A well-known oil company in Argentina transports products from one of its refineries located in the Andes foothills to its principal markets in Buenos Aires. A pipeline stretching some 1,700 km transports the company’s products to their destination. When routine inspection revealed compromised technical integrity of a pipeline section, the decision was made to replace the affected section.
However, the section passed through a heavily flooded area, which complicated the replacement effort. The project called for the HDD installation of 5,800 ft of heavy, 14-in. pipe beneath a large body of water renowned for its abundant fisheries and populous public park areas. Needless to say, stringent environmental precautions were mandatory.
Flowtex HDD S.A. was awarded the contract for executing this extended and complex crossing. Efficient management of the drilling fluid’s component was fundamental in complying with a limited time constraint to complete the crossing due to the rapidly escalating COVID-19 pandemic.
After a thorough analysis of soil conditions and probable weather situations, the desired drill path and tool set were defined. Water quality analysis showed a high magnesium salts content in the lagoon, as well as in the water table on rig side. Consequently, clean fresh water was piped in from the opposite shore by means of a temporary duct laid on a nearby highway overpass.
A sturdy American Augers 440,000-lb, horizontal directional drill rig was the basic equipment chosen for the crossing. The fluid setup on rig side was essential to meet the short timeframe and comply with the strict environmental limitations. Fluid was pumped down hole by a housed, standalone Triplex pump fed from a 15,000-gallon buffer tank into which fresh and recycled fluids were joined for mixing. A 12,000-gallon double tank, fresh fluid makeup plant was located next to the elevated materials handling and storage area. Materials were fed into the first section of this system from a sack table that fed into a high-power venturi hopper, impelled by a 6×5 60 HP pump. Strong mixing was achieved in both sections equipped with elephant foot rotating nozzle mixers.
Mud returning with high solids content was pumped from the start pit to a mud recycling system that had been recently upgraded by replacing the original mud system shakers with two Derrick Hyperpool shakers. The shaker replacement was required since the original shakers could neither consistently process returns from the drill nor provide the desired cleaning performance. These deficiencies led to reduced production and increased operating costs.
To develop a strategy for the drilling operation, in 2018, Derrick technical service engineers collaborated closely with the team from Flowtex HDD S.A. The conclusion was to upgrade the mud system with high-performance linear motion Hyperpool shakers. In addition, the hydrocyclone circuit would be upgraded to achieve the required pressure at the desilter header. Derrick’s recommendations included upgrading the centrifugal pumps and plumbing to achieve sufficient hydrocyclone pressure for optimal separation. This upgrade would also ensure maximum solids removal at the final stage of separation, allowing cleaned fluid from the cones to ultimately be pumped back downhole. Any coarse, sand-size and larger particles still remaining in the drilling fluid at this point would have major detrimental effects on the operation. These coarse particles would contribute to excessive wear and damage to downstream equipment, increased non-productive time (NPT), increased torque and drag on the drill string, increased chances for hydraulic fracture of the formation, and other harmful effects.
The upgraded mud system was designed around one Derrick Hyperpool shaker, a four-panel high G linear motion shaker outfitted with Pyramid screen panels for the primary separation of the raw mud. To reduce the burden on downstream separation equipment and minimize the amount of fine partial attrition, the screens on the initial separation had to be as fine as possible. To meet this requirement, Pyramid screens in the API 70 to 100 range were installed on the primary shaker. The underflow fluid from this shaker reported to a 2,000-gallon primary (dirty) tank. A 50 HP Derrick Premium 250 centrifugal pump was used to pump the mud from the tank to an inline 10-cone desilter with 4-inch hydrocyclones having a d50 cut point of 15 to 40 μm. Dewatering was accomplished by a secondary Hyperpool shaker with finer Pyramid screens in the API 170 to 200 range. Cleaned fluid from the hydrocyclones was plumbed to the 4,000-gallon clean tank located below the shaker.
All dry solids from the two Hyperpools were directed into removable bins for disposal. The clean fluid would either flow into the primary tank or was fed to a buffer tank for re-utilization. This setup was capable of keeping pace with the 350- to 400-gpm pumping rate during construction of the pilot hole and 450- to 500-gpm flow during reaming.
Great precision was required for the punch-out section, as the new drill path paralleled the existing live pipe at a distance of less than 6 ft. Once the pilot hole was completed, a single shot ream was used to enlarge the bore to 24 in.
By this time, 6,000 ft of steel pipe had been welded, tested, dressed, and laid on rollers stretching straight back from the exit point. The pipe was taken up through a towing head welded on front, a swivel, and appropriate shackles. After final positioning, the column of pipe was pulled through a swan neck down into the tunnel. The hole was clean, straight, and flooded with fluids of correct density; the pulling force remained under 20 tons.
The Hyperpool shakers and innovative Derrick screen technology made a dramatic improvement in the drilling operation. The new Hyperpool (high-G recycler) with Pyramid screens proved to have a voracious appetite for waste cuttings, assuring a stable downhole within a spotless environment.
Material consumption was greatly reduced, and pump maintenance during the operation was unnecessary. The continuous flow of clean drilling fluid, when needed, contributed strongly to a 25 percent reduction in the anticipated overall job completion time. The complete job from rig up to rig down took only 19 days.