July 1998 Vol. 219 No. 7  Drilling

J. John Grow,  Engineering Editor

Deepwater supply base makes good sense

One-stop-shopping deepwater facility just makes good sense — wonder why it hasn’t been thought of before. The C-Port deepwater facility in Port Fourchon, Louisiana, is a one-of-a-kind port, owned and operated by Edison Chouest Offshore of Galliano, Louisiana. It was built to handle massive vessels (about 177-ft long and 20-ft draft) needed to service burgeoning deepwater activity in the GOM.

This facility was designed to save deepwater vessels time in on / off loading of tubulars, water, fuel, mud and consumables by giving them the option of one stop vs. travel to different docks to accomplish the same goal. What takes a matter of days for a deepwater vessel can be done in hours. With extended travel time to and from deeper waters, C-Port deepwater facility is not only a convenience, it makes deepwater operations more economically feasible.

M-I has signed an agreement to be the ports exclusive drilling fluid supplier. Operations include a bulk barite facility, three liquid mixing and 18 storage tanks. Capacity is more than 27,000 bbl liquids and 72,000 sacks of bulk barite.

Steerable bit designs cut GOM drilling costs. A major problem associated with drilling directional wells with PDC bits on steerable motor assemblies is maintaining toolface orientation. This is often due to drillstring torque fluctuations caused by erratic weight on bit, and can result in general hole degradation. According to Hughes Christensen (HC), the keys to improved steerability and wellbore quality is proper toolface control and bit gauge aggressiveness. Friction effects are compounded by mechanical sticking of the drilling assembly on ledged or spiraled wellbores. Some wellbore problems are caused by bit vibration and drilling fluid interaction with the formation, but most result from steerable drilling assembly characteristics in slide and rotation modes.

An ideal steerable assembly would be able to maintain hole quality and toolface orientation with minimal torque fluctuations while maximizing ROP and matching actual to predicted build rates, which are essentially influenced by bit design. Common drilling perception is that a short, aggressive-gauge bit is required for steerability; however, as demonstrated through lab and fieldwork, this may be misguided.

The HC BlackTrax bit features application-specific, polished-cutter technology and engineered cutter placement, resulting in a highly steerable bit. Cutter aggressiveness is modified across the bit face to greatly reduce torque response to WOB changes without compromising ROP. Another important feature is a tandem gauge design that 1) retards wellbore ledging and spiraling by reducing side-cutting aggressiveness, and 2) provides a secondary reaming capability, insuring a quality wellbore. Two applications are noted here.

Matagorda Island, Texas. Amoco was able to build from 14.9° to 37.6° and turn from 319° to 34.7° with a 12-1/4-in. BX554 bit through shale / sand sections. This was a first in the Matagorda Island area with a PDC bit.

Mobile Bay, Alabama. Mobil’s objective for this 8-1/2-in. hole interval was to drill the entire build section through shale / sand formations. Offsets required nine bits to drill the build section between 16,799 ft and 19,789 ft, with total costs of more than $1.25 million. An HC 8-1/2-in. BX447 bit allowed the entire build section from 13,452 to 16, 330 ft to be drilled in a comparable shale / sand sequence using only two bits, at a total cost of $585,000. A combined bit cost, plus reduced drilling / tripping time, equaled savings of $668,000.

Alternative to pipe-conveyed intervention. Welltec’s Well Tractor offers a fast, cost-effective method for conveying well intervention equipment and tools into horizontal and highly deviated, extended reach wells.

Benefits of the alternative to standard pipe or coiled tubing-conveyed operations are short-rig up time, downhole speed and easy handling. Further, operations can be in live producing wells under extreme hostile HT/HP downhole conditions.

Operations have been performed in live oil producers with production rates up to 25,000 bopd, and a total running distance of more than one million ft has been accumulated. Horizontal wells to 9,400 ft, and deviated wells to 17,000 ft, have been tractored in a single run.

A wide range of wireline tools from various major service and manufacturing companies has been conveyed, including production logging tools, perforation guns, bailers, cement bond logs, plugs, fishing tools and neutron measurement tools.

Three different tool sizes are available: 2-1/8, 3-1/8 and 4-3/4 in. for operations in 2.2-in. to 13.4-in. ID tubing or openhole. Operations in which the tool has been used successfully include: sliding sleeves, setting and pulling plugs, running production and cement bond logs, drilling, milling, cleaning and running perforation guns. Applications in two types of wells are shown below.

Monobore water injector well. The tractor was used in combination with 7-in. production logging tools (PLT), in a 16,570-ft TD well with deviation of 93° at 14,435 ft. Maximum temperature and pressure were 122°F and 6,240 psi.

After the PLT string was RIH, the tool was activated at 13,120 ft and the PLT was tractored to 15,350 ft. The toolstring had to be pulled to clean the fullbore spinner assembly, which was full of sand and debris. On the next run, the PLT logging program was performed over three flow rates without problems. Accumulated horizontal running distance for this 8-hr job was about 9,800 ft.

Oil producer. Well data: TD 15,750 ft, max. deviation of 90° at 12,470 ft, maximum temperature and pressure were 200°F and 4,570 psi.

The tractor was activated at 9,840 ft and RIH to 15,160 ft. The perforated interval was logged at three different flow rates, with four logging passes at each rate. A caliper run verified casing ID and showed a scale buildup; it is suspected that excessive sand / debris prevented running into the last part of the horizontal section. Accumulated horizontal distance for this operation was about 18,000 ft.

In 1996, the first offshore testing of wireline driven downhole tractors took place through the combined efforts of Statoil A/S and Welltec, the Denmark-based tool developer.

Copyright © 1999 World Oil
Copyright © 1999 Gulf Publishing Company