A Case Study on a Real-Time High-Resolution Formation Evaluation with Deep Transient Testing on Thinly Bedded Reservoirs in Exploration Well: A Net Zero Carbon Emission Well Test Testing Operation
Authors: Nordin T. B. , Abu Talib M. A. , Ong L. W. , Ling C. C. , Motaei E. , Abdullah M. Z. 
Published: February 2024

Thinly bedded reservoirs are increasingly a target of offshore exploration in Malaysia water. Due to the poor physical properties of these reservoirs, simulated production rates were sub-economic, therefore rendering them economically unviable to justify for a Drill Stem Test. This paper describes methods of real-time and high-resolution formation evaluation with formation testing used to characterize such reservoirs. The well testing operation was carried out with innovative non flaring technology (Deep Transient Testing) with wireline latest generation formation tester.

The case study presented demonstrates that the constraints and uncertainty of the conventional measurements can be overcome by multidisciplinary integration by:

Deep Transient Testing provides an environmentally friendly dynamic reservoir characterization operation for thinly laminated sand with zero flaring, reduce emission and energy consumption. Comprehensive integration Tri-axial array induction, high-definition neutron-density-NMR and resistivity borehole image identified the potential hydrocarbon bearing zones in thinly laminated reservoirs. Advanced nuclear magnetic resonance provided key measurements by continuous scanning of the formation properties to correctly identify the reservoir fluid types and estimate fluid saturation and contact. Optical spectroscopy coupled with fluorescence and reflectance measurement with the new generation downhole fluid analyzer identified the full characterization of the formation fluid, both composition and phase behavior. Determination the characteristic of the potential zones using micro-imager tool and allow to estimate textural heterogeneities and define thickness of reservoir zones and borehole geometry.

Basic conventional log measurements with low resolution and conventional DST testing to determine the presence of movable hydrocarbons, qualitative producibility and in situ reserves estimation have been proven to be high-cost operation with inconclusive result due to presence of thin-beds, dispersed clay type and highly variable water salinity. For this case study well, DTT testing was successfully acquired in two thinly laminated oil reservoirs and one gas reservoir. Real time monitoring and uses of high-definition logs at thinly laminated reservoirs (resistivity Rv, Rh, image log sand count, NMR) can reduce the uncertainty in terms of reservoir properties (saturation, porosity, permeability) and fluid typing. In this case study, DTT proved to be a practical alternative to the conventional DST, providing measurements to determine the reservoir dynamic properties (albeit over a smaller test interval), and the acquisition of very low contamination fluid samples for PVT analysis.

The successful implementation of the first deep transient testing oil and gas reservoirs within thin bed sequences with real-time monitoring and the use of high-definition logs at thinly laminated reservoirs can reduce uncertainty in reservoir properties (saturation, porosity, permeability) and fluid typing in Sarawak-Balingian Area, Malaysia.