Enhancement of Vorwata Field Reservoir Model by Integration of Pressure Transient Analysis with Real-Time Downhole Pressure Data
- Agus Setiawan (BP Indonesia) | Kirk Hird (BP) | Curtis Owen Bennett (BP Berau Ltd)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 20-22 September, Jakarta, Indonesia
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 4.6.2 Liquified Natural Gas (LNG), 5.1 Reservoir Characterisation, 3.3.6 Integrated Modeling, 2.2.2 Perforating, 4.2 Pipelines, Flowlines and Risers, 2.4.3 Sand/Solids Control, 5.1.2 Faults and Fracture Characterisation, 5.5.8 History Matching, 3 Production and Well Operations, 5.6.3 Pressure Transient Testing, 4.1.5 Processing Equipment, 6.1.5 Human Resources, Competence and Training, 5.1.1 Exploration, Development, Structural Geology, 4.6 Natural Gas, 5.6.11 Reservoir monitoring with permanent sensors, 5.6.4 Drillstem/Well Testing, 5.1.7 Seismic Processing and Interpretation, 2.7.1 Completion Fluids, 4.1.2 Separation and Treating, 1.6 Drilling Operations, 2 Well Completion, 4.3.4 Scale
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Vorwata is a giant gas field located in Bintuni Bay, Papua Barat Province, Indonesia. The field was discovered in 1997 and currently produces approximately 1.3 bcf/d of dry gas from the Roabiba sandstone reservoir. Initial development consists of 14 wells drilled from two platforms. The wells produce through 7-inch tubing and have been tested up to 240 mmscf/d. A Permanent Downhole Pressure Sensor (PDPS) is installed in each well to continuously monitor downhole pressure and temperature.
Vorwata field is a faulted, high sand quality reservoir. The impact of faults on reservoir performance was very uncertain prior to startup. There was great concern the field could be compartmentalized, or at least strongly influenced by flow baffles and barriers. One of the primary subsurface objectives during pre-startup testing was to assess lateral and vertical reservoir connectivity within the development area.
Pressure build-up tests (PBU) were conducted in each well as part of the initial clean up and testing procedure. The initial tests were very helpful in characterizing offset faults. PBUs obtained once the field was put on production are influenced by interference from offset wells, masking any boundary effects. Interpretation of the PBUs is enhanced by applying deconvolution. A pre-startup interference test successfully identified lateral and vertical pressure communication within the development area. The well/fault geometries and reservoir connectivity characteristics obtained from the PBUs and interference test have been used to condition the static and dynamic models.
This paper describes the well testing program that has been implemented to reduce reservoir uncertainty in the Vorwata reservoir during the early phase of field development. Well test and pressure interference results have been integrated into full-field models to better assess future field performance and development decisions.
Vorwata is the largest gas field within the Tangguh Joint Venture area. The field began production in 2008. The initial development consists of 14 wells drilled from two platforms. Produced gas is delivered to an onshore LNG plant facility, liquified and then transported to the Asian and North America gas markets. Additional resource potential exists within Vorwata and other Tangguh fields, possibly requiring a third LNG train. The timing of end of plateau of the current development and the required size of the next development are the two most important questions that need to be answered as early as possible. To help answer these questions, a surveillance plan was developed. Pressure buildup tests (PBUs) were obtained during initial cleanup to estimate initial reservoir pressure, permeability, skin and also to characterize boundaries and baffles. In addition, a pre-startup interference test was run to develop an understanding of lateral and vertical reservoir connectivity.
Reservoir Characterization Using Well Testing
Well testing is one of the main techniques used in the oil and gas industry to assess well performance and characterize reservoirs. Well testing measures the dynamic reservoir behavior in response to changing flow conditions at the well. The dynamic response of the well pressure to a change in rate is dependent on reservoir and well properties. Hence, studying the dynamic pressure behavior in response to an appropriately designed sequence of well rate changes provides a way to evaluate some of these properties. This technique historically has been used for evaluation of formation permeability, large-scale reservoir heterogeneities, boundaries, reservoir connectivity and well productivity.
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