Bottom hole assembly

Wells may be drilled at a constant angle to the target or dropped off to a lower angle through the reservoir section. To build, maintain or drop the deviation angle stabilisers are run in the bottom hole assembly (Fig. 3.15). A change in deviation used to require a round trip to change the position of those stabilisers in the bottom hole assembly. In recent years, adjustable, hydraulically activated stabilisers have been developed. The... 

Bottom hole assemblies and certain types of downhole equipment (e.g. logging tools, MWD tools) cost several US 100,000. Some logging tools will have radioactive sources which may need to be recovered or isolated for safety and legal reasons. However, prior to commencing fishing operations, a cost - benefit assessment will have to be made to establish that the time and equipment attributable to the fishing job is justified by the value of the fish or the cost of sidetracking the hole. 

BHA — Change bottom hole assembly DMF — Down hole motor failure DSF — Drill string failure DST — Drill stem test DTF — Down hole tool failure LOG — Run logs CM — Condition mud CP — Core point DP — Drill plug FM — Formation change... 

Bottomhole Assemblies. In general, the drill pipe, drill collars and, in particular, bottomhole assemblies for air (or gas) drilling operations are the same as those in mud drilling. However, because the penetration rate is much greater in air (or gas) drilling operations due to the lack of confining pressure on the bit cutting surface, care must be taken to control unwanted deviation of the borehole. Thus, for air (or gas) drilled boreholes, a packed-hole or stiff bottom-hole assembly is recommended. 

Bottom-hole assembly (BHA) Assembly composed of the rock bit, stabilizers, reamers, drill collars, subs, etc., used at the bottom of the drillstring. 

Stronach, G. R., Voden, G. S., Hubbard J- S., Ming, C. M. Northcutt, J. C. 2001. Engineered bottom hole assembly design and equipment selection criteria proved to be key factors in a challenging drilling environment, SPE paper number... 

Bottom Hole Assembly (BHA) The combination of bit, downhole motor, snbs, survey probe, and non magnetic collars assembled at the leading edge of a drill string. 

A. Wilson, G. E., How to select bottom-hole drilling assemblies, Part I, Publ. No. 62, Drilco, Division of Smith International, Inc., Houston, 19XX. 

Assemble an arrangement as shown in Fig. 105, using for this purpose two clay flower pots or chamotte crucibles of a different size with a hole in their bottom. Fill the space between the pot walls with dry sand. Insert a carbon electrode through the bottom holes of the pots and fasten it in a clamp. Triturate several pieces of carbon for arc lamps in a mortar. Prepare a similar powder from a natural chalk, better from calcium oxide. Weigh 8 g of calcium oxide and the calculated amount of carbon and thoroughly mix them. Spill the mixture into the inner pot of the arrangement and lower a second upper carbon electrode so that it almost contacts the first one. Connect a rheostat for 40 V. Switch on the current, which should be 10-15 A. Carefully move the electrodes apart, trying to obtain the maximum... 

The stirrer must provide good circulation if the temperature of th thermostat liquid is to be uniform. One design which is quite efficient and which occupies relatively little space is shown in Fig. 5-27. It is made from a length of brass tube to which supports have been silver-soldered at the top and bottom. A number of holes are drilled in the sides of the tube, and a central rod is fastened to the assembly. As this is turned (usually at — 1,500 to 1,800 rpm), centrifugal force throws the water out of the holes on the side. The supply of water is replenished through the top and bottom holes. The stirrer requires considerable torque for its operations, and it is usually necessary to employ at least a i/oo-hp motor. 

Fig. II, 56, 6 is a simple distillation head when this is fitted into a flask with a ground glass socket, the assembly is virtually a distillation flask. The bottom cone is usually 19, 24 or 29 the side cone is generafly B19 but may be 24 the thermometer socket is 14. For many purposes, a thermometer is fitted into a one-hole rubber stopper of correct taper and then inserted into the 14 socket the area of rubber which is exposed to the action of the organic vapour is relatively so small that the amount of contamination thus introduced is negligible. If, however, all rubber stoppers must be absent because of the highly corrosive character of the vapour, a thermometer with a 14 cone is employed. It is important to have the thermometer of the same glass as the distillation head, otherwise difficulties may arise owing to the different expansion coefficients of the two kinds of glass.

The apparatus illustrated in Fig. 3 is assembled, in a large hood if possible (Note 3). A is a 5- . round-bottom flask heated by a large ring burner and provided with a specially treated four-hole cork stopper covered with tin foil (Note 4). To these holes are fitted the column Z), the tube B reaching to the bottom of A, the specially bent tube C reaching up the inside of D, and the tube K connected with the tubes leading to the 2-I. separatory funnel H, so that the distance between the stopper of A and the stopcock of H is at least 100 cm. The bottom of the column D is of 20 mm. bore while the main portion is 30 mm. The side arm should be at least 85 cm. above the stopper of 4. The tube C... 

Cross-section flow area, minimum, of down-pipe clearance area between tray floor and down-pipe bottom edge, or up-flow area between outer circumference dotvn-pipe and any inlet tray w eir, in. Individual hole area per hole on sieve tray, in. Riser inside cross-section area per riser, in. Reversal area per cap assembly, in. ... 

When a hole has been bored from top to bottom of the coke bed, the boring tool is removed. It is replaced by cutting nozzles that are horizontal, so that the water jets penetrate and cut the coke bed. The nozzles are offset so the reaction rotates the nozzle assembly. The jets cut the coke bed into layers as the revolving jets move through the bed. The coke breaks away and falls to the bottom of the chamber. The diameter of the effective cutting stream is about 1.75 inches at a distance of 8 feet from the nozzle. The jets clean all of the coke from the chamber, so that it is not necessary for a man to enter the chamber at all. Furthermore, the action is fast over 150 tons of coke have been removed from a drum in 2 hours (12). 

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