Hydraulic Flow Unit Based Permeability Characterization and Rapid Production Prediction Workflow for an Offshore Field, South China Sea

Abstract

This paper presents a case study of hydraulic flow unit (HFU) based permeability characterization and fast production prediction for an offshore field, South China Sea. The aim is to integrate cores, petrophysics logs, formation tester and drill string well test (DST) data together to build a generally applicable workflow for rapid production prediction immediately after logging, in order to facilitate the decision making of the drill stem testing and completion. Overall productivity of a well and productivity of each zone is critical information for well evaluation. Based on a quick yet reliable answer, operators can decide whether the well should be tested by DST /completed. If the prediction is within the acceptable accuracy range, the number of zones to be tested could be reduced. Therefore well cost can be greatly saved. The major challenges are facing in this field are: highly laminated sand/shale sequences, strong heterogeneities, complex porpermeability relationships, and different scales of different measurements. Based on the field geological settings, total four sub areas, two sub zones were delineated. Different HFUs were identified from core data for each area and zone. The porositypermeability models were built in each HFU. The permeability output was calibrated by formation tester interpreted effective permeability to get calibration scale factor. Based on the scale factor, a workflow was then set up to predict the production for new wells, from either core data or petrophysical data, depending on the data availability. Three DST results were used to validate the results from this workflow, giving great confidence of the applicability in the study result (the prediction accuracy is within 20% range). This case study brings following values: a quick production prediction workflow has been set up for this field; and the methodology applied is not limited to this specific field but applicable to other fields with similar formation types.