Wired composite tubing yields time-lapse resistivity logging

April 22, 2002
Although commercial applications of composite coiled-tubing systems for drilling and well construction are limited, the work performed in test wells has yielded interesting results.

Although commercial applications of composite coiled-tubing systems for drilling and well construction are limited, the work performed in test wells has yielded interesting results.

The composite coiled-tubing system, which Halliburton calls the Anaconda Advanced Well Construction System, has drilled wellbores at a company facility in Oklahoma and in a test well for BP PLC, called the G.W. Craig No. 1, in Chocolate Bayou near Galveston, Tex.

According to Halliburton's information, the system has drilled 9,252 ft of 43/4-in. hole in the test wells, with the coiled-tubing running 1.3 million cumulative ft in the test wells and flow loops, and 1,950 hr total circulating time.

The openhole tractor has operated more than 50 hr in a single run.

The tractor has also walked 3,720 ft in 51/2-in. casing, 4,620 ft in 43/4-in. open hole, and it has walked through a 51/2-in. casing whipstock at 78° inclination.

Resistivity logging

Development of wired composite tubing enables the continuous acquisition of petrophysical and drilling dynamics data during drilling operations, resulting in logging passes for each bit trip.

The operator can compare data from repeat trips along the hole to understand the borehole stability better.

This is according to C.L. Dalton, M.D. Paulk, and M. Bittar in a paper presented at the SPE annual petroleum conference in Villahermosa, Mexico, in February.

Electrical conductors in the composite coiled-tubing allow data transfer rates at 156 kilobytes per second (kbps) between the downhole components and the surface system, say the authors, allowing the operator to receive all of the data and monitor the petrophysical environment regardless of the drilling activities under way.

This data transfer rate is extremely high compared to the few bps possible from conventional mud-pulse, measurement-while-drilling systems.

Drillers routinely monitor borehole stability using downhole pressure and tension measurements in conjunction with surface injector weight.

Combined with the petrophysical data, the borehole stability data help to identify, prevent, and cure fractures and permeable sands that are responsible for poor borehole stability.

Multiple measurements after drilling passes over the exposed-hole section, over time, tell a petrophysical story about what is happening to the formation environment and borehole stability and is referred to as time-lapse logging.

In the test well at Chocolate Bayou, the composite coiled tubing made more than 30 trips over the openhole section below the casing window, while logging in real time, considerably more than possible with pipe-conveyed drilling.

According to the authors, integration of time-lapse resistivity data and pressure data in a wired composite system allowed engineers to monitor the borehole environment and stability.

It allowed them to identify the best permeability zones for geosteering, isolate potential zones of loss and gains, and identify the propagation of natural fractures and drilling-induced fractures.