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The improvement is in estimating the confidence interval

Exploration and appraisal well tests At the exploration stage, tests are performed both with an openhole wireline tester, to measure pressures and collect fluid samples, and with the drillstring, to simulate production at the time of the completion. A wireline tester is used to measure the static pressures of all the permeable layers of interest. Pressure versus depth plots help establish the formation fluid gradients and identify the fluid contacts in the reservoir. The MDT tool can also be used with a packer module to perform a smaller-scale production test. A conventional DST is necessary because at the exploration stage the operator needs to know whether the discovery is of commercial value. The objectives are to establish a production rate and the volume of the reservoir. If production rates are low, the operator needs to know if it is because of poor reservoir deliverability or because of a high skin factor. In the latter case, flow rates could be increased if the skin were removed, and the well would have better potential. If the volume of hydrocarbons in place, inferred from the initial test, was too small, the discovery would lose its economic potential even if production rates were high. A primary reason for testing exploration wells is to recover a fluid sample. This is the best stage at which to characterize the reservoir fluid, because the reservoir is in a virgin state and no fluid has been produced. In later stages of a reservoir’s life, the fluid composition changes and the surface fluid composition may not exactly match the downhole fluid composition. (This is especially true in two-phase situations such as condensate reservoirs.) Because the fluid sampling program in an exploration well is particularly important, it will feature both a wireline sampling program (including the collection of PVTquality samples) and larger volumes produced during the DST operation.