Sourceless Porosity-Density and Geomechanics with Logging-While-Drilling Tools in Carbonate Sequences

Abstract

Abstract Azimuthal acoustic logging-while-drilling (LWD) sensors have recently been used in a bottomhole assembly (BHA) to evaluate the viability of sourceless formation evaluation compared to conventional density-neutron data acquired in the same run in a horizontal well across a carbonate sequence. Borehole deterioration and significant pore pressure variations across the reservoir layers pose wellbore stability risks during the drilling phase, which has historically requireddrilling deviated pilot-hole sections for evaluation purposes. These sections were then plugged, backed, and sidetracked. Previous experiences in the same geological setting also encountered extreme borehole enlargements. LWD helped acquire high-quality data before borehole enlargement occurred. Additionally, possible rock anisotropy indications were observed, and rock mechanical moduli were derived. The results were then correlated and normalized to existing field geomechanics knowledge and offset well data. Azimuthal acoustic tools, free of radioactive sources, were run in an LWD tool combination, with the primary objective of measuring porosity, pressure prediction, and possible anisotropy using a four-axis acoustic caliper sensor. This paper discusses the planning, design, and execution of an LWD azimuthal acoustic tool in the case study well. Additionally, the viability, integrity, and robustness of logged data as well as interpreted results are discussed. Optimization of real-time drilling operations and petrophysical dataacquisition requirements are also investigated to help optimize future field development data-acquisition requirements and overall reservoirmanagement strategies.