Reservoir Characterization Begins at First Contact with the Drill Bit

Reservoir characterization in under-balanced drilling with nonlinear Moving Horizon Estimation with manual and automatic control conditions

“…During UBD operations, reservoir engineers try to estimate the reservoir pressure by employing some flow rate tests. So long as the drilling is done through one reservoir, the reservoir pressure is considered stationary [34,35]. The reservoir pore pressure is assumed to be known, and the estimation of the unknown production index of gas K g and liquid K l from the reservoir into the well is necessary.…”

“…The reservoir pore pressure is assumed to be known, and the estimation of the unknown production index of gas K g and liquid K l from the reservoir into the well is necessary. Some parameters, such as the friction coefficient K f and the choke constant K c are supposed to be known because it is possible to estimate them off-line [34]. Other parameters such as density, temperature, and well volume can be evaluated by well data.…”

“…During drilling through the same reservoir, the reservoir pressure is assumed reasonably homogeneous. Also, the PI increases as progressively larger parts of the production matrix is opened up, and the drilling bit potentially encounters faults [34,35]. The considered scenario is the UBD operation of a vertical well drilled into an oil and gas reservoir, and the reservoir pressure is presumed known.…”