In November 2021, Conveca Peru was able to finish the longest HDD Drill in the history of Peru. The crossing of the Rio Chira in Paita, Piura, Peru is part of the Gasoducto GASNORP Pipeline and ensures the energy supply of many north Peruvian households.
In collaboration with BM Drilling Services, an engineering and operational HDD services company, a 6-in. HDPE conduit and a 10-in. gas pipeline were installed over a total length of 2,000 m each. The long distance, the soft geology (sand and clay) and the tight timetable under COVID-19 restrictions resulted in additional challenges for Conveca and BM Drilling Services. To face these challenges the crew took several precautions:
Precaution 1: Selecting a powerful machine with enough pull force and additional torque
The drill was carried out using a Herrenknecht 300-tonne (660,000-lbs) rig. To be prepared for the torques, that are increased with the length of the drill, Conveca upgraded the torque of the rotary drive from 90 kNm (66,000 ft lbs) to 120 kNm (88,500 ft lbs).
Precaution 2: Constant monitoring of the downhole pressure
With soft ground conditions also comes a high risk of inadvertent returns (frac-outs) due to poorer ground stability. Therefore, Conveca assigned the French based engineering company Optimum to carry out geological studies with hydrofractural calculations. They measured the solidity of the ground and calculated the possible downhole pressure for each drill pipe. With a downhole pressure module, which was placed in the downhole assembly directly in front of the guidance probe, the crew constantly monitored the stability of the bore hole and compared it with the permitted data provided.
Precaution 3: Lightweight downhole assembly
To avoid the drill bit sinking in the soft ground, Conveca used a modified and lightweight downhole assembly with an outer diameter partially reduced from 8 to 6 in.
Precaution 4: First use of a new HDD casing type
The record-setting length of the crossing and the sporadic soft ground conditions especially within the entry section made the application of a casing one of the main requirements for this drill. Casing operations are usually used to reduce the risk of frac-outs and to prevent twist-off of the drill pipe. Under consideration of the tight timetable, and for the first time worldwide, Conveca decided to use the new 16-in. Titan HDD casing from International Drilling Services Ltd (IDS). The casing is equipped with a special quick connect/disconnect coupling system, which reduces the assembly time of the casing pipes to approximately five minutes per joint — a huge improvement when reconsidering the time-consuming connection of traditional threaded or field welded casings.
Precaution 5: Use of a hybrid drill string
The high push forces increasing with the length of the crossing can also result in a greater risk of higher bend of the drill string. This load pushes the drill string to the bottom or top rim of the borehole and leads to additional fractures of the borehole. The described behavior may cause additional frac-out risk and sinking of the whole drill string. To counteract the bend, avoid a misalignment from the marked-out route and a buckling of the drill string, Conveca increased the diameter of the last 50 drill pipes from 6 5/8 in. to 7 5/8 in. to make the section of the string stiffer where there is the highest risk of buckling and bending.
Precaution 6: Weeper subs with horizontal directed nozzles
With the increasing length of the drill, it is more difficult to clean a borehole. On the bottom of the borehole, sedimented cuttings are blocking the returns in the ring annulus. To increase the return flow, weeper subs with a horizontal jet alignment were installed in the drill string. These weeper subs are equipped with TC jet nozzles to accelerate the return flow and clean the borehole again.
“Conveca´s philosophy when buying equipment was always to focus on quality over quantity, it always pays off in the long-term,” said Conveca owner Renzo Basso. “We think we have a very advanced HDD spread, with mostly German equipment and when we were looking to add a casing system to our spread, we searched for the best option and found the Titan casing. We always had a pioneer spirit with all the work Conveca did over the last 50 years, so we were happy to try the Titan casing as the first company worldwide after studying all other options.”
BM Drilling Services HDD superintendent Carsten Brueckner added, “I was never a big fan of casing operations because the existing solutions were built for other drilling scenarios. It was always a slow process and a little unpredictable. We never had a solution that was tested on the maximum pull force and torque figures. With the Titan casing we had the situation that, we know exactly where its limits are and fortunately those were the same as the capacity of our rig. Additionally, the fast and easy connection is a big plus over the other solutions. Half of our crew were locals who worked for the first time on an HDD rig and they did a great job running that casing”.
Good preparation and planning were the key for the success of the project. Thanks to all measures and the extensive commitment of the crew it was possible to finish the drill six days ahead of the schedule.
Project at a Glance
- Project: Gasoducto GASNORP – Cruce del Rio Chira
- Status: Both HDD crossings completed, 6-in. HDPE and 10-in. steel pipe installed
- Drilling Contractor: Conveca Peru SAC
- Client: Morelco/Cumbra
- General Contractor: Quavii
- Total drilling length: 4,000 m
- Length per crossing: 2,000 m
- TVD: 24 to 26 m
- Pilothole Diameter: 12-1/4 9-in. (311-mm)
- Tooling Pilothole: Milled tooth Tricone Bit on jetting BHA, IDS 16-in. Titan Casing
- Reaming Diameter for 10-in. pipeline: 18 in.
- Tooling Reaming: IDS-Hybrid Reamer
- Pipeline: – 1 x 6-in. HDPE SDR9 – 1 x 10-in. Steel
- Rig: Herrenknecht HK300T – upgraded to 120-kNm Torque
- Geology: Sand, Clay
- Guidance: Paratrack 2 + Pressure module
- Guidance Service: BM Drilling Services
- Type of Fluid: MI-Swaco, AMC
- Fluid Service: BM Drilling Services
Marco Fiedler works in communications at Herrenknecht AG. Carsten Brueckner is with BM Drilling Services. Gianpaolo Basso is with Conveca LLC.