The BU-W02 development well was drilled from the BU-WP1 platform by ENSCO 104 jackup rig. BU-WP1 is located in the eastern half of the Bayu-Undan gas condensate field which is in the Production Sharing Contract (PSC) areas of JPDA 03-12 and JPDA 03-13, North Bonaparte Basin, Timor Sea, offshore Northwest Australia. The location is approximately 25km south of the production facilities of Elang oil field and 480km northwest of Darwin. ConocoPhillips (91-12) Pty Ltd is the operator.
The Ensco 104 jackup drilling rig was on location on 15th May 2002 in 78.3 meters (LAT) of water depth and rotary table elevation of 45.4 meters above sea level. All depths are referenced to the Ensco 104 Rotary Table unless otherwise indicated. BU-W02 was spudded in on 25th May 2002, as part of batch drilling procedures with 5 other well. The well was drilled to the east and reached a total depth of 4697 mMDRT in 12 ¼" hole size on 13th November 2002. Hole instability problems resulted in BU-W02 being plugged and abandoned with two cement plugs between 2950-2801 mMDRT and 2801-2735.3 mMDRT respectively. An 11 ¾" liner was run and cemented at a depth of 2732.3 mMDRT.
BU-W02ST1 kicked off from a depth of 2740 mMDRT, on the 3rd December 2002. The W02-ST1 well reached a total depth of 4986 mMDRT in 8 ½” hole size using Oil Based Mud (LTOBM) on 28th December 2002. The well was cased and completed with 166 metres of net sands to be perforated as a condensate and gas producer.
SAMPLES, SIDEWALL CORES CONVENTIONAL CORES
Drill Cuttings
BU-W02
Ditch cuttings spot samples were collected at 5 or 10 m intervals in the 17 ½" hole section between 807.0 and 2413.0 mMDRT. Composite washed and unwashed ditch cuttings samples were collected for storage at 5 or 10 m intervals in the 12 ¼" hole section, between 2413.0 and 4697.0 mMDRT. A ditch cuttings sampling summary is listed in Table below.
BU-W02 Ditch Cuttings Sampling Type and Frequency
Interval mMDRT | Sample Frequency | Sample Type | Distribution |
| 2740.0 to 3200.0 | 20 m | Washed & Unwashed | Unwashed: ConocoPhillips 1 set East Timor Gov’t 1 set Washed: ConocoPhillips 1 set East Timor Gov’t 1 set Geoscience Aust. 1 set |
| 3200.0 to 3240.0 | 10 m | Washed & Unwashed | |
| 3240.0 to 3520.0 | 20 m | Washed & Unwashed | |
| 3520.0 to 3600.0 | 10 m | Washed & Unwashed | |
| 3600.0 to 4520.0 | 20 m | Washed & Unwashed | |
| 4520.0 to 4580.0 | 5/10 m | Washed & Unwashed | |
| 4580.0 to 4690.0 | 20 m | Washed & Unwashed | |
| 4690.0 to 4985.0 | 5 m | Washed & Unwashed |
Cores
No conventional cores were cut.
Sidewall Cores
No sidewall cores were acquired.
LOGGING AND SURVEYS
Mud logging
Sperry-sun Drilling Services provided the mud logging services with formation evaluation and pressure monitoring services from 123.7 mMDRT to total depth. Drilling rate, calcimetries, lithologies, total gas and chromatographic analysis of the ditch gas are plotted on the mudlog. Pressure indicators were measured and are plotted on the pressure log.
LWD Logging
BU-W02
Sperry-sun Drilling Services ran the open hole LWD logs that are summarised in Table.
Run | Hole
Size | Tool
String | Interval
(mMDRT) | Comments |
| 400 | 17½” | DDS-GR-PWD | 807-1533 | Pulled out of hole at 1533 mMDRT after drawworks brakes failed causing string to drop |
| 500 | 17½” | DDS-BAT-GR-PWD | 1533-2133 | Some shocks registered on DDS while rotating with AGS open. |
| 600 | 17½” | DDS-BAT-GR-PWD | 2133-2419 | DDS registering shocks especially while drilling with AGS open and backreaming. |
| 700 | 12½” | GR-PWD-BAT-SLD | 2419-2419 | Failure due to fluid invasion into the connections between the pulser and the probes as a result of missing o-rings in the pulser. |
| 800 | 12¼” | DDS-GR-PWD-BAT-SLD | 2419-2882 | Failed whilst backreaming to shoe. Pulser severely damaged and jammed with debris from teflon spacer and rubber spacer washed out from top of SLD |
| 900 | 12¼” | DDS-GR-PWD-BAT-SLD | 2882-4697 | Due to excess rotating/backreaming without circulation, the SLD tool was damaged and data could not be obtained from the tool's memory. |
| 1000 | 12¼” | DDS-GR-PWD | 4697-4697 | Cleanout run. |
Wireline Logging
All logging was acquired in cased hole. CGG were used to acquire velocity VSP/Checkshot
data in BU-W02 in cased hole on a Halliburton Logging Services (HLS) wireline cable.
Suite | Run | Tool String | Interval (mRT) | BHT/Hrs Since Circ. | Comments | ||
| BU-W02 | |||||||
1 | 1 | CGG Vertical Incidence Checkshot | 770-123 |  | Dual BSR-4 geophones run at 30m interval (flexible bridle). Tool hung up at 772m. | ||
2 | 1 | CGG Vertical Incidence Checkshot | 2349-660 | | Checkshots at 1030 mMDRT, 1510 mMDRT and 2140 mMDRT on way in hole. Tool hung up at 2350m. | ||
| BU-W02ST1 | |||||||
1 | 1 | CGG Vertical Incidence Checkshot | 4939-2170 | | Check levels not shot below 3080 mMDRT due to high angle below this depth. Two attempts required to run tool through top of liner PBR. Tool pickup depth was 4939 mMDRT. | ||
2 | 1 | CBL-GR-CCL | 4938-4484 | | Main pass logged with 1000psi. Tool string lost in hole upon reaching surface. | ||
2 | 2 | CCL-Impression Block | 4528-4482 | | Fish finding run. Tool held up in completion string before fish tagged. | ||
2 | 3 | CCL – Compact Tool String | 4926-4799 | | Fish finding run #2. Fish tagged with lead impression block at 4926m. | ||
2 | 4 | CAST-GR-CCL | 4923-4474 | | Main pass logged with 1000psi | ||
2 | 5 | Wireline Fishing Overshot Assembly | | | Fish tagged at 4926m. No visual damage to the fished CBL tool string | ||