Drilling of multilateral wells has increased significantly during the past few years, as one of the reservoir development strategies to maximize well productivity by maximizing reservoir contact (MRC). These complex wells present significant challenges with respect to well accessibility for rigless well intervention. Means of access have been developed to enable conventional coiled tubing (CT) operations such as reservoir stimulation. However, one of the remaining challenges is to run production logs in these wells, to quantify the oil and water contributions of each lateral and to locate fluid entry points; these laterals need to be accessed selectively and identified accurately.

Shortly after being put on production, an openhole multilateral oil producer, drilled in a carbonate reservoir onshore Saudi Arabia, began to produce large amounts of water. Each lateral needed to be logged to identify the source of the water, so that proper remedial action could be taken and the optimal recompletion determined.

At present, there is no production logging tool that can be used independently to log each lateral selectively. A multilateral tool was combined with a compact, integrated production logging tool and a reservoir saturation tool to access the laterals. The pulsed neutron log provided the produced water velocity and water holdup in each lateral; combination of this data with three-phase velocity distribution and holdup logs allowed the determination of fluid flow profiles and identification of water breakthrough intervals.

Careful planning and execution of the logging job included techniques that were employed to overcome challenges and acquire the best possible data on each lateral.