Draft Limits Research Articles

New-Generation Drill Barge for Deep HP/HT Wells

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 99210, "Re-Engineering Barge Drilling for Deep Miocene HP/HT Frontiers in a Mature Basin," by F.J. Husband, SPE, G. Bitar, SPE, T. Begnaud, SPE, and T. Petticrew, Parker Drilling Co., prepared for the 2006 IADC/SPE Drilling Conference, Miami, Florida, 21–23 February. The full-length paper details the re-engineering of a conventional deep-drilling barge rig to deliver a new-generation high-pressure/high-temperature (HP/HT)/high-flow barge rig designed for increased reliability and specification for deep-gas-drilling programs in the U.S. Gulf Coast region. Upgrading the main power and distribution systems and high-performance pump configuration is discussed as well as auxiliary-system modifications. Introduction Although heavily explored since the 1920s, the onshore Miocene of south Louisiana has produced more economic discoveries in the past 10 years than the Flex Trend subsalt play. More-recent Miocene discoveries are deep, geopressured, and contain reservoirs that are not associated with seismic amplitude. Large discoveries have been on faulted anticlines found with the aid of detailed regional maps using well logs, biostratigraphy, and 2D-seismic data. Exploration of this play has expanded into the shallow-water shelf, which to date has produced more than 40 billion bbl of oil equivalent. Optimizing drilling performance and well control for the well design requires the right drilling rig. New-generation jackup rigs are designed for shallow-water deep gas but have draft limitations in certain areas of interest. As exploration of deep targets expands in water depths from 6 to 18 ft, the availability and performance of ultradeep barge rigs becomes increasingly valuable. The marketable Gulf of Mexico (GOM) deep-drilling-barge fleet consists of 32 rigs. Of these, few are rated to 30,000 ft. Deep gas exploration is an area of particular interest for the barge-rig market because successful exploration results could drive demand higher and diversify specification requirements of the fleet. Leveraging previous frontier rig designs and customer demand to mitigate the higher drilling risks of planned deep exploration targets, a project to upgrade Barge Rig 76 B in New Iberia, Louisiana, was undertaken to deliver a new-generation HP/HT and high-flow barge rig to execute these challenging drilling programs. Mud Pumps and System Barge Rig 76 B previously operated three 5,000-psi A1700-PT pumps. However, rig power distribution was challenged to run all three pumps simultaneously. These were replaced with 2,200-hp W-2215 pumps each driven by two high-torque 752 DC traction motors and powered by four runs of number 535 cable. The pumps are rated for 7,500-psi maximum operating pressure and weigh 115,000 lbm each. The main structure in the pump room was modified to accommodate the increased weight. The existing 5,000-psi piping and valves were replaced with 7,500-psi components. Most assemblies were prefabricated, tested, and painted at supplier facilities before installation and integration testing in the shipyard. This reduced installation time and final integration-testing time, and it streamlined troubleshooting. This was especially true for high-pressure piping that required specialized welding

Air movement preferences observed in office buildings

Office workers' preferences for air movement have been extracted from a database of indoor environmental quality surveys performed in over 200 buildings. Dissatisfaction with the amount of air motion is very common, with too little air movement cited far more commonly than too much air movement. Workers were also surveyed in a detailed two-season study of a single naturally ventilated building. About one-half the building's population wanted more air movement and only 4% wanted less. This same ratio applied when the air movement in workspaces was higher than 0.2 m/s, the de facto draft limit in the current ASHRAE and ISO thermal environment standards. Preference for "less air motion" exceeded that for "more" only at thermal sensations of -2 (cool) or colder. These results raise questions about the consequences of the ASHRAE and ISO standards' restrictions on air movement, especially for neutral and warm conditions.

Availability analysis of combustion flue gases—A case study

The thermodynamic availability of combustion flue gases was analysed and modelled. The results were correlated in a polynomial of third degree with a high degree accuracy. It was found, for combustion processes, that the availability losses may reach up to 55% due to draft and dew point limitations in most fired heaters.

Compression Tests of Welded Channel Section Columns

A test program is described investigating the compressive strength of channel section columns of slender cross section. The program consisted of different geometries of cross section, each fabricated by welding from high‐strength steel. Specimens were tested both concentrically and eccentrically between pinned ends, and for each section geometry, fixed‐ended stub column tests were also performed. Additional tests were performed to determine the local buckling load of the sections under uniform compression. The different behavior of the columns that were pinned or fixed at the ends is described, including the effect of the change in the position of the internal force after local buckling of the sections. Data on the test sections described in the paper include models of the measured residual stress distributions resulting from fabrication, the local geometric imperfection components measured in the plates after fabrication, and the measured imperfections in the shape of the overall flexural buckling mode. The test strengths are compared with predictions of the AISC Load and Resistance Factor Design Specification, the draft Limit State Australian Standard, the British Standard BS5950, Part I, and the Eurocode3 Specification for the design of steel structures. Conclusions regarding the accuracy of different specifications and standards are given in the paper.

A SAND BYPASSING SYSTEM USING A JET PUMP

All harbors and tidal inlets that are located in coastal areas have one characteristic in common-the need to bypass littoral materials that collect nearby. If natural harbors and tidal inlets are left unattended, bypassing will often occur naturally, but in the process, the harbor or inlet is usually rendered unfit for commercial or navigation purposes. Quite often, the inattention results in the total closure of the inlet. Therefore, at almost all harbor entrances and controlled tidal inlets, the natural bypassing must be augmented by secondary, usually mechanical, means. The customary technique for bypassing sand and maintaining harbors and inlets is the use of floating dredge equipment. This equipment is rugged, reliable, has been proved over and over, and appears to be irreplacable for many applications and locations. However, there are many locations and situations for which this floating equipment is not suitable and may, in fact, be detrimental or prohibitively costly. Waves of even moderate height, moderateto- high tidal excursion and currents, draft limitations, limited maneuvering area, and interference with normal navigation operations are examples of conditions which decrease the desirability and application of floating dredge equipment. Small volumes of material to be bypassed are an economic liability for the floating plant since mobilization and demobilization costs contribute extraordinarily to the unit cost for bypassing work.