Rotary ‘Lie’ Detectors applied to reservoir simulation models – How did we perform?

Abstract

Operations in the highlands of Papua New Guinea (PNG) bring together multidisciplinary teams to explore, develop and produce oil and gas. In the PNG highlands, and prior to an increase in LNG production and ‘field blowdown’, the Development Geology team at Oil Search has identified a series of Oil Fields Expansion (OFX) wells which will extend oil production and add significant reserves, as well as adding valuable information to ‘ground truth’ our static and dynamic models. Two examples are described in this paper where drilling has examined our “lies and truths” as predicted from geological and reservoir simulation modelling. Reservoir simulation work in PNG is vital to assist in the identification of oil opportunities. Static modelling is the core to defining the field volume in place and requires structural geology input to define the reservoir architecture, since well information in the fields is limited and there is only sparse 2D seismic coverage. Therefore, all well data, including, log, core/plug and well tests data and interpretation, are essential as part of the static model built. This ensures that the static model incorporates the characteristics, architecture and behaviour expected of the field/wells. Dynamic simulation evaluates the ground truth of the field extents, including faults orientation, the nature and extent of communication across fault blocks, and the identification of undrained hydrocarbons. Adjustment of the reservoir architecture, characteristics and properties is often involved in numerous, iterative processes between the geologist and reservoir engineer. The Moran field dynamic reservoir simulation work highlighted significant Oil-In-Place volumes not being produced south-east of the Moran 15 ST1 producer. The Moran 15 ST2 well, drilled in July 2019, stepped out ~700m to the south-east and was intended to access these volumes in the Toro C and Digimu reservoirs. A key risk was the existence of faults that may create compartments, whereby the extent or size of the compartment is unknown. The real-time logs, petrophysical analysis and pressure data acquired across the reservoirs suggested both reservoirs are oil bearing. The Toro C and Digimu pressures are in line with that expected for the A Block and confirmed that the Moran 15 ST2 well is in the same compartment as the original Moran 15 well. Further to the south, in the Kutubu complex, maintaining gas injection and continued zonal management has been consistently necessary to reduce declining oil production in the Usano Field. The UDT 15 infill opportunity has been designed to twin the abandoned UDT 4A well that formerly produced ~5 MMstb from the eastern portion of the field. Due to be spudded in August of 2019 within the UDT 4A/6 sub-block, the well will access undrained reserves in Toro B Lower and C reservoirs. Dynamic modelling with emphasis on both production and gas injection in Usano East was important to constrain both the position of bounding faults as well as oil in place. This well will provide key learnings to the accuracy of our predictive reservoir models.

AAPG Datapages/Search and Discovery Article #90371 © 2020 AAPG Asia Pacific Region, The 1st AAPG/EAGE PNG Geosciences Conference, PNG’s Oil and Gas Industry: Maturing Through Exploration and Production, Port Moresby, Papua New Guinea, February 25-27, 2020