The Acquisition and Processing of Vertical Seismic Profile in Horizontal Wells Erb West Field, Sabah, Malaysia

Abstract

Three Vertical Seismic Profiles and one well shoot mere acquired as pari of the EWDP-A revisit-3 horizontal drilling campaign in the Erb West field. The main objective in acquiring this data was to derive a reliable velocity model for the overburden in the main part of the field. By positioning the geophones in the horizontal section, and below the heavily faulted overburden, allowed for correct imaging of reservoirs immediaiely belozu the wellbore and the dipping horizons that subcrop the Shallow Regional Unconformity. Also an attempt will be made to integrate the VSP rcsults with the newly acquired surface 3D seismic to help identify multiple patiems, and to guide the derivation of velocities for stacking and migration. The acquisition involves the deployment of, a 3- component, gimbal-mounted seismic geophone that is drill pipe conveyed into the well. As the tool is pushed into the hole, it is siopped at pre-determined stations, rigidly coupled to the casing, and acoustically isolated from the drillpipe to provide a good signal-to-noise ratio. The seismic source is positioned directly over the sensor, and a serie.s of shots are recorded at euch Station. The main problem with processing VSP data acquired in a horizontal well is the Separation of the upgoing from the downgoing wavefields. In conventional VSP Processing this is accomplished by the geophone being vertically displaced in the wellbore. In the Erb West field, this was accomplished by using the downgoing wavefield obtained over the build up section together with differences in moveout betzoeen the direct arrivals and reflected events from structurally tilted reflectors beneath the horizontal part of the hole. This all ozo ed for the creation of a high resolution seismic image in the vicinity of the well.