Acknowledging Structural Uncertainty of Gumai Sand Reservoir by Time-Depth Equation of 3D Velocity Modeling for Further Field Development in Tempino Structure, JambiĀ
Author: Chandra Mustofa E.P, Giovanno Leonardo Sihombing, Herbert Sipahutar, Heru Pratama, Ikhsan Novryan Priatama, Reza Rahadian
Pertamina Hulu Rokan, PT. Sigma Cakrawala International
ikhsanovryan@gmail.com
Tempino structure is one of oil and gas structure in Jambi Field. Air Benakat Formation (ABF) have been known as main productive reservoirs. Presently, Gumai Formation (GUF) is main target of development since the latest drilling well showed a fascinating hydrocarbon potential. This managing structural uncertainty review is based on 3D seismic data, standard electrical log, vertical seismic profile, and mud log data. Reservoir evaluation is often conducted in deterministic method thus the uncertainty of associated parameters is still unquantified. Previous subsurface evaluation of Tempino structure was also done in deterministic method, resulting single output of each interpretation then recognized that the new drilling T-204 well had indicating Gumai sand reservoir is 19 meters shallower than estimated. A prompt subsurface modelling then conducted considering parameters possibly causing uncertainty.3D velocity model method is believed to be a main factor in producing 19 meters discrepancy of the latest drilling well result. Vertical seismic profile data is also informing difference velocity in near Gumai sand reservoir level. Latest 3D velocity model is conducted in two version, which are: constant velocity and time-depth equation. All velocity models being assessed by the residual map or the differences between well markers and the converted surfaces across the wells.
The constant velocity model is selected based on its smallest residuals value. This updated velocity model has been made consistent with static model of Gumai sand reservoir, concerning all possibly uncertainty of time to depth conversion parameters. In 2022, 4 wells will be drilled in Tempino about to confirm reliability of the selected velocity model, yet marker adjustment of new well data would be updated to reinforce the depth structure map.
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