Petrophysics for Horizontal Wells with Sourceless LWD Technology, A Case Study from Kuwait

Abstract

Abstract In horizontal holes, several factors are affecting formation resistivity. The electromagnetic waves generated from the LWD tools are covering the adjacent beds and the reading can be highly affected. Moreover, when the well trajectory is cutting a bed boundary at a high angle, polarization horns are causing severe noise that masks the true formation resistivity. Recently, several wells in KOC had suffered the above mentioned effects causing great ambiguity in water saturation determination. Moreover, the use of LWD with natural radioactive sources has been always a big concern to KOC. An alternative option to resistivity was proposed to KOC based on using Sigma. The technique incorporates Pulsed Neutron Generators and acts as a multi-purpose measurement (Resistivity / Density / Neutron / Sigma / Spectroscopy). In addition, the technology can be used Sourceless. This technology was used for the first time in Kuwait with great success. The Sigma was used in the water saturation calculations. In addition, a time lapse Sigma was done where a second pass was recorded while pulling out of the hole. A comparison between drilling Sigma and reaming up Sigma was used to indicate any water movement by OBM invasion. Spectroscopy was also used for formation evaluation specially clay content. This is rather useful in complex lithology especially when the Gamma Ray reading is affected by strange mineralogy, thus affecting mobility calculations for accurate ICD design.