Unearthing New Layers - Crosswell Seismic Redefines Seismic Imaging in Bunyu Field, Indonesia

Abstract

Surface seismic is fundamental information for reservoir mapping and in-fill drilling decisions. A good seismic is critical to successful development of a field. However, at times, the surface seismic is of degraded quality due to various reasons which makes the mapping and interpretation of the reservoir layers difficult and uncertain. Near-surface conditions such as topography, weathering layer adversely affect the surface seismic data acquisition & processing. In Bunyu field in Indonesia, problem is further compounded by the presence of near surface coal seams which renders seismic to be of poor quality. In order to optimize the field development and boost recovery, enhanced seismic is seen as a fundamental requirement to make informed in-fill drilling decisions. Crosswell seismic provides high resolution imaging of the subsurface at the reservoir scale. The technology is used for delineating complex structure. It is not affected by the surface conditions as the transmitter and receivers are deployed downhole in separate wells, providing velocity tomogram and reflection imaging between the wells. Bunyu Field in East Kalimantan is on production since 1950 with declining production over the years. It is primarily a discontinuous sand-shale sequence with shallow coal layers. The existing 3D seismic is of poor quality which makes reservoir interpretation very uncertain. It is difficult to map these channel sands due to poor seismic. Crosswell seismic was thus acquired to complement the 3D seismic information for informed infill drilling decisions and field optimization. Crosswell seismic has provided a dramatic improvement in seismic imaging even at large interwell distances and will be helpful in delineating reservoir and ultimately aid in better in-fill drilling.