Downhole Formation Fluid Identification in a Mature Multi-Layer Reservoir: A Case Study of an Advanced Wireline Formation Tester and Operational Practices for Highly Depleted Reservoir Evaluation

摘要

The highly complex, stacked and multi-layered gas reservoirsrnfound in the Mahakam delta of East Kalimantan present arnchallenge for both drilling and formation evaluation. Many ofrnthe mature producing reservoir layers are at low pressurerntoday; but the presence of certain over-pressured intervalsrnmeans drilling is essential with high mud weights. Drillingrnwith high mud weights can lead to high differential pressures,rnas much as 5000 psi, between the wellbore mud system andrnthe formation fluid pressures. A significant part of thernformation evaluation in the Kutei basin requires formationrnfluid identification using a pumpout wireline formation testerrn(PWFT). The primary objectives are to obtain a measurementrnof the formation pressure, identification of the formationrnfluids, and the determination of fluid mobility. The PWFT toolrnoperates by controlled pumping of formation fluid from arnsample probe, which is positioned adjacent to the reservoirrninterval, through a fluid analyzer and out to the wellbore.rnFluid property measurements and filtrate contamination andrnidentification are accomplished with a new MagneticrnResonance Imaging Laboratory (MRILab™) fluid analyzer.rnDue to the difficult conditions encountered in the Mahakamrndelta, the sampling times ordinarily required to pumpout andrncollect uncontaminated PVT samples were not possible. Thisrnpaper demonstrates the techniques that were developed wherernthe MRILab could quickly identify the formation fluid in siturnwhile pumping and eliminate the need to collect and retrieve arnsample.rnIn this paper, we use field examples from operationsrninvolving the Reservoir Description Tool (RDT™) and thernMRILab™. The RDT tool employs new features that enablernenhanced operational practices to improve formation testing inrnthis difficult environment. The tool features demonstrated inrnthis paper include dual probes vertically spaced seven inchesrnapart with isolation valves and independent pressure gaugesrnfor each probe, a new pump module that can operate up torn6000 psi differential, and an MRILab fluid analysis module.rnOperational practices discussed include preventing toolrnplugging, faster testing in tight zones, and precise toolrnpositioning.