T-type drilling is a type of ultra-short radius drilling that can achieve 90 degree turns over sections as short as 2.1 meters using flexible drill pipe, resembling a "T" shape. It involves setting a whipstock at the planned depth and angle, milling a window, building curves up to the designed angle with flexible drill pipe, and drilling the lateral wellbore to total depth. The first offshore T-type drilling operation successfully drilled 4 lateral bores totaling over 60 meters in length off a parent well in the Weizhou 12-2 oilfield, significantly increasing production from 230 to 1400 barrels of fluid and 85 to 550 barrels of oil.

1. Crest Technology
T-type drilling
 Multilateral
 Ultra-Short Radius drilling
 Flexible Drill string

2. T-type drilling is a kind of USR (Ultra-Short Radius)drilling, The curve build up
rate is 90 degree per 2.1meter with flexible drill pipe. Which looks like a
“T”shaped drilling.
Flexible drill pipe
What is T-type Drilling
Drill 2.1m to Reach 90°
Drill 600meter to Reach 90°

3. Datas of T-type drilling：
 wellbore diameter is large: 6”;
 length 60~80m (record--115m)
 Sidekick wellbore casing 5-1/2”7”& 9-5/8”
 Kickoff in openhole (depends on the formation stability)
T-type Drilling Features
Maximum angle 105°
 Bit size 6”(152mm) ;
 Flexible drill pipe size 138mm
 length 60~80m (record--115m)
 Sidekick wellbore casing 5-1/2”7”& 9-5/8”
 Kickoff in openhole (depends on the formation stability)

4. Features of T-type drilling：
 Multilateral (can kickoff another
hole of different or same azimuth
every 2m of MD)
 The wellbore can be
designed/drilled to desired
direction. (not adjustable during
the drilling operation)
T-type Drilling Features
1st whipstock to kick of
the 1st lateral
Set the 2nd whipstock to
kick of the 2nd lateral

5. 1)Drift and Wellbore cleaning
T-type Drilling Standard operation procedure
2) Run whipstock with Gamma Ray &
Gyro @ the planned depth and tool face
( use MWD if the inclination is higher than
40°) ；
3) Pressure setting the whipstock in place;
pull out Gamma Ray and Gyro;
4) Mill the casing out, then pull out the
milling tools

6. 5) Build up curves with flexible drill pipe to the
designed angle and then pull out. If run a curve of
π/4, length, then the angle is of hole is 90°
T-type Drilling Standard operation procedure
6) Run in drill BHA with flexible drill pipe to TD;
* the flexible drill pipe for drilling and for build up curve is different

7. T-type Drilling Standard operation procedure
6 Plus) Run the Memorable trajectory
measuring tools with flexible drill pipe to TD;
then pull and measure the trajectory of the
hole. Read the data after POOH.
*Based on the drilling history, the trajectory
is quite accurate, the trajectory will be located
in a 1m radius circle after 100meters drilling.
Memorable trajectory measuring tools
Measure the trajectory
(if needed)
Time depth Inclination
Gravity
high
side
Gravity
vector Temperature
Battery
voltage

8. T-type Drilling Standard operation procedure
7) Flexible screen/slotted casing/drilled hole casing or: just open hole completion;
Flexible Screen

9. T-type Drilling Standard operation procedure
8) Run the 2nd whipstock just stacked on the
first one, and then pull out of hole
9) Run mill tools to kick off casing; pull out
of hole
10) Run curve build up flexible drill pipe
BHA; pull out of hole
1st whipstock to kick of
the 1st lateral
Set the 2nd whipstock
to kick of the 2nd lateral

10. T-type Drilling Standard operation procedure
11) Run recovery fishing tools to recover the whipstock (or leave it in down hole)

11. T-type Drilling Features
Advantages of flexible drill pipe USR sidetrack:
① Access Reserves Near Vertical Wellbore
② Sidetracks from vertical wells in Tightly Spaced Fields;
③ Sidetracks from vertical wells with water coning;
④ Sidetracks from Vertical wells with Near Wellbore Damage ;
⑤ Sidetracks into Channel Sands with Surrounding Shale;
⑥ Sidetracks from water injectors to Increase Injection Rates and improve Sweep Efficiency;
⑦ Exploitation of Attic Oil From a Vertical or Horizontal Wells;
⑧ Exploitation of Slim Hole Vertical or Horizontal Wells;
⑨ To Increase Injectivity and Deliverability in Gas Storage Reservoirs;
⑩ Replace Perforating; Acidizing & Fracturing a well
⑪ Use Lighter Workover Rigs and Smaller Circulating Systems
⑫ Low Lost in Hole Cost

12. 2018
Drilled the first well
offshore with 4 holes
The Flexible drill pipe USR was first
launched in early 2000. Since then, it has
drilled more than 100 wells onshore
T-type Working History
2019
Drilled the first well on submersible drill
ship under high wave weather condition
successfully with 3 holes.
2000

13. T-type Drilling Onshore working cases
Item
Well
Number
Inclina
tion
Formation lithology
and Depth（m）
Permeability
（Md)
Thickness
（m）
Purpose
Number of
holes
×length
(n×m)
Production
before
operation
（BBL）
Total & Oil
Water cut %
Production
before
operation
（BBL）
Total & Oil
Water cut %
1
Luo—S45-
26
30°
Fine Sandstone
1808.1-1826.0 1.9 17.9
Low permeability,
increase drainage
exposure
2×30
0.3×0.2
21.4%
3.2×2.6
20%
2 Jin93-32 50°
Sand stone
2898-2901.4 62.13 3.4 Exploitation attic oil 1×30
6.2×4.3
30%
13.6×10.6
22%
3
Honghe10
1
Vertical
Fine Sandstone
1922-1930.7 1.33 8.7
Low permeability,
increase drainage
exposure
1×100
/1×50
1.4×0.5
64%
4.5×2.5
45%
4 Ba111 21.6°
taxichnic dolomite
1754-1760 7.8 6
Sidetrack from vertical
well with water coning
1×70
6.2×1.1
83%
8.6×6.8
21%
5
Min49-
013
Vertical
Sand stone
1174.8-1180.2 5.6 5.4
Low permeability,
increase drainage
exposure
1×100
1.2×0.7
42%
7.3×3.7
50.1%
6
Tahe
TK766
Vertical
limestone
5545~5500 Exploitation attic oil 1X89.6m NA

14. Item
Well
Number
Inclina
tion
Formation lithology
and Depth（m）
Permeability
（Md)
Thickness
（m）
Purpose
Number of
holes
×length
(n×m)
Production before
operation（BBL）
Total & Oil
Water cut %
Production before
operation（BBL）
Total & Oil
Water cut %
1
First
well
offshore
Weizhou
WZ12-2-
B27
37°
argillaceous sandstone
2239 ~ 2269.0 （MD）
47.1 2~3m
Exploitation of
the thin
reservoir
1×62.5
1×31.3
1×26.1
1×34.5
New drilled
pay zone
410×350
×85%
2
Enping
EP23-2-
A1
64°
argillaceous sandstone
2622 （MD）
1653（TVD）
55 3m
To mitigate the
near wellbore
damage,
expand the
drainage
exposure
1×60.52
286.2×121.2
×58%
1418.9×605.6
×57%
3
First
well
submers
ible
Liuhua
LH11-1-
D05P1
45.6°
biohermal limestone
1520（MD）
0.01~9329，
(average
651mD)
8.7
Exploitation of
Attic Oil
1×8.7
1×73.1
1×74.5
4253×16
×99%
7520×71
×99%
T-type Drilling offshore working cases

15. Huabei oil field
Jin93-32 T--type drilling
Operation：06th –11th , June 2018
T-type Drilling Onshore working cases

16. Data
Layer
SN
Top of layer
Bottom of
layer
Thickness Porosity permeability oil saturation
130 2873.6 2883.6 10 20.22 47.31 61.44
131 2889.2 2890 0.8 14.76 11.82 0
132 2890 2893.6 3.6 20.94 55.13 62.91
133 2895.4 2896.6 1.2 18.8 34.34 44.39
134 2898 2901.4 3.4 21.51 62.13 58.8
135 2903.2 2908 4.8 21.16 57.8 64.63
136 2913.4 2917 3.6 20.19 47.01 53.73
137 2917 2921.2 4.2 15.91 16.48 31.25
138 2928 2932.4 4.4 16.22 17.93 63
140 2954.0 2956.6 2.6 14.5 10.80 7.3
Jin 93-32 logging Curve
T-type Drilling Onshore working cases
Kickoff point 2898m
Inclination 50 °

17. Exploitation of
the attic oil
T-type Drilling Onshore working cases

18. T type
drilling
Layer
SN
Depth
Top/bottom
Of layer
(m)
Thickne
ss
(m)
Kick off
Point
(m)
Kick off point
inclination (°)
Kick off point
Azimuth (°)
Inclination
of the pay
zone (°)
Planned
depth (m)
134 2898/2901.4 3.4
2898 50.82 291 22 30
Jin93-32 T type hole data
T-type Drilling Onshore working cases

19. WhipStock
T-type Drilling Onshore working cases
Operation sequence
（1）Set the Whipstock@ the
planned depth and azimuth
（2）kickoff and mill the window
（3）Build up curves
（4）T type drilling to TD
（5）Retrieve the Whipstock

20. T-type Drilling Onshore working cases
Run in Milling shoeOperation sequence
（1）Set the Whipstock@ the
planned depth and azimuth
（2）kickoff and mill the window
（3）Build up curves
（4）T type drilling to TD
（5）Retrieve the Whipstock

21. Operation sequence
（1）Set the Whipstock@ the
planned depth and azimuth
（2）kickoff and mill the window
（3）Build up curves
（4）T type drilling to TD
（5）Retrieve the Whipstock
T-type Drilling Onshore working cases
Before run in Hole

22. Run curve built up BHA:
(D114mm PDC bit + Flexible drill pipe 3.81m)
Depth: 2898.62m,
Mud density: 1.02g/cm3 , Viscosity37s
Pressure: 9-10MPa，
Circulation : 400L/min,
WOB: 20-30kN，
ROP: 20-30r/min，
Penetration: 1.60m (2898.62m to 2900.22m,)
Pull up 3m，circulating: and get fine sand Curve built up BHA POOH
T-type Drilling Onshore working cases

23. Operation sequence
（1）Set the Whipstock@ the
planned depth and azimuth
（2）kickoff and mill the window
（3）Build up curves
（4）T type drilling to TD
（5）Retrieve the Whipstock
T-type Drilling Onshore working cases
Run in Hole of drilling BHA

24. The drilling BHA:
(D114mm PDC bit + D102mm Flexible drill pipe
35.61m)
Depth: 2898.62m,
Mud density: 1.02g/cm3 , Viscosity37s
Pressure: 9-10MPa，
Circulation : 500L/min,
WOB: 20-50kN，
ROP: 40-80r/min，
Penetration: 30.1m ( 2900.22m to 2930.32m,)
Pull out of the Drilling BHA
T-type Drilling Onshore working cases

25. Operation sequence
（1）Set the Whipstock@ the
planned depth and azimuth
（2）kickoff and mill the window
（3）Build up curves
（4）T type drilling to TD
（5）Retrieve the Whipstock
T-type Drilling Onshore working cases

26. T-type Drilling Onshore working cases
Total length of wellbore 30.1m，
formation inclination angle 22°
Azimuth 291°
Kick off point
2898m
Schematic of the Well
Totally 6 days used
from the first run
of whipstock to
retrieve the
whipstock

27. Weizhou12-2-B27
T type drilling
T-type Drilling offshore working cases

28. Weizhou 12-2oilfield
Weizhou12-2oil field locates West Part of South China Sea
T-type Drilling offshore working cases

29. T-type Drilling offshore working cases
Lithology of the oil field
Weizhou 12-2 oil field is a fault trap. The purpose of the operation is
to exploitation of the some thin layer of pay zone

30. Logging data
T1
T2
T3
T4
T-type Drilling offshore working cases

31. Schemetic f the T-type drilling
Hole
Pay zone：L2Ⅱa-b Depth of sidetrack
Length of
hole
TOP of layer
Bottom
of layer
thickness depth Inclination Azimuth Tool face
T1 2774.40 2779.30 4.90 2774.5 36.7 40.3 R10° 62.5
T2 2756.00 2760.40 4.40 2755.93 37.2 40.5 0° 31.30
T3 2738.80 2745.20 6.40 2739.45 37.5 40.3 0° 30.55
T4 2774.40 2779.30 4.90 2741.54 36.7 40.3 0° 34.45
T-type Drilling offshore working cases

32. Branch T1 Operation 校深定向
Weizhou 12-2-B27 T type drilling

33. Whipstock POOH
Whipstock RIH Curve build up BHA RIHMilling Shoe RIH
Weizhou 12-2-B27 T type drilling
Milling Shoe POOH Curve build up BHA POOH

34. Flexible drill pipe before RIH
slightly worn after POOH, with the highest torque 37000 lbs.ft.
Weizhou 12-2-B27 T type drilling
Flexible drill pipe after POOH

35. Weizhou 12-2-B27 T type drilling
Celebration of the first offshore T- type drilling operation

36. One hole, 60meter. The production increase….
二、T型钻孔技术的发展—海上案例
T-type Drilling offshore working cases
Fluid production 230bbl ---1400bbl Oil Production 85bbl ---- 550BBL

37. T-type Drilling offshore working cases
Successful T-type drilling Celebration

38. Crest Technology
contact: Guozhonglei@gmail.com