Development of a Doppler Acoustic Imaging System for Borehole Wall to Evaluate Fluid Flow Distribution around Subsurface Fractures

Abstract

We are in the process of developing a doppler borehole televiewer (DBHTV) which quantitatively evaluates the permeability of independent subsurface fractures in a borehole. The system employs an ultrasonic pulsed Doppler method, and is compatible with the conventional acoustic borehole imaging system called borehole televiewer (BHTV). Using the DBHTV, back-scattered waves from fine particles in the borehole fluid such as drill mud or cuttings in a water filled borehole are detected along with the reflected waves from the borehole wall, and the Doppler shift of the back-scattered waves is used to estimate the fluid velocity. A method to estimate the distribution of Doppler shift was examined using a laboratory experimental model. An attempt to locate the sampling volume and a method to quantitatively estimate the flow velocity by scanning the transducer are examined. This study shows that the location of permeable fractures, the distribution of fluid velocity and the fluid volume can be visualized using the DBHTV.

Optimization of Pulsed-Wave Doppler Ultrasound for Estimation of Influx/Efflux in Oil and Gas Boreholes While Drilling Using Conventional Lwd Transducers

“…Although radial flow quantification in production logging may seem similar to influx/efflux while drilling, the speed of rotation of the tool and frequency of ultrasonic probes used in LWD make the direct application of production logging tools to LWD quite challenging. PW Doppler ultrasound has been studied further under laboratory conditions for post-drilling well logging by Saito and Niitsuma (2001) and Monnier and Guillermin (2003). These papers however have not investigated the applicability of the their methods under LWD conditions.…”

Flow Velocity Measurement Using an Orthogonally Radiated Ultrasonic Beam

“…Many physical measurement methods and applications utilizing the Doppler effect have been proposed or implemented in acoustic [1][2][3][4] and optical [5][6][7][8][9] domains. When Doppler flowmetry is applied to the velocity measurement of flow in a pipe, normally the transducer needs to be fixed oblique to the flow as the ultrasonic beam axis has an angular component that is parallel to the flow direction.…”