Thru-Drill-Pipe Cross-Dipole Array Acoustic Logging Tool Capable of Mapping Deep Shear Wave Reflectors Away from the Wellbore

Abstract Slim cross-dipole tools are available for decades, but recent improvements in high-amplitude acoustic transmitters permit the emission of high energy acoustic waves capable to reflect back to the borehole and map subsurface features. The objective of this work is to present the industry-first deep shear wave imaging results of a thru-drill-pipe x-dipole acoustic tool in North America. The purpose of this technology is to map natural fractures away from the wellbore that do not necessary intersect the borehole for reservoir characterization and effective wellbore completion decisions. The deep shear wave processing of cross-dipole data from slim tools is very similar of raw full-wave form data from a large diameter wireline tool. The processing workflow includes deconvolution, filtering direct waves, up-going / down-going wave separation, and reflected signal stacking. The deconvolution of the raw data is performed to enhance the signal-to-noise ratio of the reflections. The M-filtering of direct wave modes is for cleaning the early arrival of the flexural dipole, refracted Leaky-P. and borehole-guided Stoneley waves. The wave separation is conducted by processing the receiver array full-wave forms and the transmitter array full-wave forms. The reflected images are then created by common mid-point (CMP) stacking and dip move-out (DMO) stacking. One difference in slim tool data acquisition is the variety of deployment methods, (through drill-pipe, coiled-tubing, wireline, slickline, tractor, and pump down); therefore, the depth reference could be acquired in different ways. The deep shear wave imaging results from a 4-component cross-dipole data acquired by 2 ¼ inch diameter tool clearly identify natural fractures 40 to 50 ft deep into the reservoir that do not intercept the borehole. Two clear fracture zones are identified from the thru-drill-pipe x-dipole data acquired under logging challenging conditions. The identification of natural fracture zones allows reservoir engineers to decide landing intervals for horizontal wells into specific mechanical stratigraphic sweet spots defined by the presence of fracture corridors. Deep shear wave imaging provides critical subsurface information to accurately characterize natural fracture zones for multi-stage stimulation of horizontal wells. Slim logging x-dipole tools also allow versatile conveyance methods to accurate determine mechanical properties, azimuthal anisotropy and clear subsurface reflector mapping away from the wellbore.