Abstract

The South Fuwaris Field is located in the Partitioned Zone between Kuwait and Saudi Arabia. The Lower Cretaceous Ratawi reservoirs were discovered in 1961, and production commenced in 1963. There are two major reservoirs – the Ratawi Limestone, which is predominantly developed by vertical wells, and the Ratawi Oolite, which is exclusively developed by horizontal wells. The reservoirs comprise low-moderate permeability limestones.

The use of Logging While Drilling (LWD) tools which utilise natural radioactive sources has been always risky since losing radioactive source will necessitates a complex procedure to abandon side track the hole.

Recently, a new LWD logging technique that incorporates Pulsed Neutron Generators (PNG) was introduced to Wafra Joint Operations (WJO). This new technique acts generates multiple measurements (Resistivity / Density / Neutron / Sigma / Spectroscopy). The PNG uses electrical power generated from the measurement-while-drilling (MWD) turbine to generate a large cloud of fast neutrons. These fast neutrons interact with the formation atoms to generate formation hydrogen index, sigma, and spectroscopy data. In addition, the fast neutron interactions generate a secondary gamma ray cloud that can be used to measure formation density (similar to standard density measurement).

This innovative technique was used for the first time for Wafra Joint Operations in the South Fuwaris Field, with great success. The tool was run in a pilot hole with an inclination of 60°, cutting the Ratawi Limestone and Ratawi Oolite reservoirs. The acquired data were of excellent quality in comparison with conventional LWD data.

The formation sigma was used in the water saturation calculations. Spectroscopy analysis was also recorded and used for formation evaluation, especially for clay content.

Finally, the new technique has been proven as a good risk mitigation / elimination for future operations.

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