Fluid and Reservoir Characterization from Wireline Formation Tester: FieldExamples from Santos Basin Reservoir

摘要

The objective of this study is to dynamically characterize the reservoir and fluid distribution in a SantosBasin field by using well data including in-situ fluid properties and dynamic reservoir properties fromwireline formation tester(WFT),openhole logs,and a simplified structural model of the field.Reservoirpressure measurement,pressure gradients,and fluid identification and sampling are part of the routinewireline suite service to evaluate offshore wells.The ability to extract high-quality reservoir propertiesfrom interval pressure transient tests(IPTT)and to measure fluid properties in real time are critical tocharacterizing laminated reservoirs in early stages,before production tests.The challenge of characterizing the reservoir and downhole fluid in different intervals of the reservoir aswell as assessing reservoir connectivity in early stages of the field evaluation is ably addressed by deployingthe latest WFT technologies,including radial probes entry for higher-quality interval IPTT and downholefluid properties measurement.These measurements and methodology using a dissolved-asphaltene equationof state(EOS)enabled the investigation of compartmentalization or lack of thermodynamic equilibrium insome of the reservoir intervals,providing information for future well data acquisition and field planningdecisions.Among downhole fluid measurements,optical density of the formation fluid linearly correlateswith reservoir fluid asphaltene content,which in combination with a gas-liquid-asphaltene equilibriamodeling enables operators to reduce uncertainty in reservoir connectivity assessment.Different fluid unitswere identified,on top of each other and most probably disconnected from each other.The technique usedis based on comparing the fluid coloration of different collected samples that could be in communicationto establish if they could be in equilibrium(same fluid unit)or not.From an understanding of the fluid distribution and permeabilities of the field,reservoir scenarios aredeveloped to optimize and design future well data acquisition and to improve field development plans.