Oilfield Review April 1989

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Logging While Drilling

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Logging while drilling (LWD), with new tools engineered into drill collars, provides a real-time first look at formations crossed in the well. Resistivity, neutron-density and gamma ray measurements, combined with drilling engineer and geologist optimize drilling decisions. This introduction to Schlumberger’s LWD system covers how it works and how it interfaced with wireline logging.

Cement Chemistry and Additives

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Cement Chemistry

From Humble beginnings in shallow, easy-to-cement wells, cementers now cope routinely with deep wells, weak formations, lost circulation and every other downhole hazard. This article explains how cements sets, and reviews the action of additives used to tailor cement behavior to particular well conditions.

Marine Seismics in Cameroon

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The first in series on marine seismic techniques, this article introduces the basic ingredients of a two dimensional offshore seismic survey—from data acquisition to basic signal processing to interpretation. A recent 2-D survey in the offshore Douala Basin serves as a case study throughout.

Jack Up Rigs: Evolution of Design

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Jack up

Sedco-Forex’s jack up rig, the Trident IX, recently set a water depth record (391 feet; 119 meters) drilling in offshore Angola. We explain the key features of jack up rig design, how to determine a rig’s stability in worst-case weather, and why Trident IX improves on traditional jack up design.

Pulsed-Neutron News

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Pulsed-neutron logging provided the only means of measuring water saturation in cased wells. Oil companies use the technique to monitor reservoir depletion. The log used to be affected by borehole and neutron diffusion effects. Now, with breakthroughs in measurement physics, these affects have been eliminated, dramatically.

The Earth’s Heat

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Earth heat

The oil industry owes everything to radioactive isotopes in the crust and mantle such as potassium-40, thorium-232 and uranium- 238. Decaying over billions of years, these provide 80 percent of the Earth’s heat, driving tectonic movement and cooking organic matter into hydrocarbons.

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