199
D
-
(g5--gEOD)
COS& 2
True vertical depth f o r gEOD < g5 ~ gT" Ds
-
18 000
DKOP +
'
7rdl
sin (dl (gEOB -- (KOP) X 10 -2)
+(gDOP -- gEOB) COS a
18,000
+ ~ rrd2
(4.79)
1
sin (d2 (gEOD -- gDOP) X 10 -2) + (gs -- gEO>) cosa2
--
DDOP + R2 sin(c~l - a2) + (g5 -- gEOD) cosct2
=
DEOD + (g5 -- gEOD) COS&2
(4.80)
Thus, for a measured depth of 15,095 ft the TVD is" -
Ds
18,000
5 000 + '
sin 40 + (12,428 - 7 000) cos 40
71"2
18,000
=
+ ~ sin(40 - O) ~rl.5 13,455 ft
Similarly, for a measured depth of 20,638 ft the TVD is" Ds
-
13,455+(20,638-15,095)
=
18,998 ft
where: D g
= =
true vertical depth. measured depth.
= = = =
dropoff point. end of build. end of dropoff. kickoff point.
Subscripts: DOP EOB EOD KOP
A friction factor of 0.35 will be used to calculate the drag associated tension on the casing. The effect of friction on axial load during downward movement is ignored. For the buildup section, the tension load will be calculated by arbitrarily dividing this section into three equal parts: top, middle, and bottom. For the slant, and dropoff sections, the tension load will be calculated by considering each of tllem as one section. The approach to the buildup section is very arbitrary and not at all ideal, but this is an example of a hand calculation of a problem which can accurately be solved with a computer (Chapter 5 shows how).