Deepwater reservoirs are known to have number of challenges associated with operations, evaluation and production potential. The thinly laminated reservoirs, or reservoirs associated with heterogeneous sands could add further challenges. Lateral and vertical continuity of the reservoirs control the real economic potential in many cases. Reservoir fluids and reserve cut-off are crucial information for reservoir development plan, and they are required at early stage during exploration campaign. In order to convert the challenging thinly bedded structures into commercial development potential, proper reservoir characterization with effective cost expenditure becomes critical. Flowing fluid to the surface is usually required for reserve certification as per the Securities and Exchange Commision (SEC) and Society of Petroleum Engineers (SPE) regulations. In many countries, full scale Well Testing is the only way to book the reserve. However, the cost to conduct this operation is quite substantial from few to ten millions of the US dollar depending on the number of testing zones on top of operation complexity. Alternative solution with lower cost is becoming important option, especially in deepwater environments. This paper presents an integrated workflow to use advanced formation evaluation logging information to help building the systematic approach to upscale the Interval Pressure Transient Test (IPTT) to the full scale Well Testing data. The actual field data from South East Asia was used to demonstrate this workflow.
In the first campaign in 2015, number of high resolution logs such as electrical borehole image logs and Nuclear Magnetic Resonance (NMR) logs were acquired prior to fluid identification and fluid sampling using wireline Formation Testers (FT). The IPTT and Vertical Interference Test (VIT) were the secondary objectives. However, the results from the first campaign illustrate an impressive reservoir data that can be obtained from a short pressure build-up after sampling. The vertical connectivity can be seen clearly in the pumping and build-up data. In the second campaign, more than 26 IPTT stations were planned which includes formation pressure, fluid identification, sampling, and pressure transient test with single 3D Radial inflatable packers and the focused sampling probe. The lessons learnt from previous campaign allows us to conduct the test in much more effective time, i.e. within 1-3 hours per station.
Due to complexity of deepwater sedimentations, there are more challenges to understand the flow potential for each tested interval. This is crucial information to derived effective permeability from the IPTT data. Other high resolution logs such as NMR and electrical borehole image logs were used to define bedding boundary. NMR measurement gives information of porosity-permeability, and in addition, rock quality can be estimated from NMR and borehole image logs. Later the log derived permeability will be compared to the upscale IPTT tests. The consistency between different data provides confident level for our upscaling method and workflow. This will be a first paper that present this systematic workflow for the challenging deepwater reservoirs.