Running LWD Azimuthal Sonic and Azimuthal Density in Tandem Confirms the Azimuthal Sonic Technology for Real Time Dip Picking and Geosteering Application. Middle East Case Study

Abstract

Proper Well Placement in multi layers thin carbonate reservoir could be challenging due to high geological uncertainty. Using radioactive sources to evaluate porosity & formation dipping is effective, but considering the drilling environment & high risk to get stuck makes a lot of restrictions on using of the nuclear tools. This paper is a case study illustrating utilizing absolutely sourceless azimuthal sonic in a comparison with conventional radioactive density as a highly effective alternative sourceless geosteering method & adds extra formation evaluation values.

The technique provides azimuthal sonic data were acquired with a focused unipole tool which recorded the measured waveforms and computed Compressional and Shear velocities in 16 azimuthal bins yet Quadrant Compressional and Shear slowness were computed by stacking all 16 bins of data in Realtime, which gave very high signal-to-noise ratios and excellent data quality. The azimuthal Quadrant real-time sonic porosities were effectively used to well placement in the target reservoir, later on the full 16 bin azimuthal memory were examined to understand the additional advantages of using the azimuthal sonic even before approaching the main bed boundaries.

Both of Azimuthal Density & Azimuthal Sourceless Sonic measurements were able to detect the boundaries of the target zone, allowing accurate stratigraphic interpretation as well as dip picking calculation to ensure proactive geosteering and maintain the well trajectory as per the plan. It was proven that the Sonic lengthy depth of detection can add an additional safety margin to enable adjusting the well trajectory in the reservoir at the optimal angle, the comparison chanced later against the Azimuthal density image was matching very well and emphasised the formation dipping.

This case study proves the capability of using LWD Azimuthal sonic as an effective & alternative sourceless porosity for geosteering and formation dipping calculation purposes.

Introduction

The case study illustrates our experience in drilling & geosteer horizontal well multi-layers thin reservoir in a Lower Cretaceous carbonate field in Abu Dhabi using LWD real-time azimuthal sonic technology in comparison with azimuthal density image.