses on casing; and in areas near the salt/rock interface, salt movement can create unstable rubble zones that can make drilling difficult or impossible.

A new and reliable method for early gas influx detection is described. It is based on the increase in sonic propagation time which is observed when gas is present in the annulus. Unlike detection methods based on differential flow or pit gains, the instrumentation required for this technique is simple, reliable and cost effective. Pressure transducers which are mounted on the standpipe and on the annulus a few feet below the flowline monitor the sonic pressure waves generated by the mud pumps. The output from the pressure transducers is used to measure the rate of change of sonic propagation time around the circulating system. This quantity is strongly influenced by the presence of gas. In addition to the theory behind the technique, the paper describes controlled tests and field examples from around the world.

Improving hole quality is a major factor for accurate formation evaluation and reduced well construction costs in deepwater. Further optimization of the borehole quality using new generation drilling assemblies is now possible. Not only to improve formation evaluation, increase penetration rates, and reduce the risk of drill string failure, but also to reduce the load points of salt formations on completions. Concurrent drilling and reaming techniques have been successfully used to mitigate the effect of non-uniform, transverse loading of salt formations on completions as well as improve hole quality for higher wireline log success rates. During the execution of deepwater wells in offshore Brazil, multiple bottomhole assembly configurations were deployed to drill the various hole sections and the use of logging-while-drilling (LWD) imaging and wireline calipers provided a direct comparison of hole quality performance of each drilling system. A culmination of various drilling systems were evaluated, during a drill-off test, in a single well while performing enlarging-while-drilling (EWD) of a 12 1/4" to 14 3/4" hole. Salt formations were drilled to fully compare each system in a common drilling environment without variations due to formation types. Introduction The effects of hole rugosity and wellbore threading caused by conventional steerable assemblies is well documented in the industry, and can lead to poor cement isolation, high friction factors, near wellbore formation evaluation risk, high rotary torque, poor wireline conveyance success rates and high bha shock-loading1. Each of these conditions can have a significant impact on completion costs, reserves estimation, and drill string integrity. Integrating drilling mechanics results with an analysis of wireline and LWD data, the authors demonstrate a significant improvement in hole quality while drilling with a new generation rotary steerable system in combination with concentric reaming devices, compared to conventional directional drilling and hole opening combinations. For this paper, hole quality refers to the final caliper hole size and shape from threading and not formation damage aspects of the final wellbore. Wellbore threading is the existence of uneven grooves inside the wellbore much like the threads on a bolt. Theory As the well designs and casing programs become more complicated in many deepwater applications, operators have looked for methods to reduce the maximum casing size required at the surface while still maintaining the production tubing size to meet project economics.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAnadarko Petroleum Corporation spudded a shallow kick-off extended reach well from the High

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