Publications

During development drilling of Banyu Urip Field, occasionally, operational challenges prevent acquisition of standard open hole wireline log data. We have become confident that LWD (logging while drilling) tools run to TD (total depth) on drill pipe is a safe and valid method to duplicate most wireline logs in these wells. If encountering uncontrollable mud losses, we must sometimes rely on cased hole logs. In several instances, cased hole neutron porosity logs were acquired to establish the reservoir zonation, model creation, volumetric calculations and perforation zone definition. The cased hole neutron gives a good representation of the relative porosity in the oil zone but the absolute porosity numbers have higher uncertainty than open hole Neutron – Density logs. Another key success criteria of this project is accurate identification of the top of the carbonate reservoir for reservoir description, volumetrics and later definition of the possible highest perforation interval. The top of carbonate is commonly identified from cuttings and open hole logs. However, in some wells, loss zones preclude circulating cuttings to surface and the loss control material applied to the borehole makes log interpretation uncertain. The cased hole Spectral Gamma Ray log shows a clear signature change from the overlying clastics to the carbonate to identify the top of carbonate in cases of no cuttings or poor log quality. The third critical success factor in this drilling campaign is fully cemented perforation zones. In a few wells that were drilled to TD with uncontrolled mud losses, the cement typically only rises to the deepest loss zone, leaving the annulus empty above that. The Cement Bond Log data provides definition of the top of cement which is usually found as predicted near the deepest loss zone. In some cases, perforation intervals are adjusted to avoid perforating into the open liner annulus.