Reducing the Appraisal Uncertainty with Advanced Wireline Formation Testing Technology: A Case Study from the Gulf of Thailand

Abstract

AbstractThe paper discusses an application of advanced wireline Formation Testing (FT) technology on an appraisal stage in order to improve an understanding of reservoir characteristics and to assist a field development plan. The advanced FT technology includes a focused sampling probe, a new 3D radial probe, and a new fluid analyser. Further information on tool functionality, real-time data interpretation, and acquisition result is described.Fit-for-purpose wireline FT modules were deployed. The focused sampling probe delivered quicker clean-up for downhole fluid extraction. The new fluid analyser with improved algorithm and more sensors measured fluid properties at downhole condition and also quantified a contamination level prior to capturing a fluid sample. The new 3D radial probe (Saturn Probe), which has the largest flowing area among probe family, enabled fluid pumping and sampling at low mobility zones. An Interval Pressure Transient Test (IPTT) to obtain permeability and skin was also conducted with this new probe. The data acquisition was closely monitored and discussed on real-time.Several wells have been drilled and data was successfully acquired at reasonable operation time. The focused sampling probe, with its unique design, met an objective of providing fast clean-up during pumping formation oil. This was indicated by a sudden change on the fluid analyser's Gas-Oil Ratio (GOR) and other parameters when the probe was in "split the flow" mode and focused. The sudden change was then followed by stable measurements of acquired properties indicating practically minimum contamination level has been achieved. Besides quantifying a contamination level, the new fluid analyser was also able to validate the fluid type which was derived from the pressure points. In addition, its viscosity sensor helped to understand viscosity variation among reservoirs which could not be done with a conventional fluid analyser. The new 3D radial probe maintained pressure drawdown while pumping at low mobility zones. Hence, sand failure that potentially deteriorates tool performance could be avoided. It also had shorter operation time than a conventional packer while conducting IPTT due to less inflating volume and tool storage. The IPTT results showed radial flow regime which was further analysed for permeability and open-hole skin.In an appraisal stage, data acquisition is critical for field development plan and final investment decision. It definitely requires robust and advanced technology that is able to deliver conclusive answer in challenging environment. A case explained here shows how the advanced technology revealed a hydrocarbon potential and confirmed reservoir continuity.