Pioneering MUD RECOVERY SYSTEM Successfully Controls “Frac Outs” for Horizontal Directional Drilling projects

Ron Halderman, PE

Director HDD Division

Mears Group Inc

North American Society for Trenchless Technology

(NASTT)No-Dig Show 2011

Mears has developed a proprietary, patent pending Mud Recovery System (MRS) in order to reduce the risk of inadvertent returns (frac outs) and to extend HDD drilling lengths.

Horizontal drilling efficiency is directly related to maintaining constant and continuous drilling fluid “returns” along the drilled path back to the entry point

These advantages are essentially gained by collecting returning drilling fluids at a lower elevation along the drilled route by the use of internal and external submersible pumps, as illustrated here.

(1) 36” to 42” conductor casing; (2) 12”+ centralized guide casing; (3) 5” to 5.5” drill pipe; (4) external mud collection pipe; (5) external pump; (6) 14”+ casing for internal submersible mud pump

Primary components of the MRS:

• The MRS can be used from a barge or fixed platform on the water in a “water-to-water” drill

• [or from “water-to-land” or from “land-to-water”],

• or in a more conventional “land-to-land” drill

-- If necessary a low-strength grout seal can be set at the end of the conductor casing to isolate the system from external sea or ground water

Case Study 1 – The basic operating concept for Mears’ Mud Recovery System was developed during a 5000’+ installation of 24” fpvc pipeline under the Raritan River near Sayreville-Perth Amboy NJ. The generalized geologic profile & possible bore profiles are shown below.

Pressure calculations suggested that a potential “frac out” into the rivers’ thalweg (low point) might be able to be prevented or at least mitigated by drilling from the right side of the drawing instead of from the designed entry on the left (possibly using “intersection from both sides” if necessary); however, as shown by the “green” data points, a significant probability of frac out still existed even by drilling from the Perth Amboy side.

• Mears’ solution was to run the mud recycling suction hose down to the end of the 42-inch casing, thereby relieving 20 feet of elevation head and an estimated 10-12 psi of hydrostatic pressure.

• This relief reduced some of the mud pressure under the low point of the river as hoped.

• Based on these observations Mears began work on a more integrated MRS.

Case Study 2 - Mears completed an HDD project in Gig Harbor WA very successfully using its Mud Recovery System. A 24-inch HDPE pipeline was installed in a water-to-water crossing under an historical “light house” sitting on a pristine sand spit and park. – An absolute prerequisite for the installation was

“no frac outs” in or near the park and lighthouse.

GIG HARBOR WAWASTEWATER TREATMENT PIPELINE PROJECT

OUTFALL EXTENSION

Fixed platforms for the HDD rigs and support systems were constructed at both entry and exit sites due to the 15-foot tides in this region.

This large vertical movement would have made conventional barges untenable.

Paper ID #

As a result of the tides and potential storm surges, the platforms had to be constructed from 45’ to 50’ above the sea bed.

The commensurate hydrostatic head associated with this elevation created an additional 30 psi of required lift to get the heavy returning drilling fluids (with entrained cuttings) all the way back up to the top of the platform to the recycling plant.

Pressure calculations showed that this additional 30 psi would very likely create a “frac out” condition at or near the light house.

By using the Mears’ Mud Recovery System, this additional 30 psi could be eliminated by capturing the fluids at or below the sea level and then pumping them up to the platform.

The combination of fixed platforms and the Mears Mud Recovery System resulted in a successful project with no “frac outs” and no weather-caused delays

Case Study 3 (in progress) – Mears was selected by Dominion Virginia Gas as the EPC prime contractor for the construction of 230kV, 600 MW underground transmission lines between its existing York Town Power Station in York, VA and a new Gaines Point Terminal Station in Gloucester County, VA.

A substantial portion of this project has been horizontal directional drilling across the York River (total drilled distance of about 34,000 feet in three drill segments – each segment consisting of two parallel 8” lines separated by 15’).

North Drills approx 6000’ each (2)

Center Drills approx 7500’ each (2)

South Drills approx 3500’ each (2)

INITIAL PRESSURE CALCULATIONS

RISK REDUCTION PLANNING

• Use of fixed platforms (instead of barges) to limit weather delays and facilitate smooth transfer of work load between HDD contractor and electrical contractor

• Use of Gyro steering as primary program to improve accuracy in tight ROW

• Use of MRS as needed to stabilize borehole, limit amount of barged consumables, reduce fresh water requirements and control frac outs

Potential Uses for MRS technology

• Levees – the MRS can substantially reduce the hydrostatic head under the levee thereby greatly reducing the risk of destabilizing the levee.

• Shallow bedrock - the MRS could be used to allow the drill to be performed without drilling in the bedrock in areas where there is a high potential for frac-out due to the limited depth of cover.

• Long drills – the combined use of the MRS and intersect technology will contribute to regular planning and design of 10,000’+ HDDs.

• Environmentally sensitive areas – the MRS will provide a lower-risk scenario for crossing under wetlands, pristine water bodies, and in urban locations.

• ???

Trenchless Technology advances on the heels of innovation.

New steering technologies in the late 80’s produced a leap in applications due to improved accuracy.

MRS technology can produce a similar leap in applications due to environmental sensitivity.

Pioneering MUD RECOVERY SYSTEM Successfully Controls “Frac Outs” for Horizontal Directional Drilling projects

QUESTIONS?Ron Halderman, PE

Director HDD Division

Mears Group Inc