Top hole – 24″ section
The top hole 24” section was drilled to 800 m. A Fracseal sweep pill program was run on the section, pumping 5 m3 pills with 35 kg/m3 at a frequency of 2 times per stand drilled. The section saw improved hole cleaning and the unconsolidated shales and high permeable sands on the section were successfully stabilized.

18.5″ section
The 18.5” section was drilled to 2,600 m, including a pressure ramp from 1,600 m to 2,500 m where the MW was increased stepwise according to a prearranged schedule from 1.15 SG to 1.50 SG. While drilling the mud was continuously treated with Fracseal F in the range of 5 – 10 kg/m3 concentration. This was done by mixing 30 m3 batches of premix with Fracseal concentration in the range of 15 – 30 kg/m3. A wiper trip performed at 1,611 m back to the 20” casing shoe, prior to entering the transition to HP drilling environment, confirmed the hole conditions to be good. After calling TD at 2,600 m and pulling out of hole, the liner became differentially stuck while connecting the liner hanger. After cutting the MW and freeing the string, a sidetrack was initiated at depth 2,423 m. The mud treatment with Fracseal was adjusted to 5 kg/m3 on the conditioning run ahead of the sidetrack and confirmed at rig site by testing.

Sidetrack
The sidetrack was drilled in slide- and rotary mode to 2,595 m for section TD. While drilling the mud was continuously treated with Fracseal by using a dedicated premix pit and a diaphragm pump to maintain the bridging treatment independently of any other mud treatment being made. The change was made to avoid any unnecessary and avoidable disruptions to the continuous treatment.

12.25″ interval
The 12.25” interval objective was to use Fracseal as background LCM to reduce the risk of losses while drilling through conglomerate formations and case this formation off for TD at the top of the reservoir. The contingency for the section if not able to achieve planned depth was to set 11 3/8” liner and drilled additional interval to top of reservoir. The hole was displaced from 1.85 SG WBM to 1.85 SG Versatherm OBM prior to starting operations on the 12.25 interval. Drilling the last quarter of the shoe track, the Fracseal concentration in the active was adjusted to 8 kg/m3 by bleeding in a 20 m3 pill with 113 kg/m3 Fracseal. After the shoe track was drilled and the hole circulated clean, a 5 m3 WBS pill with 42 kg/m3 Fracseal was spot on bottom for the planned LOT. The LOT was performed with a MW of 1.85 SG, applying surface back pressure at 104 bar and achieved a final LOT value of EMW 2.20 SG. A second LOT was performed and a new WBS pill spotted this time with 72 kg/m3 Fracseal concentration. The final LOT value achieved was 2.17 SG.

After performing the LOT, the DO BHA was POOH and the RSS drilling BHA was RIH for starting drilling operations on the 12.25’’ hole interval. The 12.25’’ interval was drilled with MPD system installed for holding constant BHP at connections. Starting MW for drilling the section was 1.85 SG. In advance of drilling operations starting, as contingency for losses, a 14 m3 LCM pill with 57 kg/m3 Fracseal + 28 kg/m3 CaCO3M, and a 14 m3 LCM pill with 100 kg/m3 Stoploss were mixed and kept on standby. While drilling, the background LCM was built into the active at a concentration of 10 kg/m3 Fracseal and maintained according to hole conditions and progress by continuously bleeding-in high concentration premix pills. Entering the conglomerates, the premix concentration was adjusted from 20 kg/m3 to 35 kg/m3 Fracseal to provide a more aggressive treatment strategy. The rate of transfer was increased from 3 m3/hr to 5 m3/ hr.

Drilling penetrated multiple high permeability sandstone layers on the section. The lower than expected LOT value at the 13 3/8’’ casing shoe at 2.20 SG resulted in a lower FG and a smaller drilling window. The MW was kept at just above the PP while drilling and dynamic pore pressure tests performed at regular intervals to evaluate gas levels and adjust MW. While drilling, in response to DPPT’s, the MW was increased from initial 1.85 SG to 2.11 SG at final section TD (3,630 m) with a PP at this point of 2.14 SG and an ECD of 2.17 SG (equivalent to the fracture reopening pressure at 13 3/8’’ casing shoe as confirmed by second LOT).

The wiper trip performed at section TD confirmed the hole conditions to be good with a tight spots recorded between 3,273 m to 3,600 m and reamed. At the 13 3/8’’ casing shoe, depth 3,018 m, a flow check was performed and confirmed static hole conditions with no recorded losses. Prior to running the 9 5/8’’ casing, Fracseal was screened out. The casing was run to depth 2,598 m where losses were observed at an initial rate of 200 ltr/hr. Just out from the 13 3/8’’ casing shoe at depth 3,038 m the gels were broken and a loss rate of 2,500 lpm was observed. A 15 m3 LCM pill with 57 kg/m3 Fracseal and 28 kg/m3 CaCO3 was pumped to fight the increasing loss rate. At section TD, circulation B/U was started at FR 400 lpm and increased to 800 lpm with no losses observed.

Ahead of the spacer for the cement job a 10 m3 LCM pill with 35 kg/m3 Fracseal was pumped as a cushion to minimize losses during the operation. The cement job was performed with no recorded losses.