To control the kick whilst a heavier drilling mud is mixed, it has been decided

Question

To control the kick whilst a heavier drilling mud is mixed, it has been decided to circulate the rock chippings from the bottom of the hole to surface (circulate bottoms up) so that the wellsite geologist can establish if any change in the rock formation has occurred, then to spot a heavy pill at the bottom of the well (5500 ft) to try to stop the well from kicking. Calculate How many pump strokes are required to circulate bottoms? (ii) (b) How long will this take at a pump rate of 70 strokes per minute? (c) How many barrels of mud will be required to chase up the heavy weight mud pill and place it at the bottom of the well? (ii) How many pump strokes will this require? (i) How long will this take at a pump rate of 70 strokes per minute? Jack up rig Riser OD 21 Riser ID 19.75 30ft from sea level to rotary kelly bushing sea level 150t from sea level to sea foor seafloor Drill pipe: OD: 5 D:4.276 TD af casing 5000 ft Casing OD 18.58 D 17.75 Open hole OD 13.75 TD of Open hole 320 Bottom hole assembly 150ft in length OD:7 ID: 3.5" Standad Tricone bit OD:13.75 Figure Q2 Schematic diagram showing the offshore operating profile and drilling current status Additional information Calculate annular capacity in bbls/ft (ID2 OD 1029.4 where ID is the inside diameter of the riser, casing, open hole or drill pipe (in inches) OD is the outside diameter of drill pipe (in inches) Pump details: Triplex pump, 0.98 efficiency factor, liner size 6", stroke length 12", and maximum strokes per minutes is 70 Triplex pump output in bbl/stroke e0.000243 (Ld) where (SL) e is efficiency factor, Ld is liner diameter in inches, SL is stroke length in inches.

Explanation / Answer

b(i) Annular capacity(bbls/ft)=(ID2-OD2)/1029.4

    ID=19.75+ 4.276 + 17.75=41.776

OD=13.75

Annular capacity(bbls/ft)=1.5117

(ii) Triplex pumpout in bbl/stroke=e*0.000243*(Ld)2*(SL)

Triplex pumpout in bbl/70=0.98*0.000243*6*12

Triplex pumpout in bbl = 1.2002.

                                            

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