Drilling advances

Nov. 2002 Vol. 223 No. 11  Drilling Advances

Robert E. Snyder,  Executive Engineering Editor

 Hurricane Lili in the U.S. Gulf. Packing 140-150-mph winds while it was offshore, the second hurricane of the season moved north from Cuba to landfall west of Lafayette, Louisiana, on October 3. Once onshore, the storm lost a lot of its punch, still causing extensive damage with winds up to 100 mph. 

 Offshore oil/gas facility operators and drilling contractors conducted a massive evacuation, leaving some 750 platforms and most active rigs vacant. Three mobile offshore rigs were casualties. Rowan’s jackup Rowan-Houston was ripped off its legs and sunk in 105-ft water. Reports indicate it had been struck by another vessel. Diamond Offshore’s Ocean Lexington semi was torn off its moorings, dragged some 45 mi and grounded in 30-ft water – full damage has not yet been estimated. And Nabor’s Dolphin 105, 110-ft jackup, capsized 30 mi offshore in Ship Shoal Block 126. It was found lying on its side in 40-ft water. Early reports said, as of October 7, 116 production platforms were still vacant and four rigs were unmanned, compared to 96 the day after Lili. 

 Inhibitive water-based fluid. The Baroid product service line of Halliburton Energy Services (HES) has developed an inhibitive water-based fluid – HYDRO-GUARD – which is designed for maximum shale inhibition in highly reactive formations like those found in the Gulf of Mexico. Field tested in early 2002, the system provides wellbore stability, high rates of penetration, and acceptable rheological properties over a wide range of temperatures. It has been run successfully in Gulf of Mexico shelf- and deepwater operations. 

 The fluid exhibits stable yield point and gel strength values over the entire range of temperatures normally encountered in deepwater and shelf drilling. This is attributed, in part, to the absence of commercial clay and to the system’s inhibition capabilities. The polymer chemistry that controls rheological properties provides shear-thinning at the bit for fast drilling, yet ensures efficient capture / removal of drill solids. The wellbore remains stable and in-gauge, reducing need for frequent wiper trips. 

 Two unique proprietary polymeric additives minimize shale hydration almost instantaneously. One is a potent flocculant that is effective at low concentrations, allowing the encapsulation of drill solids; the other prevents hydration and disintegration of clay-rich formations, especially in troublesome, gumbo-type formations. During recent drilling of 3,200 ft of 17-in. hole in the GOM, the fluid yielded a low 7.5 methylene blue test, compared to 25-30 MBT for a typical partially hydrolyzed polyacrylamide polymer fluid under equivalent conditions. At the shaker, cuttings appeared crisp and glossy, indicating excellent inhibition. 

 HES says the system is well-suited for rigs with limited deck space, or those operations in eastern areas of the Gulf of Mexico where synthetic base fluids cuttings are not presently permitted for discharge. 

 Bubbles in the mud. Shell reported recently that NAM, a Shell Operating Unit, has been testing, and preparing to use, a new drilling mud containing entrapped air bubbles. Drilling in depleted reservoirs is problematic, in that drilling overbalanced sometimes causes mud loss and damage to the near-wellbore reservoir. However, drilling underbalanced carries the risk of borehole collapse and subsequent well loss. To address this problem, a new-generation drilling mud for use in these conditions called Aphron ICS has been developed by M-I.

 After being aerated at surface, the mud, which contains a surfactant, is pumped into the wellbore. Under normal downhole pressures, the bubbles decrease in size until they encounter the low-pressure of the depleted well. There they expand in the throat of the formation pores, forming a barrier between mud and reservoir. 

 Conventional bubbles have a single-shell construction and, when they contact each other, they join to form a larger bubble. The bubbles within the new mud system have a dual, high-tensile shell so that, when they contact each other, they form a honeycomb structure. The bubbles have a life cycle of about two days before they break down. Once the well is drilled and all mud is removed from the borehole, the remaining bubbles dissolve, unblocking the pores. No special topsides operation or additional equipment is necessary. 

 The Aphron ICS trial in the Netherlands was a first in the Shell Group, and among operators in the North Sea arena. In close cooperation with M-I, the mud was evaluated in an inactive well, then applied successfully in the field across a depleted reservoir. 

 Intelligent drill pipe. Government and industry officials have announced a major innovation that turns drill pipe into a high-speed data transmission tool capable of sending data 100,000 times faster than technology in common use today. The new system, named IntelliPipe, was developed by a team from Grant Prideco and Novatek Engineering, under a project funded by the U.S. Department of Energy. 

 The system comprises drill pipe with built-in telemetry. It can transmit or receive large amounts of data as fast as one million bits per second, giving drillers the first-ever capability to “tell” a drilling tool what to do almost instantaneously. The “smart pipe” has undergone several field tests and is expected to be introduced commercially sometime next year. Grant Prideco and Novatek have formed a marketing JV called IntelliServ. 

 The key to the new system is a unique, non-contacting coupler embedded in connections between the drill pipe joints. The coupler permits data to be sent across the connection and on through a high-speed cable attached to the inner pipe wall.

 Struggling with the problem of a reliable electrical drill pipe connection, in the mid-1970s, developers turned to a technology called “mud pulse telemetry,” which transmits data as pressure pulses through the drill fluid. But the slow pace of 3 to 10 bits per second often meant data resolution was so poor that the driller could not make crucial decisions in real time. 

Now, with a high-speed, bi-directional communications link, a drilling system’s azimuth, inclination, pressure, temperature, loads and vibration, along with information on rock characteristics near the bit, can be evaluated almost instantly. Also, the ability to send high-speed data through the drill pipe may permit technologies once thought unobtainable – such as collecting seismic data at the bit.  

Comments? Write: snyderr@worldoil.com