Formation Testing and Sampling Using an Oval Pad in Al Hamd Field, Egypt

Abstract

Abstract Carbonate rocks, thinly bedded sands and naturally fractured reservoirs can exhibit a very challenging logging environment when pressure testing and fluid sampling are required. The challenge is due to, at least, reservoir heterogeneity, the nature of matrix and secondary pore systems, and the difficulty of sealing the probes on testing tools. An Oval Pad was introduced to help overcome all of these challenges. The Oval Pad covers a vertical section of the well bore, giving it the sealing advantages of a straddle packer but still maintaining the operational flexibility of a probe. In particular, the Oval Pad design ensures an effective seal for the probe during formation testing and fluid sampling in the presence of vuggy and/or fractured carbonate rocks. In addition to the increased vertical sealing area, the oval shape can reduce the sampling time due to a focusing effect the pad has on near-wellbore flow. A multiphase simulator is used to demonstrate this effect in homogeneous and layered zones. Simulations show that when the complete testing system performance is considered, the Oval Pad reduces pumping times compared to a standard probe. Field examples from a Miocene Nullipore carbonate reservoir in the Al Hamd field in the Gulf of Suez are used to demonstrate the applications of the Oval Pad. The wireline micro-resistivity imager was also used to help characterize the zone and to facilitate test point identification. This field data is compared to numerical simulations to show the advantages of the Oval Pad design over both standard probes and straddle packer options. Examples included demonstrate the value of integrating both imaging and pressure sampling data into the overall petrophysical understanding of reservoir characteristics.